This is groff, produced by makeinfo version 4.6 from ./groff.texinfo.

This manual documents GNU `troff' version 1.19.

   Copyright (C) 1994-2000, 2001, 2002, 2003, 2004 Free Software
Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.1 or any later version published by the Free Software
     Foundation; with no Invariant Sections, with the Front-Cover texts
     being `A GNU Manual," and with the Back-Cover Texts as in (a)
     below.  A copy of the license is included in the section entitled
     `GNU Free Documentation License."

     (a) The FSF's Back-Cover Text is: `You have freedom to copy and
     modify this GNU Manual, like GNU software.  Copies published by
     the Free Software Foundation raise funds for GNU development."
   
INFO-DIR-SECTION Typesetting
START-INFO-DIR-ENTRY
* Groff: (groff).               The GNU troff document formatting system.
END-INFO-DIR-ENTRY


File: groff,  Node: Top,  Next: Introduction,  Prev: (dir),  Up: (dir)

GNU troff
*********

This manual documents GNU `troff' version 1.19.

   Copyright (C) 1994-2000, 2001, 2002, 2003, 2004 Free Software
Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.1 or any later version published by the Free Software
     Foundation; with no Invariant Sections, with the Front-Cover texts
     being `A GNU Manual," and with the Back-Cover Texts as in (a)
     below.  A copy of the license is included in the section entitled
     `GNU Free Documentation License."

     (a) The FSF's Back-Cover Text is: `You have freedom to copy and
     modify this GNU Manual, like GNU software.  Copies published by
     the Free Software Foundation raise funds for GNU development."
   
* Menu:

* Introduction::
* Invoking groff::
* Tutorial for Macro Users::
* Macro Packages::
* gtroff Reference::
* Preprocessors::
* Output Devices::
* File formats::
* Installation::
* Copying This Manual::
* Request Index::
* Escape Index::
* Operator Index::
* Register Index::
* Macro Index::
* String Index::
* Glyph Name Index::
* Font File Keyword Index::
* Program and File Index::
* Concept Index::


File: groff,  Node: Introduction,  Next: Invoking groff,  Prev: Top,  Up: Top

Introduction
************

GNU `troff' (or `groff') is a system for typesetting documents.
`troff' is very flexible and has been in existence (and use) for about
3 decades.  It is quite widespread and firmly entrenched in the UNIX
community.

* Menu:

* What Is groff?::
* History::
* groff Capabilities::
* Macro Package Intro::
* Preprocessor Intro::
* Output device intro::
* Credits::


File: groff,  Node: What Is groff?,  Next: History,  Prev: Introduction,  Up: Introduction

What Is `groff'?
================

`groff' belongs to an older generation of document preparation systems,
which operate more like compilers than the more recent interactive
WYSIWYG(1) (*note What Is groff?-Footnote-1::) systems.  `groff' and
its contemporary counterpart, TeX, both work using a "batch" paradigm:
The input (or "source") files are normal text files with embedded
formatting commands.  These files can then be processed by `groff' to
produce a typeset document on a variety of devices.

   Likewise, `groff' should not be confused with a "word processor",
since that term connotes an integrated system that includes an editor
and a text formatter.  Also, many word processors follow the WYSIWYG
paradigm discussed earlier.

   Although WYSIWYG systems may be easier to use, they have a number of
disadvantages compared to `troff':

   * They must be used on a graphics display to work on a document.

   * Most of the WYSIWYG systems are either non-free or are not very
     portable.

   * `troff' is firmly entrenched in all UNIX systems.

   * It is difficult to have a wide range of capabilities available
     within the confines of a GUI/window system.

   * It is more difficult to make global changes to a document.

     "GUIs normally make it simple to accomplish simple actions and
     impossible to accomplish complex actions."  -Doug Gwyn (22/Jun/91
     in `comp.unix.wizards')


File: groff,  Node: What Is groff?-Footnotes,  Up: What Is groff?

   (1) What You See Is What You Get


File: groff,  Node: History,  Next: groff Capabilities,  Prev: What Is groff?,  Up: Introduction

History
=======

`troff' can trace its origins back to a formatting program called
`runoff', written by J. E. Saltzer, which ran on MIT's CTSS operating
system in the mid-sixties.  This name came from the common phrase of
the time "I'll run off a document."  Bob Morris ported it to the 635
architecture and called the program `roff' (an abbreviation of
`runoff').  It was rewritten as `rf' for the PDP-7 (before having
UNIX), and at the same time (1969), Doug McIllroy rewrote an extended
and simplified version of `roff' in the BCPL programming language.

   The first version of UNIX was developed on a PDP-7 which was sitting
around Bell Labs.  In 1971 the developers wanted to get a PDP-11 for
further work on the operating system.  In order to justify the cost for
this system, they proposed that they would implement a document
formatting system for the AT&T patents division.  This first formatting
program was a reimplementation of McIllroy's `roff', written by
J. F. Ossanna.

   When they needed a more flexible language, a new version of `roff'
called `nroff' ("Newer `roff'") was written.  It had a much more
complicated syntax, but provided the basis for all future versions.
When they got a Graphic Systems CAT Phototypesetter, Ossanna wrote a
version of `nroff' that would drive it.  It was dubbed `troff', for
"typesetter `roff'", although many people have speculated that it
actually means "Times `roff'" because of the use of the Times font
family in `troff' by default.  As such, the name `troff' is pronounced
`t-roff' rather than `trough'.

   With `troff' came `nroff' (they were actually the same program
except for some `#ifdef's), which was for producing output for line
printers and character terminals.  It understood everything `troff'
did, and ignored the commands which were not applicable (e.g. font
changes).

   Since there are several things which cannot be done easily in
`troff', work on several preprocessors began.  These programs would
transform certain parts of a document into `troff', which made a very
natural use of pipes in UNIX.

   The `eqn' preprocessor allowed mathematical formulae to be specified
in a much simpler and more intuitive manner.  `tbl' is a preprocessor
for formatting tables.  The `refer' preprocessor (and the similar
program, `bib') processes citations in a document according to a
bibliographic database.

   Unfortunately, Ossanna's `troff' was written in PDP-11 assembly
language and produced output specifically for the CAT phototypesetter.
He rewrote it in C, although it was now 7000 lines of uncommented code
and still dependent on the CAT.  As the CAT became less common, and was
no longer supported by the manufacturer, the need to make it support
other devices became a priority.  However, before this could be done,
Ossanna was killed in a car accident.

   So, Brian Kernighan took on the task of rewriting `troff'.  The
newly rewritten version produced device independent code which was very
easy for postprocessors to read and translate to the appropriate
printer codes.  Also, this new version of `troff' (called `ditroff' for
"device independent `troff'") had several extensions, which included
drawing functions.

   Due to the additional abilities of the new version of `troff',
several new preprocessors appeared.  The `pic' preprocessor provides a
wide range of drawing functions.  Likewise the `ideal' preprocessor did
the same, although via a much different paradigm.  The `grap'
preprocessor took specifications for graphs, but, unlike other
preprocessors, produced `pic' code.

   James Clark began work on a GNU implementation of `ditroff' in
early 1989.  The first version, `groff' 0.3.1, was released June 1990.
`groff' included:

   * A replacement for `ditroff' with many extensions.

   * The `soelim', `pic', `tbl', and `eqn' preprocessors.

   * Postprocessors for character devices, POSTSCRIPT, TeX DVI, and
     X Windows.  GNU `troff' also eliminated the need for a separate
     `nroff' program with a postprocessor which would produce ASCII
     output.

   * A version of the `me' macros and an implementation of the `man'
     macros.

   Also, a front-end was included which could construct the, sometimes
painfully long, pipelines required for all the post- and preprocessors.

   Development of GNU `troff' progressed rapidly, and saw the additions
of a replacement for `refer', an implementation of the `ms' and `mm'
macros, and a program to deduce how to format a document (`grog').

   It was declared a stable (i.e. non-beta) package with the release of
version 1.04 around November 1991.

   Beginning in 1999, `groff' has new maintainers (the package was an
orphan for a few years).  As a result, new features and programs like
`grn', a preprocessor for gremlin images, and an output device to
produce HTML output have been added.


File: groff,  Node: groff Capabilities,  Next: Macro Package Intro,  Prev: History,  Up: Introduction

`groff' Capabilities
====================

So what exactly is `groff' capable of doing?  `groff' provides a wide
range of low-level text formatting operations.  Using these, it is
possible to perform a wide range of formatting tasks, such as
footnotes, table of contents, multiple columns, etc.  Here's a list of
the most important operations supported by `groff':

   * text filling, adjusting, and centering

   * hyphenation

   * page control

   * font and glyph size control

   * vertical spacing (e.g. double-spacing)

   * line length and indenting

   * macros, strings, diversions, and traps

   * number registers

   * tabs, leaders, and fields

   * input and output conventions and character translation

   * overstrike, bracket, line drawing, and zero-width functions

   * local horizontal and vertical motions and the width function

   * three-part titles

   * output line numbering

   * conditional acceptance of input

   * environment switching

   * insertions from the standard input

   * input/output file switching

   * output and error messages


File: groff,  Node: Macro Package Intro,  Next: Preprocessor Intro,  Prev: groff Capabilities,  Up: Introduction

Macro Packages
==============

Since `groff' provides such low-level facilities, it can be quite
difficult to use by itself.  However, `groff' provides a "macro"
facility to specify how certain routine operations (e.g. starting
paragraphs, printing headers and footers, etc.)  should be done.  These
macros can be collected together into a "macro package".  There are a
number of macro packages available; the most common (and the ones
described in this manual) are `man', `mdoc', `me', `ms', and `mm'.


File: groff,  Node: Preprocessor Intro,  Next: Output device intro,  Prev: Macro Package Intro,  Up: Introduction

Preprocessors
=============

Although `groff' provides most functions needed to format a document,
some operations would be unwieldy (e.g. to draw pictures).  Therefore,
programs called "preprocessors" were written which understand their own
language and produce the necessary `groff' operations.  These
preprocessors are able to differentiate their own input from the rest
of the document via markers.

   To use a preprocessor, UNIX pipes are used to feed the output from
the preprocessor into `groff'.  Any number of preprocessors may be used
on a given document; in this case, the preprocessors are linked
together into one pipeline.  However, with `groff', the user does not
need to construct the pipe, but only tell `groff' what preprocessors to
use.

   `groff' currently has preprocessors for producing tables (`tbl'),
typesetting equations (`eqn'), drawing pictures (`pic' and `grn'), and
for processing bibliographies (`refer').  An associated program which
is useful when dealing with preprocessors is `soelim'.

   A free implementation of `grap', a preprocessor for drawing graphs,
can be obtained as an extra package; `groff' can use `grap' also.

   There are other preprocessors in existence, but, unfortunately, no
free implementations are available.  Among them are preprocessors for
drawing mathematical pictures (`ideal') and chemical structures
(`chem').


File: groff,  Node: Output device intro,  Next: Credits,  Prev: Preprocessor Intro,  Up: Introduction

Output Devices
==============

`groff' actually produces device independent code which may be fed into
a postprocessor to produce output for a particular device.  Currently,
`groff' has postprocessors for POSTSCRIPT devices, character terminals,
X Windows (for previewing), TeX DVI format, HP LaserJet 4 and Canon LBP
printers (which use CAPSL), and HTML.


File: groff,  Node: Credits,  Prev: Output device intro,  Up: Introduction

Credits
=======

Large portions of this manual were taken from existing documents, most
notably, the manual pages for the `groff' package by James Clark, and
Eric Allman's papers on the `me' macro package.

   The section on the `man' macro package is partly based on Susan G.
Kleinmann's `groff_man' manual page written for the Debian GNU/Linux
system.

   Larry Kollar contributed the section in the `ms' macro package.


File: groff,  Node: Invoking groff,  Next: Tutorial for Macro Users,  Prev: Introduction,  Up: Top

Invoking `groff'
****************

This section focuses on how to invoke the `groff' front end.  This
front end takes care of the details of constructing the pipeline among
the preprocessors, `gtroff' and the postprocessor.

   It has become a tradition that GNU programs get the prefix `g' to
distinguish it from its original counterparts provided by the host (see
*Note Environment::, for more details).  Thus, for example, `geqn' is
GNU `eqn'.  On operating systems like GNU/Linux or the Hurd, which
don't contain proprietary versions of `troff', and on
MS-DOS/MS-Windows, where `troff' and associated programs are not
available at all, this prefix is omitted since GNU `troff' is the only
used incarnation of `troff'.  Exception: `groff' is never replaced by
`roff'.

   In this document, we consequently say `gtroff' when talking about
the GNU `troff' program.  All other implementations of `troff' are
called AT&T `troff' which is the common origin of all `troff' derivates
(with more or less compatible changes).  Similarly, we say `gpic',
`geqn', etc.

* Menu:

* Groff Options::
* Environment::
* Macro Directories::
* Font Directories::
* Paper Size::
* Invocation Examples::


File: groff,  Node: Groff Options,  Next: Environment,  Prev: Invoking groff,  Up: Invoking groff

Options
=======

`groff' normally runs the `gtroff' program and a postprocessor
appropriate for the selected device.  The default device is `ps' (but
it can be changed when `groff' is configured and built).  It can
optionally preprocess with any of `gpic', `geqn', `gtbl', `ggrn',
`grap', `grefer', or `gsoelim'.

   This section only documents options to the `groff' front end.  Many
of the arguments to `groff' are passed on to `gtroff', therefore those
are also included.  Arguments to pre- or postprocessors can be found in
*Note Invoking gpic::, *Note Invoking geqn::, *Note Invoking gtbl::,
*Note Invoking ggrn::, *Note Invoking grefer::, *Note Invoking
gsoelim::, *Note Invoking grotty::, *Note Invoking grops::, *Note
Invoking grohtml::, *Note Invoking grodvi::, *Note Invoking grolj4::,
*Note Invoking grolbp::, and *Note Invoking gxditview::.

   The command line format for `groff' is:


     groff [ -abceghilpstvzCEGNRSUVXZ ] [ -FDIR ] [ -mNAME ]
           [ -TDEF ] [ -fFAM ] [ -wNAME ] [ -WNAME ]
           [ -MDIR ] [ -dCS ] [ -rCN ] [ -nNUM ]
           [ -oLIST ] [ -PARG ] [ -LARG ] [ -IDIR ]
           [ FILES... ]

   The command line format for `gtroff' is as follows.


     gtroff [ -abcivzCERU ] [ -wNAME ] [ -WNAME ] [ -dCS ]
            [ -fFAM ] [ -mNAME ] [ -nNUM ]
            [ -oLIST ] [ -rCN ] [ -TNAME ]
            [ -FDIR ] [ -MDIR ] [ FILES... ]

Obviously, many of the options to `groff' are actually passed on to
`gtroff'.

   Options without an argument can be grouped behind a single `-'.  A
filename of `-' denotes the standard input.  It is possible to have
whitespace between an option and its parameter.

   The `grog' command can be used to guess the correct `groff' command
to format a file.

   Here's the description of the command-line options:

`-h'
     Print a help message.

`-e'
     Preprocess with `geqn'.

`-t'
     Preprocess with `gtbl'.

`-g'
     Preprocess with `ggrn'.

`-G'
     Preprocess with `grap'.

`-p'
     Preprocess with `gpic'.

`-s'
     Preprocess with `gsoelim'.

`-c'
     Suppress color output.

`-R'
     Preprocess with `grefer'.  No mechanism is provided for passing
     arguments to `grefer' because most `grefer' options have
     equivalent commands which can be included in the file.  *Note
     grefer::, for more details.

     Note that `gtroff' also accepts a `-R' option, which is not
     accessible via `groff'.  This option prevents the loading of the
     `troffrc' and `troffrc-end' files.

`-v'
     Make programs run by `groff' print out their version number.

`-V'
     Print the pipeline on `stdout' instead of executing it.  If
     specified more than once, print the pipeline on `stderr' and
     execute it.

`-z'
     Suppress output from `gtroff'.  Only error messages are printed.

`-Z'
     Do not postprocess the output of `gtroff'.  Normally `groff'
     automatically runs the appropriate postprocessor.

`-PARG'
     Pass ARG to the postprocessor.  Each argument should be passed
     with a separate `-P' option.  Note that `groff' does not prepend
     `-' to ARG before passing it to the postprocessor.

`-l'
     Send the output to a spooler for printing.  The command used for
     this is specified by the `print' command in the device description
     file (see *Note Font Files::, for more info).  If not present,
     `-l' is ignored.

`-LARG'
     Pass ARG to the spooler.  Each argument should be passed with a
     separate `-L' option.  Note that `groff' does not prepend a `-' to
     ARG before passing it to the postprocessor.  If the `print'
     keyword in the device description file is missing, `-L' is ignored.

`-TDEV'
     Prepare output for device DEV.  The default device is `ps', unless
     changed when `groff' was configured and built.  The following are
     the output devices currently available:

    `ps'
          For POSTSCRIPT printers and previewers.

    `dvi'
          For TeX DVI format.

    `X75'
          For a 75dpi X11 previewer.

    `X75-12'
          For a 75dpi X11 previewer with a 12pt base font in the
          document.

    `X100'
          For a 100dpi X11 previewer.

    `X100-12'
          For a 100dpi X11 previewer with a 12pt base font in the
          document.

    `ascii'
          For typewriter-like devices using the (7-bit) ASCII character
          set.

    `latin1'
          For typewriter-like devices that support the Latin-1
          (ISO 8859-1) character set.

    `utf8'
          For typewriter-like devices which use the Unicode (ISO 10646)
          character set with UTF-8 encoding.

    `cp1047'
          For typewriter-like devices which use the EBCDIC encoding IBM
          cp1047.

    `lj4'
          For HP LaserJet4-compatible (or other PCL5-compatible)
          printers.

    `lbp'
          For Canon CAPSL printers (LBP-4 and LBP-8 series laser
          printers).

    `html'
          To produce HTML output.  Note that the HTML driver consists
          of two parts, a preprocessor (`pre-grohtml') and a
          postprocessor (`post-grohtml').

     The predefined `gtroff' string register `.T' contains the current
     output device; the read-only number register `.T' is set to 1 if
     this option is used (which is always true if `groff' is used to
     call `gtroff').  *Note Built-in Registers::.

     The postprocessor to be used for a device is specified by the
     `postpro' command in the device description file.  (*Note Font
     Files::, for more info.)  This can be overridden with the `-X'
     option.

`-X'
     Preview with `gxditview' instead of using the usual postprocessor.
     This is unlikely to produce good results except with `-Tps'.

     Note that this is not the same as using `-TX75' or `-TX100' to
     view a document with `gxditview': The former uses the metrics of
     the specified device, whereas the latter uses X-specific fonts and
     metrics.

`-N'
     Don't allow newlines with `eqn' delimiters.  This is the same as
     the `-N' option in `geqn'.

`-S'
     Safer mode.  Pass the `-S' option to `gpic' and disable the
     `open', `opena', `pso', `sy', and `pi' requests.  For security
     reasons, this is enabled by default.

`-U'
     Unsafe mode.  This enables the `open', `opena', `pso', `sy', and
     `pi' requests.

`-a'
     Generate an ASCII approximation of the typeset output.  The
     read-only register `.A' is then set to 1.  *Note Built-in
     Registers::.  A typical example is


          groff -a -man -Tdvi troff.man | less

     which shows how lines are broken for the DVI device.  Note that
     this option is rather useless today since graphic output devices
     are available virtually everywhere.

`-b'
     Print a backtrace with each warning or error message.  This
     backtrace should help track down the cause of the error.  The line
     numbers given in the backtrace may not always be correct: `gtroff'
     can get confused by `as' or `am' requests while counting line
     numbers.

`-i'
     Read the standard input after all the named input files have been
     processed.

`-wNAME'
     Enable warning NAME.  Available warnings are described in *Note
     Debugging::.  Multiple `-w' options are allowed.

`-WNAME'
     Inhibit warning NAME.  Multiple `-W' options are allowed.

`-E'
     Inhibit all error messages.

`-C'
     Enable compatibility mode.  *Note Implementation Differences::,
     for the list of incompatibilities between `groff' and AT&T `troff'.

`-dCS'
`-dNAME=S'
     Define C or NAME to be a string S.  C must be a one-letter name;
     NAME can be of arbitrary length.  All string assignments happen
     before loading any macro file (including the start-up file).

`-fFAM'
     Use FAM as the default font family.  *Note Font Families::.

`-mNAME'
     Read in the file `NAME.tmac'.  Normally `groff' searches for this
     in its macro directories.  If it isn't found, it tries `tmac.NAME'
     (searching in the same directories).

`-nNUM'
     Number the first page NUM.

`-oLIST'
     Output only pages in LIST, which is a comma-separated list of page
     ranges; `N' means print page N, `M-N' means print every page
     between M and N, `-N' means print every page up to N, `N-' means
     print every page beginning with N.  `gtroff' exits after printing
     the last page in the list.  All the ranges are inclusive on both
     ends.

     Within `gtroff', this information can be extracted with the `.P'
     register.  *Note Built-in Registers::.

     If your document restarts page numbering at the beginning of each
     chapter, then `gtroff' prints the specified page range for each
     chapter.

`-rCN'
`-rNAME=N'
     Set number register C or NAME to the value N.  C must be a
     one-letter name; NAME can be of arbitrary length.  N can be any
     `gtroff' numeric expression.  All register assignments happen
     before loading any macro file (including the start-up file).

`-FDIR'
     Search `DIR' for subdirectories `devNAME' (NAME is the name of the
     device), for the `DESC' file, and for font files before looking in
     the standard directories (*note Font Directories::).  This option
     is passed to all pre- and postprocessors using the
     `GROFF_FONT_PATH' environment variable.

`-MDIR'
     Search directory `DIR' for macro files before the standard
     directories (*note Macro Directories::).

`-IDIR'
     This option may be used to specify a directory to search for files.
     It is passed to the following programs:

        * `gsoelim' (see *Note gsoelim:: for more details); it also
          implies `groff''s `-s' option.

        * `gtroff'; it is used to search files named in the `psbb' and
          `so' requests.

        * `grops'; it is used to search files named in the
          `\X'ps: import' and `\X'ps: file' escapes.

     The current directory is always searched first. This option may be
     specified more than once; the directories will be searched in the
     order specified. No directory search is performed for files
     specified using an absolute path.


File: groff,  Node: Environment,  Next: Macro Directories,  Prev: Groff Options,  Up: Invoking groff

Environment
===========

There are also several environment variables (of the operating system,
not within `gtroff') which can modify the behavior of `groff'.

`GROFF_COMMAND_PREFIX'
     If this is set to X, then `groff' runs `Xtroff' instead of
     `gtroff'.  This also applies to `tbl', `pic', `eqn', `grn',
     `refer', and `soelim'.  It does not apply to `grops', `grodvi',
     `grotty', `pre-grohtml', `post-grohtml', `grolj4', and `gxditview'.

     The default command prefix is determined during the installation
     process.  If a non-GNU troff system is found, prefix `g' is used,
     none otherwise.

`GROFF_TMAC_PATH'
     A colon-separated list of directories in which to search for macro
     files (before the default directories are tried).  *Note Macro
     Directories::.

`GROFF_TYPESETTER'
     The default output device.

`GROFF_FONT_PATH'
     A colon-separated list of directories in which to search for the
     `dev'NAME directory (before the default directories are tried).
     *Note Font Directories::.

`GROFF_BIN_PATH'
     This search path, followed by `PATH', is used for commands executed
     by `groff'.

`GROFF_TMPDIR'
     The directory in which `groff' creates temporary files.  If this is
     not set and `TMPDIR' is set, temporary files are created in that
     directory.  Otherwise temporary files are created in a
     system-dependent default directory (on Unix and GNU/Linux systems,
     this is usually `/tmp').  `grops', `grefer', `pre-grohtml', and
     `post-grohtml' can create temporary files in this directory.

   Note that MS-DOS and MS-Windows ports of `groff' use semi-colons,
rather than colons, to separate the directories in the lists described
above.


File: groff,  Node: Macro Directories,  Next: Font Directories,  Prev: Environment,  Up: Invoking groff

Macro Directories
=================

All macro file names must be named `NAME.tmac' or `tmac.NAME' to make
the `-mNAME' command line option work.  The `mso' request doesn't have
this restriction; any file name can be used, and `gtroff' won't try to
append or prepend the `tmac' string.

   Macro files are kept in the "tmac directories", all of which
constitute the "tmac path".  The elements of the search path for macro
files are (in that order):

   * The directories specified with `gtroff''s or `groff''s `-M'
     command line option.

   * The directories given in the `GROFF_TMAC_PATH' environment
     variable.

   * The current directory (only if in unsafe mode using the `-U'
     command line switch).

   * The home directory.

   * A platform-dependent directory, a site-specific
     (platform-independent) directory, and the main tmac directory; the
     default locations are


          /usr/local/lib/groff/site-tmac
          /usr/local/share/groff/site-tmac
          /usr/local/share/groff/1.18.2/tmac

     assuming that the version of `groff' is 1.18.2, and the
     installation prefix was `/usr/local'.  It is possible to fine-tune
     those directories during the installation process.


File: groff,  Node: Font Directories,  Next: Paper Size,  Prev: Macro Directories,  Up: Invoking groff

Font Directories
================

Basically, there is no restriction how font files for `groff' are named
and how long font names are; however, to make the font family mechanism
work (*note Font Families::), fonts within a family should start with
the family name, followed by the shape.  For example, the Times family
uses `T' for the family name and `R', `B', `I', and `BI' to indicate
the shapes `roman', `bold', `italic', and `bold italic', respectively.
Thus the final font names are `TR', `TB', `TI', and `TBI'.

   All font files are kept in the "font directories" which constitute
the "font path".  The file search functions will always append the
directory `dev'NAME, where NAME is the name of the output device.
Assuming, say, DVI output, and `/foo/bar' as a font directory, the font
files for `grodvi' must be in `/foo/bar/devdvi'.

   The elements of the search path for font files are (in that order):

   * The directories specified with `gtroff''s or `groff''s `-F'
     command line option.  All device drivers and some preprocessors
     also have this option.

   * The directories given in the `GROFF_FONT_PATH' environment
     variable.

   * A site-specific directory and the main font directory; the default
     locations are


          /usr/local/share/groff/site-font
          /usr/local/share/groff/1.18.2/font

     assuming that the version of `groff' is 1.18.2, and the
     installation prefix was `/usr/local'.  It is possible to fine-tune
     those directories during the installation process.


File: groff,  Node: Paper Size,  Next: Invocation Examples,  Prev: Font Directories,  Up: Invoking groff

Paper Size
==========

In groff, the page size for `gtroff' and for output devices are handled
separately.  *Note Page Layout::, for vertical manipulation of the page
size.  *Note Line Layout::, for horizontal changes.

   A default paper size can be set in the device's `DESC' file.  Most
output devices also have a command line option `-p' to override the
default paper size and option `-l' to use landscape orientation.  *Note
DESC File Format::, for a description of the `papersize' keyword which
takes the same argument as `-p'.

   A convenient shorthand to set a particular paper size for `gtroff'
is command line option `-dpaper=SIZE'.  This defines string `paper'
which is processed in file `papersize.tmac' (loaded in the start-up
file `troffrc' by default).  Possible values for SIZE are the same as
the predefined values for the `papersize' keyword (but only in
lowercase) except `a7'-`d7'.  An appended `l' (ell) character denotes
landscape orientation.

   For example, use the following for PS output on A4 paper in landscape
orientation:


     groff -Tps -dpaper=a4l -P-pa4 -P-l -ms foo.ms > foo.ps

   Note that it is up to the particular macro package to respect default
page dimensions set in this way (most do).


File: groff,  Node: Invocation Examples,  Prev: Paper Size,  Up: Invoking groff

Invocation Examples
===================

This section lists several common uses of `groff' and the corresponding
command lines.


     groff file

This command processes `file' without a macro package or a
preprocessor.  The output device is the default, `ps', and the output
is sent to `stdout'.


     groff -t -mandoc -Tascii file | less

This is basically what a call to the `man' program does.  `gtroff'
processes the manual page `file' with the `mandoc' macro file (which in
turn either calls the `man' or the `mdoc' macro package), using the
`tbl' preprocessor and the ASCII output device.  Finally, the `less'
pager displays the result.


     groff -X -m me file

Preview `file' with `gxditview', using the `me' macro package.  Since
no `-T' option is specified, use the default device (`ps').  Note that
you can either say `-m me' or `-me'; the latter is an anachronism from
the early days of UNIX.(1) (*note Invocation Examples-Footnote-1::)


     groff -man -rD1 -z file

Check `file' with the `man' macro package, forcing double-sided
printing - don't produce any output.

* Menu:

* grog::


File: groff,  Node: Invocation Examples-Footnotes,  Up: Invocation Examples

   (1) The same is true for the other main macro packages that come
with `groff': `man', `mdoc', `ms', `mm', and `mandoc'.  This won't work
in general; for example, to load `trace.tmac', either `-mtrace' or
`-m trace' must be used.


File: groff,  Node: grog,  Prev: Invocation Examples,  Up: Invocation Examples

`grog'
------

`grog' reads files, guesses which of the `groff' preprocessors and/or
macro packages are required for formatting them, and prints the `groff'
command including those options on the standard output.  It generates
one or more of the options `-e', `-man', `-me', `-mm', `-mom', `-ms',
`-mdoc', `-mdoc-old', `-p', `-R', `-g', `-G', `-s', and `-t'.

   A special file name `-' refers to the standard input.  Specifying no
files also means to read the standard input.  Any specified options are
included in the printed command.  No space is allowed between options
and their arguments.  The only options recognized are `-C' (which is
also passed on) to enable compatibility mode, and `-v' to print the
version number and exit.

   For example,


     grog -Tdvi paper.ms

guesses the appropriate command to print `paper.ms' and then prints it
to the command line after adding the `-Tdvi' option.  For direct
execution, enclose the call to `grog' in backquotes at the UNIX shell
prompt:


     `grog -Tdvi paper.ms` > paper.dvi

As seen in the example, it is still necessary to redirect the output to
something meaningful (i.e. either a file or a pager program like
`less').


File: groff,  Node: Tutorial for Macro Users,  Next: Macro Packages,  Prev: Invoking groff,  Up: Top

Tutorial for Macro Users
************************

Most users tend to use a macro package to format their papers.  This
means that the whole breadth of `groff' is not necessary for most
people.  This chapter covers the material needed to efficiently use a
macro package.

* Menu:

* Basics::
* Common Features::


File: groff,  Node: Basics,  Next: Common Features,  Prev: Tutorial for Macro Users,  Up: Tutorial for Macro Users

Basics
======

This section covers some of the basic concepts necessary to understand
how to use a macro package.(1) (*note Basics-Footnote-1::) References
are made throughout to more detailed information, if desired.

   `gtroff' reads an input file prepared by the user and outputs a
formatted document suitable for publication or framing.  The input
consists of text, or words to be printed, and embedded commands
("requests" and "escapes"), which tell `gtroff' how to format the
output.  For more detail on this, see *Note Embedded Commands::.

   The word "argument" is used in this chapter to mean a word or number
which appears on the same line as a request, and which modifies the
meaning of that request.  For example, the request


     .sp

spaces one line, but


     .sp 4

spaces four lines.  The number 4 is an argument to the `sp' request
which says to space four lines instead of one.  Arguments are separated
from the request and from each other by spaces (_no_ tabs).  More
details on this can be found in *Note Request and Macro Arguments::.

   The primary function of `gtroff' is to collect words from input
lines, fill output lines with those words, justify the right-hand margin
by inserting extra spaces in the line, and output the result.  For
example, the input:


     Now is the time
     for all good men
     to come to the aid
     of their party.
     Four score and seven
     years ago, etc.

is read, packed onto output lines, and justified to produce:

     Now is the time for all good men to come to the aid of their party.
     Four score and seven years ago, etc.

   Sometimes a new output line should be started even though the current
line is not yet full; for example, at the end of a paragraph.  To do
this it is possible to cause a "break", which starts a new output line.
Some requests cause a break automatically, as normally do blank input
lines and input lines beginning with a space.

   Not all input lines are text to be formatted.  Some input lines are
requests which describe how to format the text.  Requests always have a
period (`.') or an apostrophe (`'') as the first character of the input
line.

   The text formatter also does more complex things, such as
automatically numbering pages, skipping over page boundaries, putting
footnotes in the correct place, and so forth.

   Here are a few hints for preparing text for input to `gtroff'.

   * First, keep the input lines short.  Short input lines are easier to
     edit, and `gtroff' packs words onto longer lines anyhow.

   * In keeping with this, it is helpful to begin a new line after every
     comma or phrase, since common corrections are to add or delete
     sentences or phrases.

   * End each sentence with two spaces - or better, start each sentence
     on a new line.  `gtroff' recognizes characters that usually end a
     sentence, and inserts sentence space accordingly.

   * Do not hyphenate words at the end of lines - `gtroff' is smart
     enough to hyphenate words as needed, but is not smart enough to
     take hyphens out and join a word back together.  Also, words such
     as "mother-in-law" should not be broken over a line, since then a
     space can occur where not wanted, such as "mother- in-law".

   `gtroff' double-spaces output text automatically if you use the
request `.ls 2'.  Reactivate single-spaced mode by typing `.ls 1'.(2)
(*note Basics-Footnote-2::)

   A number of requests allow to change the way the output looks,
sometimes called the "layout" of the output page.  Most of these
requests adjust the placing of "whitespace" (blank lines or spaces).

   The `bp' request starts a new page, causing a line break.

   The request `.sp N' leaves N lines of blank space.  N can be omitted
(meaning skip a single line) or can be of the form Ni (for N inches) or
Nc (for N centimeters).  For example, the input:


     .sp 1.5i
     My thoughts on the subject
     .sp

leaves one and a half inches of space, followed by the line "My
thoughts on the subject", followed by a single blank line (more
measurement units are available, see *Note Measurements::).

   Text lines can be centered by using the `ce' request.  The line
after `ce' is centered (horizontally) on the page.  To center more than
one line, use `.ce N' (where N is the number of lines to center),
followed by the N lines.  To center many lines without counting them,
type:


     .ce 1000
     lines to center
     .ce 0

The `.ce 0' request tells `groff' to center zero more lines, in other
words, stop centering.

   All of these requests cause a break; that is, they always start a new
line.  To start a new line without performing any other action, use
`br'.


File: groff,  Node: Basics-Footnotes,  Up: Basics

   (1) This section is derived from `Writing Papers with nroff using
-me' by Eric P. Allman.

   (2) If you need finer granularity of the vertical space, use the
`pvs' request (*note Changing Type Sizes::).


File: groff,  Node: Common Features,  Prev: Basics,  Up: Tutorial for Macro Users

Common Features
===============

`gtroff' provides very low-level operations for formatting a document.
There are many common routine operations which are done in all
documents.  These common operations are written into "macros" and
collected into a "macro package".

   All macro packages provide certain common capabilities which fall
into the following categories.

* Menu:

* Paragraphs::
* Sections and Chapters::
* Headers and Footers::
* Page Layout Adjustment::
* Displays::
* Footnotes and Annotations::
* Table of Contents::
* Indices::
* Paper Formats::
* Multiple Columns::
* Font and Size Changes::
* Predefined Strings::
* Preprocessor Support::
* Configuration and Customization::


File: groff,  Node: Paragraphs,  Next: Sections and Chapters,  Prev: Common Features,  Up: Common Features

Paragraphs
----------

One of the most common and most used capability is starting a
paragraph.  There are a number of different types of paragraphs, any of
which can be initiated with macros supplied by the macro package.
Normally, paragraphs start with a blank line and the first line
indented, like the text in this manual.  There are also block style
paragraphs, which omit the indentation:


     Some   men  look   at  constitutions   with  sanctimonious
     reverence, and deem them like the ark of the covenant, too
     sacred to be touched.

And there are also indented paragraphs which begin with a tag or label
at the margin and the remaining text indented.


     one   This is  the first paragraph.  Notice  how the first
           line of  the resulting  paragraph lines up  with the
           other lines in the paragraph.


     longlabel
           This  paragraph   had  a  long   label.   The  first
           character of text on the first line does not line up
           with  the  text  on  second  and  subsequent  lines,
           although they line up with each other.

   A variation of this is a bulleted list.


     .     Bulleted lists start with a bullet.   It is possible
           to use other glyphs instead of the bullet.  In nroff
           mode using the ASCII character set for output, a dot
           is used instead of a real bullet.


File: groff,  Node: Sections and Chapters,  Next: Headers and Footers,  Prev: Paragraphs,  Up: Common Features

Sections and Chapters
---------------------

Most macro packages supply some form of section headers.  The simplest
kind is simply the heading on a line by itself in bold type.  Others
supply automatically numbered section heading or different heading
styles at different levels.  Some, more sophisticated, macro packages
supply macros for starting chapters and appendices.


File: groff,  Node: Headers and Footers,  Next: Page Layout Adjustment,  Prev: Sections and Chapters,  Up: Common Features

Headers and Footers
-------------------

Every macro package gives some way to manipulate the "headers" and
"footers" (also called "titles") on each page.  This is text put at the
top and bottom of each page, respectively, which contain data like the
current page number, the current chapter title, and so on.  Its
appearance is not affected by the running text.  Some packages allow
for different ones on the even and odd pages (for material printed in a
book form).

   The titles are called "three-part titles", that is, there is a
left-justified part, a centered part, and a right-justified part.  An
automatically generated page number may be put in any of these fields
with the `%' character (see *Note Page Layout::, for more details).


File: groff,  Node: Page Layout Adjustment,  Next: Displays,  Prev: Headers and Footers,  Up: Common Features

Page Layout
-----------

Most macro packages let the user specify top and bottom margins and
other details about the appearance of the printed pages.


File: groff,  Node: Displays,  Next: Footnotes and Annotations,  Prev: Page Layout Adjustment,  Up: Common Features

Displays
--------

"Displays" are sections of text to be set off from the body of the
paper.  Major quotes, tables, and figures are types of displays, as are
all the examples used in this document.

   "Major quotes" are quotes which are several lines long, and hence
are set in from the rest of the text without quote marks around them.

   A "list" is an indented, single-spaced, unfilled display.  Lists
should be used when the material to be printed should not be filled and
justified like normal text, such as columns of figures or the examples
used in this paper.

   A "keep" is a display of lines which are kept on a single page if
possible.  An example for a keep might be a diagram.  Keeps differ from
lists in that lists may be broken over a page boundary whereas keeps are
not.

   "Floating keeps" move relative to the text.  Hence, they are good for
things which are referred to by name, such as "See figure 3".  A
floating keep appears at the bottom of the current page if it fits;
otherwise, it appears at the top of the next page.  Meanwhile, the
surrounding text `flows' around the keep, thus leaving no blank areas.


File: groff,  Node: Footnotes and Annotations,  Next: Table of Contents,  Prev: Displays,  Up: Common Features

Footnotes and Annotations
-------------------------

There are a number of requests to save text for later printing.

   "Footnotes" are printed at the bottom of the current page.

   "Delayed text" is very similar to a footnote except that it is
printed when called for explicitly.  This allows a list of references to
appear (for example) at the end of each chapter, as is the convention in
some disciplines.

   Most macro packages which supply this functionality also supply a
means of automatically numbering either type of annotation.


File: groff,  Node: Table of Contents,  Next: Indices,  Prev: Footnotes and Annotations,  Up: Common Features

Table of Contents
-----------------

"Tables of contents" are a type of delayed text having a tag (usually
the page number) attached to each entry after a row of dots.  The table
accumulates throughout the paper until printed, usually after the paper
has ended.  Many macro packages provide the ability to have several
tables of contents (e.g. a standard table of contents, a list of
tables, etc).


File: groff,  Node: Indices,  Next: Paper Formats,  Prev: Table of Contents,  Up: Common Features

Indices
-------

While some macro packages use the term "index", none actually provide
that functionality.  The facilities they call indices are actually more
appropriate for tables of contents.

   To produce a real index in a document, external tools like the
`makeindex' program are necessary.


File: groff,  Node: Paper Formats,  Next: Multiple Columns,  Prev: Indices,  Up: Common Features

Paper Formats
-------------

Some macro packages provide stock formats for various kinds of
documents.  Many of them provide a common format for the title and
opening pages of a technical paper.  The `mm' macros in particular
provide formats for letters and memoranda.


File: groff,  Node: Multiple Columns,  Next: Font and Size Changes,  Prev: Paper Formats,  Up: Common Features

Multiple Columns
----------------

Some macro packages (but not `man') provide the ability to have two or
more columns on a page.


File: groff,  Node: Font and Size Changes,  Next: Predefined Strings,  Prev: Multiple Columns,  Up: Common Features

Font and Size Changes
---------------------

The built-in font and size functions are not always intuitive, so all
macro packages provide macros to make these operations simpler.


File: groff,  Node: Predefined Strings,  Next: Preprocessor Support,  Prev: Font and Size Changes,  Up: Common Features

Predefined Strings
------------------

Most macro packages provide various predefined strings for a variety of
uses; examples are sub- and superscripts, printable dates, quotes and
various special characters.


File: groff,  Node: Preprocessor Support,  Next: Configuration and Customization,  Prev: Predefined Strings,  Up: Common Features

Preprocessor Support
--------------------

All macro packages provide support for various preprocessors and may
extend their functionality.

   For example, all macro packages mark tables (which are processed with
`gtbl') by placing them between `TS' and `TE' macros.  The `ms' macro
package has an option, `.TS H', that prints a caption at the top of a
new page (when the table is too long to fit on a single page).


File: groff,  Node: Configuration and Customization,  Prev: Preprocessor Support,  Up: Common Features

Configuration and Customization
-------------------------------

Some macro packages provide means of customizing many of the details of
how the package behaves.  This ranges from setting the default type size
to changing the appearance of section headers.


File: groff,  Node: Macro Packages,  Next: gtroff Reference,  Prev: Tutorial for Macro Users,  Up: Top

Macro Packages
**************

This chapter documents the main macro packages that come with `groff'.

   Different main macro packages can't be used at the same time; for
example


     groff -m man foo.man -m ms bar.doc

doesn't work.  Note that option arguments are processed before
non-option arguments; the above (failing) sample is thus reordered to


     groff -m man -m ms foo.man bar.doc

* Menu:

* man::
* mdoc::
* ms::
* me::
* mm::


File: groff,  Node: man,  Next: mdoc,  Prev: Macro Packages,  Up: Macro Packages

`man'
=====

This is the most popular and probably the most important macro package
of `groff'.  It is easy to use, and a vast majority of manual pages are
based on it.

* Menu:

* Man options::
* Man usage::
* Man font macros::
* Miscellaneous man macros::
* Predefined man strings::
* Preprocessors in man pages::
* Optional man extensions::


File: groff,  Node: Man options,  Next: Man usage,  Prev: man,  Up: man

Options
-------

The command line format for using the `man' macros with `groff' is:


     groff -m man [ -rLL=LENGTH ] [ -rLT=LENGTH ] [ -rFT=DIST ]
           [ -rcR=1 ] [ -rC1 ] [ -rD1 ] [-rHY=FLAGS ]
           [ -rPNNN ] [ -rSXX ] [ -rXNNN ]
           [ -rIN=LENGTH ] [ -rSN=LENGTH ] [ FILES... ]

It is possible to use `-man' instead of `-m man'.

`-rcR=1'
     This option (the default if a TTY output device is used) creates a
     single, very long page instead of multiple pages.  Use `-rcR=0' to
     disable it.

`-rC1'
     If more than one manual page is given on the command line, number
     the pages continuously, rather than starting each at 1.

`-rD1'
     Double-sided printing.  Footers for even and odd pages are
     formatted differently.

`-rFT=DIST'
     Set the position of the footer text to DIST.  If positive, the
     distance is measured relative to the top of the page, otherwise it
     is relative to the bottom.  The default is -0.5i.

`-rHY=FLAGS'
     Set hyphenation flags.  Possible values are 1 to hyphenate without
     restrictions, 2  to not hyphenate the last word on a page, 4 to
     not hyphenate the last two characters of a word, and 8 to not
     hyphenate the first two characters of a word.  These values are
     additive; the default is 14.

`-rIN=LENGTH'
     Set the body text indent to LENGTH.  If not specified, the indent
     defaults to 7n (7 characters) in nroff mode and 7.2n otherwise.
     For nroff, this value should always be an integer multiple of unit
     `n' to get consistent indentation.

`-rLL=LENGTH'
     Set line length to LENGTH.  If not specified, the line length
     defaults to 78 en in nroff mode (this is 78 characters per line)
     and 6.5 inch otherwise.

`-rLT=LENGTH'
     Set title length to LENGTH.  If not specified, the title length
     defaults to the line length.

`-rPNNN'
     Page numbering starts with NNN rather than with 1.

`-rSXX'
     Use XX (which can be 10, 11, or 12pt) as the base document font
     size instead of the default value of 10pt.

`-rSN=LENGTH'
     Set the indent for sub-subheadings to LENGTH.  If not specified,
     the indent defaults to 3n.

`-rXNNN'
     After page NNN, number pages as NNNa, NNNb, NNNc, etc.  For
     example, the option `-rX2' produces the following page numbers: 1,
     2, 2a, 2b, 2c, etc.


File: groff,  Node: Man usage,  Next: Man font macros,  Prev: Man options,  Up: man

Usage
-----

This section describes the available macros for manual pages.  For
further customization, put additional macros and requests into the file
`man.local' which is loaded immediately after the `man' package.

 - Macro: .TH title section [extra1 [extra2 [extra3]]]
     Set the title of the man page to TITLE and the section to SECTION,
     which must have a value between 1 and 8.  The value of SECTION may
     also have a string appended, e.g. `.pm', to indicate a specific
     subsection of the man pages.

     Both TITLE and SECTION are positioned at the left and right in the
     header line (with SECTION in parentheses immediately appended to
     TITLE.  EXTRA1 is positioned in the middle of the footer line.
     EXTRA2 is positioned at the left in the footer line (or at the
     left on even pages and at the right on odd pages if double-sided
     printing is active).  EXTRA3 is centered in the header line.

     For HTML output, headers and footers are completely suppressed.

     Additionally, this macro starts a new page; the new line number
     is 1 again (except if the `-rC1' option is given on the command
     line) - this feature is intended only for formatting multiple man
     pages; a single man page should contain exactly one `TH' macro at
     the beginning of the file.

 - Macro: .SH [heading]
     Set up an unnumbered section heading sticking out to the left.
     Prints out all the text following `SH' up to the end of the line
     (or the text in the next line if there is no argument to `SH') in
     bold face (or the font specified by the string `HF'), one size
     larger than the base document size.  Additionally, the left margin
     and the indentation for the following text is reset to its default
     value.

 - Macro: .SS [heading]
     Set up an unnumbered (sub)section heading.  Prints out all the text
     following `SS' up to the end of the line (or the text in the next
     line if there is no argument to `SS') in bold face (or the font
     specified by the string `HF'), at the same size as the base
     document size.  Additionally, the left margin and the indentation
     for the following text is reset to its default value.

 - Macro: .TP [nnn]
     Set up an indented paragraph with label.  The indentation is set to
     NNN if that argument is supplied (the default unit is `n' if
     omitted), otherwise it is set to the previous indentation value
     specified with `TP', `IP', or `HP' (or to the default value if
     none of them have been used yet).

     The first line of text following this macro is interpreted as a
     string to be printed flush-left, as it is appropriate for a label.
     It is not interpreted as part of a paragraph, so there is no
     attempt to fill the first line with text from the following input
     lines.  Nevertheless, if the label is not as wide as the
     indentation the paragraph starts at the same line (but indented),
     continuing on the following lines.  If the label is wider than the
     indentation the descriptive part of the paragraph begins on the
     line following the label, entirely indented.  Note that neither
     font shape nor font size of the label is set to a default value;
     on the other hand, the rest of the text has default font settings.

 - Macro: .LP
 - Macro: .PP
 - Macro: .P
     These macros are mutual aliases.  Any of them causes a line break
     at the current position, followed by a vertical space downwards by
     the amount specified by the `PD' macro.  The font size and shape
     are reset to the default value (10pt roman if no `-rS' option is
     given on the command line).  Finally, the current left margin and
     the indentation is restored.

 - Macro: .IP [designator [nnn]]
     Set up an indented paragraph, using DESIGNATOR as a tag to mark
     its beginning.  The indentation is set to NNN if that argument is
     supplied (default unit is `n'), otherwise it is set to the
     previous indentation value specified with `TP', `IP', or `HP' (or
     the default value if none of them have been used yet).  Font size
     and face of the paragraph (but not the designator) are reset to
     their default values.

     To start an indented paragraph with a particular indentation but
     without a designator, use `""' (two double quotes) as the first
     argument of `IP'.

     For example, to start a paragraph with bullets as the designator
     and 4 en indentation, write


          .IP \(bu 4


 - Macro: .HP [nnn]
     Set up a paragraph with hanging left indentation.  The indentation
     is set to NNN if that argument is supplied (default unit is `n'),
     otherwise it is set to the previous indentation value specified
     with `TP', `IP', or `HP' (or the default value if non of them have
     been used yet).  Font size and face are reset to their default
     values.

 - Macro: .RS [nnn]
     Move the left margin to the right by the value NNN if specified
     (default unit is `n'); otherwise it is set to the previous
     indentation value specified with `TP', `IP', or `HP' (or to the
     default value if none of them have been used yet).  The
     indentation value is then set to the default.

     Calls to the `RS' macro can be nested.

 - Macro: .RE [nnn]
     Move the left margin back to level NNN, restoring the previous left
     margin.  If no argument is given, it moves one level back.  The
     first level (i.e., no call to `RS' yet) has number 1, and each call
     to `RS' increases the level by 1.

   To summarize, the following macros cause a line break with the
insertion of vertical space (which amount can be changed with the `PD'
macro): `SH', `SS', `TP', `LP' (`PP', `P'), `IP', and `HP'.

   The macros `RS' and `RE' also cause a break but do not insert
vertical space.

   Finally, the macros `SH', `SS', `LP' (`PP', `P'), and `RS' reset the
indentation to its default value.


File: groff,  Node: Man font macros,  Next: Miscellaneous man macros,  Prev: Man usage,  Up: man

Macros to set fonts
-------------------

The standard font is roman; the default text size is 10 point.  If
command line option `-rS=N' is given, use Npt as the default text size.

 - Macro: .SM [text]
     Set the text on the same line or the text on the next line in a
     font that is one point size smaller than the default font.

 - Macro: .SB [text]
     Set the text on the same line or the text on the next line in bold
     face font, one point size smaller than the default font.

 - Macro: .BI text
     Set its arguments alternately in bold face and italic, without a
     space between the arguments.  Thus,


          .BI this "word and" that

     produces "thisword andthat" with "this" and "that" in bold face,
     and "word and" in italics.

 - Macro: .IB text
     Set its arguments alternately in italic and bold face, without a
     space between the arguments.

 - Macro: .RI text
     Set its arguments alternately in roman and italic, without a space
     between the arguments.

 - Macro: .IR text
     Set its arguments alternately in italic and roman, without a space
     between the arguments.

 - Macro: .BR text
     Set its arguments alternately in bold face and roman, without a
     space between the arguments.

 - Macro: .RB text
     Set its arguments alternately in roman and bold face, without a
     space between the arguments.

 - Macro: .B [text]
     Set TEXT in bold face.  If no text is present on the line where
     the macro is called, then the text of the next line appears in bold
     face.

 - Macro: .I [text]
     Set TEXT in italic.  If no text is present on the line where the
     macro is called, then the text of the next line appears in italic.


File: groff,  Node: Miscellaneous man macros,  Next: Predefined man strings,  Prev: Man font macros,  Up: man

Miscellaneous macros
--------------------

The default indentation is 7.2n in troff mode and 7n in nroff mode
except for `grohtml' which ignores indentation.

 - Macro: .DT
     Set tabs every 0.5 inches.  Since this macro is always executed
     during a call to the `TH' macro, it makes sense to call it only if
     the tab positions have been changed.

 - Macro: .PD [nnn]
     Adjust the empty space before a new paragraph (or section).  The
     optional argument gives the amount of space (default unit is `v');
     without parameter, the value is reset to its default value (1 line
     in nroff mode, 0.4v otherwise).

     This affects the macros `SH', `SS', `TP', `LP' (as well as `PP'
     and `P'), `IP', and `HP'.

   The following two macros are included for BSD compatibility.

 - Macro: .AT [system [release]]
     Alter the footer for use with AT&T manpages.  This command exists
     only for compatibility; don't use it.  The first argument SYSTEM
     can be:

    `3'
          7th Edition (the default)

    `4'
          System III

    `5'
          System V

     An optional second argument RELEASE to `AT' specifies the release
     number (such as "System V Release 3").

 - Macro: .UC [version]
     Alters the footer for use with BSD manpages.  This command exists
     only for compatibility; don't use it.  The argument can be:

    `3'
          3rd Berkeley Distribution (the default)

    `4'
          4th Berkeley Distribution

    `5'
          4.2 Berkeley Distribution

    `6'
          4.3 Berkeley Distribution

    `7'
          4.4 Berkeley Distribution


File: groff,  Node: Predefined man strings,  Next: Preprocessors in man pages,  Prev: Miscellaneous man macros,  Up: man

Predefined strings
------------------

The following strings are defined:

 - String: \*[S]
     Switch back to the default font size.

 - String: \*[HF]
     The typeface used for headings.  The default is `B'.

 - String: \*[R]
     The `registered' sign.

 - String: \*[Tm]
     The `trademark' sign.

 - String: \*[lq]
 - String: \*[rq]
     Left and right quote.  This is equal to `\(lq' and `\(rq',
     respectively.


File: groff,  Node: Preprocessors in man pages,  Next: Optional man extensions,  Prev: Predefined man strings,  Up: man

Preprocessors in `man' pages
----------------------------

If a preprocessor like `gtbl' or `geqn' is needed, it has become common
usage to make the first line of the man page look like this:


     '\" WORD

Note the single space character after the double quote.  WORD consists
of letters for the needed preprocessors: `e' for `geqn', `r' for
`grefer', `t' for `gtbl'.  Modern implementations of the `man' program
read this first line and automatically call the right preprocessor(s).


File: groff,  Node: Optional man extensions,  Prev: Preprocessors in man pages,  Up: man

Optional `man' extensions
-------------------------

Use the file `man.local' for local extensions to the `man' macros or
for style changes.

Custom headers and footers
..........................

In groff versions 1.18.2 and later, you can specify custom headers and
footers by redefining the following macros in `man.local'.

 - Macro: .PT
     Control the content of the headers.  Normally, the header prints
     the command name and section number on either side, and the
     optional fifth argument to `TH' in the center.

 - Macro: .BT
     Control the content of the footers.  Normally, the footer prints
     the page number and the third and fourth arguments to `TH'.

     Use the `FT' number register to specify the footer position.  The
     default is -0.5i.

Ultrix-specific man macros
..........................

The `groff' source distribution includes a file named `man.ultrix',
containing macros compatible with the Ultrix variant of `man'.  Copy
this file into `man.local' (or use the `mso' request to load it) to
enable the following macros.

 - Macro: .CT key
     Print `<CTRL/KEY>'.

 - Macro: .CW
     Print subsequent text using the constant width (Courier) typeface.

 - Macro: .Ds
     Begin a non-filled display.

 - Macro: .De
     End a non-filled display started with `Ds'.

 - Macro: .EX [indent]
     Begins a non-filled display using the constant width (Courier)
     typeface.  Use the optional INDENT argument to indent the display.

 - Macro: .EE
     End a non-filled display started with `EX'.

 - Macro: .G [text]
     Sets TEXT in Helvetica.  If no text is present on the line where
     the macro is called, then the text of the next line appears in
     Helvetica.

 - Macro: .GL [text]
     Sets TEXT in Helvetica Oblique.  If no text is present on the line
     where the macro is called, then the text of the next line appears
     in Helvetica Oblique.

 - Macro: .HB [text]
     Sets TEXT in Helvetica Bold.  If no text is present on the line
     where the macro is called, then all text up to the next `HB'
     appears in Helvetica Bold.

 - Macro: .TB [text]
     Identical to `HB'.

 - Macro: .MS title sect [punct]
     Set a manpage reference in Ultrix format.  The TITLE is in Courier
     instead of italic.  Optional punctuation follows the section
     number without an intervening space.

 - Macro: .NT [`C'] [title]
     Begin a note.  Print the optional title, or the word "Note",
     centered on the page.  Text following the macro makes up the body
     of the note, and is indented on both sides.  If the first argument
     is `C', the body of the note is printed centered (the second
     argument replaces the word "Note" if specified).

 - Macro: .NE
     End a note begun with `NT'.

 - Macro: .PN path [punct]
     Set the path name in constant width (Courier), followed by
     optional punctuation.

 - Macro: .Pn [punct] path [punct]
     When called with two arguments, identical to `PN'.  When called
     with three arguments, set the second argument in constant width
     (Courier), bracketed by the first and third arguments in the
     current font.

 - Macro: .R
     Switch to roman font and turn off any underlining in effect.

 - Macro: .RN
     Print the string `<RETURN>'.

 - Macro: .VS [`4']
     Start printing a change bar in the margin if the number `4' is
     specified.  Otherwise, this macro does nothing.

 - Macro: .VE
     End printing the change bar begun by `VS'.

Simple example
..............

The following example `man.local' file alters the `SH' macro to add
some extra vertical space before printing the heading.  Headings are
printed in Helvetica Bold.


     .\" Make the heading fonts Helvetica
     .ds HF HB
     .
     .\" Put more whitespace in front of headings.
     .rn SH SH-orig
     .de SH
     .  if t .sp (u;\\n[PD]*2)
     .  SH-orig \\$*
     ..


File: groff,  Node: mdoc,  Next: ms,  Prev: man,  Up: Macro Packages

`mdoc'
======

See the `groff_mdoc(7)' man page (type `man groff_mdoc' at the command
line).


File: groff,  Node: ms,  Next: me,  Prev: mdoc,  Up: Macro Packages

`ms'
====

The `-ms' macros are suitable for reports, letters, books, user
manuals, and so forth.  The package provides macros for cover pages,
section headings, paragraphs, lists, footnotes, pagination, and a table
of contents.

* Menu:

* ms Intro::
* General ms Structure::
* ms Document Control Registers::
* ms Cover Page Macros::
* ms Body Text::
* ms Page Layout::
* Differences from AT&T ms::


File: groff,  Node: ms Intro,  Next: General ms Structure,  Prev: ms,  Up: ms

Introduction to `ms'
--------------------

The original `-ms' macros were included with AT&T `troff' as well as the
`man' macros.  While the `man' package is intended for brief documents
that can be read on-line as well as printed, the `ms' macros are
suitable for longer documents that are meant to be printed rather than
read on-line.

   The `ms' macro package included with `groff' is a complete,
bottom-up re-implementation.  Several macros (specific to AT&T or
Berkeley) are not included, while several new commands are.  *Note
Differences from AT&T ms::, for more information.


File: groff,  Node: General ms Structure,  Next: ms Document Control Registers,  Prev: ms Intro,  Up: ms

General structure of an `ms' document
-------------------------------------

The `ms' macro package expects a certain amount of structure, but not
as much as packages such as `man' or `mdoc'.

   The simplest documents can begin with a paragraph macro (such as
`LP' or `PP'), and consist of text separated by paragraph macros or
even blank lines.  Longer documents have a structure as follows:

*Document type*
     If you invoke the `RP' (report) macro on the first line of the
     document, `groff' prints the cover page information on its own
     page; otherwise it prints the information on the first page with
     your document text immediately following.  Other document formats
     found in AT&T `troff' are specific to AT&T or Berkeley, and are
     not supported in `groff'.

*Format and layout*
     By setting number registers, you can change your document's type
     (font and size), margins, spacing, headers and footers, and
     footnotes.  *Note ms Document Control Registers::, for more
     details.

*Cover page*
     A cover page consists of a title, the author's name and
     institution, an abstract, and the date.  (1) (*note General ms
     Structure-Footnote-1::) *Note ms Cover Page Macros::, for more
     details.

*Body*
     Following the cover page is your document.  You can use the `ms'
     macros to write reports, letters, books, and so forth.  The
     package is designed for structured documents, consisting of
     paragraphs interspersed with headings and augmented by lists,
     footnotes, tables, and other common constructs.  *Note ms Body
     Text::, for more details.

*Table of contents*
     Longer documents usually include a table of contents, which you
     can invoke by placing the `TC' macro at the end of your document.
     The `ms' macros have minimal indexing facilities, consisting of the
     `IX' macro, which prints an entry on standard error.  Printing the
     table of contents at the end is necessary since `groff' is a
     single-pass text formatter, thus it cannot determine the page
     number of each section until that section has actually been set
     and printed.  Since `ms' output is intended for hardcopy, you can
     manually relocate the pages containing the table of contents
     between the cover page and the body text after printing.


File: groff,  Node: General ms Structure-Footnotes,  Up: General ms Structure

   (1) Actually, only the title is required.


File: groff,  Node: ms Document Control Registers,  Next: ms Cover Page Macros,  Prev: General ms Structure,  Up: ms

Document control registers
--------------------------

The following is a list of document control number registers.  For the
sake of consistency, set registers related to margins at the beginning
of your document, or just after the `RP' macro.  You can set other
registers later in your document, but you should keep them together at
the beginning to make them easy to find and edit as necessary.

Margin Settings
...............

 - Register: \n[PO]
     Defines the page offset (i.e. the left margin).  There is no
     explicit right margin setting; the combination of the `PO' and
     `LL' registers implicitly define the right margin width.

     Effective: next page.

     Default value: 1i.

 - Register: \n[LL]
     Defines the line length (i.e. the width of the body text).

     Effective: next paragraph.

     Default: 6i.

 - Register: \n[LT]
     Defines the title length (i.e. the header and footer width).  This
     is usually the same as `LL', but not necessarily.

     Effective: next paragraph.

     Default: 6i.

 - Register: \n[HM]
     Defines the header margin height at the top of the page.

     Effective: next page.

     Default: 1i.

 - Register: \n[FM]
     Defines the footer margin height at the bottom of the page.

     Effective: next page.

     Default: 1i.

Text Settings
.............

 - Register: \n[PS]
     Defines the point size of the body text.

     Effective: next paragraph.

     Default: 10p.

 - Register: \n[VS]
     Defines the space between lines (line height plus leading).

     Effective: next paragraph.

     Default: 12p.

Paragraph Settings
..................

 - Register: \n[PI]
     Defines the initial indent of a `.PP' paragraph.

     Effective: next paragraph.

     Default: 5n.

 - Register: \n[PD]
     Defines the space between paragraphs.

     Effective: next paragraph.

     Default: 0.3v.

 - Register: \n[QI]
     Defines the indent on both sides of a quoted (`.QP') paragraph.

     Effective: next paragraph.

     Default: 5n.

Footnote Settings
.................

 - Register: \n[FL]
     Defines the length of a footnote.

     Effective: next footnote.

     Default: `\n[LL]' * 5 / 6.

 - Register: \n[FI]
     Defines the footnote indent.

     Effective: next footnote.

     Default: 2n.

 - Register: \n[FF]
     The footnote format:
    `0'
          Prints the footnote number as a superscript; indents the
          footnote (default).

    `1'
          Prints the number followed by a period (like 1.)  and indents
          the footnote.

    `2'
          Like 1, without an indent.

    `3'
          Like 1, but prints the footnote number as a hanging paragraph.

     Effective: next footnote.

     Default: 0.

 - Register: \n[FPS]
     Defines the footnote point size.

     Effective: next footnote.

     Default: `\n[PS]' - 2.

 - Register: \n[FVS]
     Defines the footnote vertical spacing.

     Effective: next footnote.

     Default: `\n[FPS]' + 2.

 - Register: \n[FPD]
     Defines the footnote paragraph spacing.

     Effective: next footnote.

     Default: `\n[PD]' / 2.

Miscellaneous Number Registers
..............................

 - Register: \n[MINGW]
     Defines the minimum width between columns in a multi-column
     document.

     Effective: next page.

     Default: 2n.


File: groff,  Node: ms Cover Page Macros,  Next: ms Body Text,  Prev: ms Document Control Registers,  Up: ms

Cover page macros
-----------------

Use the following macros to create a cover page for your document in
the order shown.

 - Macro: .RP [`no']
     Specifies the report format for your document.  The report format
     creates a separate cover page.  The default action (no `.RP'
     macro) is to print a subset of the cover page on page 1 of your
     document.

     If you use the word `no' as an optional argument, `groff' prints a
     title page but does not repeat any of the title page information
     (title, author, abstract, etc.)  on page 1 of the document.

 - Macro: .DA [...]
     (optional) Print the current date, or the arguments to the macro
     if any, on the title page (if specified) and in the footers.  This
     is the default for `nroff'.

 - Macro: .ND [...]
     (optional) Print the current date, or the arguments to the macro
     if any, on the title page (if specified) but not in the footers.
     This is the default for `troff'.

 - Macro: .TL
     Specifies the document title.  `groff' collects text following the
     `.TL' macro into the title, until reaching the author name or
     abstract.

 - Macro: .AU
     Specifies the author's name, which appears on the line (or lines)
     immediately following.  You can specify multiple authors as
     follows:


          .AU
          John Doe
          .AI
          University of West Bumblefuzz
          .AU
          Martha Buck
          .AI
          Monolithic Corporation
          
          ...


 - Macro: .AI
     Specifies the author's institution.  You can specify multiple
     institutions in the same way that you specify multiple authors.

 - Macro: .AB [`no']
     Begins the abstract.  The default is to print the word ABSTRACT,
     centered and in italics, above the text of the abstract.  The word
     `no' as an optional argument suppresses this heading.

 - Macro: .AE
     End the abstract.

   The following is example mark-up for a title page.


     .RP
     .TL
     The Inevitability of Code Bloat
     in Commercial and Free Software
     .AU
     J. Random Luser
     .AI
     University of West Bumblefuzz
     .AB
     This report examines the long-term growth
     of the code bases in two large, popular software
     packages; the free Emacs and the commercial
     Microsoft Word.
     While differences appear in the type or order
     of features added, due to the different
     methodologies used, the results are the same
     in the end.
     .PP
     The free software approach is shown to be
     superior in that while free software can
     become as bloated as commercial offerings,
     free software tends to have fewer serious
     bugs and the added features are in line with
     user demand.
     .AE
     
     ... the rest of the paper follows ...


File: groff,  Node: ms Body Text,  Next: ms Page Layout,  Prev: ms Cover Page Macros,  Up: ms

Body text
---------

This section describes macros used to mark up the body of your document.
Examples include paragraphs, sections, and other groups.

* Menu:

* Paragraphs in ms::
* Headings in ms::
* Highlighting in ms::
* Lists in ms::
* Indents in ms::
* Tabstops in ms::
* ms Displays and Keeps::
* ms Insertions::
* Example multi-page table::
* ms Footnotes::


File: groff,  Node: Paragraphs in ms,  Next: Headings in ms,  Prev: ms Body Text,  Up: ms Body Text

Paragraphs
..........

The following paragraph types are available.

 - Macro: .PP
     Sets a paragraph with an initial indent.

 - Macro: .LP
     Sets a paragraph with no initial indent.

 - Macro: .QP
     Sets a paragraph that is indented at both left and right margins.
     The effect is identical to the HTML `<BLOCKQUOTE>' element.  The
     next paragraph or heading returns margins to normal.

 - Macro: .XP
     Sets a paragraph whose lines are indented, except for the first
     line.  This is a Berkeley extension.

   The following markup uses all four paragraph macros.


     .NH 2
     Cases used in the study
     .LP
     The following software and versions were
     considered for this report.
     .PP
     For commercial software, we chose
     .B "Microsoft Word for Windows" ,
     starting with version 1.0 through the
     current version (Word 2000).
     .PP
     For free software, we chose
     .B Emacs ,
     from its first appearance as a standalone
     editor through the current version (v20).
     See [Bloggs 2002] for details.
     .QP
     Franklin's Law applied to software:
     software expands to outgrow both
     RAM and disk space over time.
     .LP
     Bibliography:
     .XP
     Bloggs, Joseph R.,
     .I "Everyone's a Critic" ,
     Underground Press, March 2002.
     A definitive work that answers all questions
     and criticisms about the quality and usability of
     free software.


File: groff,  Node: Headings in ms,  Next: Highlighting in ms,  Prev: Paragraphs in ms,  Up: ms Body Text

Headings
........

Use headings to create a hierarchical structure for your document.  The
`ms' macros print headings in *bold*, using the same font family and
point size as the body text.

   The following describes the heading macros:

 - Macro: .NH curr-level
 - Macro: .NH S level0 ...
     Numbered heading.  The argument is either a numeric argument to
     indicate the level of the heading, or the letter `S' followed by
     numeric arguments to set the heading level explicitly.

     If you specify heading levels out of sequence, such as invoking
     `.NH 3' after `.NH 1', `groff' prints a warning on standard error.

 - Macro: .SH
     Unnumbered subheading.


File: groff,  Node: Highlighting in ms,  Next: Lists in ms,  Prev: Headings in ms,  Up: ms Body Text

Highlighting
............

The `ms' macros provide a variety of methods to highlight or emphasize
text:

 - Macro: .B [txt [post [pre]]]
     Sets its first argument in *bold type*.  If you specify a second
     argument, `groff' prints it in the previous font after the bold
     text, with no intervening space (this allows you to set
     punctuation after the highlighted text without highlighting the
     punctuation).  Similarly, it prints the third argument (if any) in
     the previous font *before* the first argument.  For example,


          .B foo ) (

     prints (*foo*).

     If you give this macro no arguments, `groff' prints all text
     following in bold until the next highlighting, paragraph, or
     heading macro.

 - Macro: .R [txt [post [pre]]]
     Sets its first argument in roman (or regular) type.  It operates
     similarly to the `B' macro otherwise.

 - Macro: .I [txt [post [pre]]]
     Sets its first argument in _italic type_.  It operates similarly
     to the `B' macro otherwise.

 - Macro: .CW [txt [post [pre]]]
     Sets its first argument in a `constant width face'.  It operates
     similarly to the `B' macro otherwise.

 - Macro: .BI [txt [post [pre]]]
     Sets its first argument in bold italic type.  It operates
     similarly to the `B' macro otherwise.

 - Macro: .BX [txt]
     Prints its argument and draws a box around it.  If you want to box
     a string that contains spaces, use a digit-width space (`\0').

 - Macro: .UL [txt [post]]
     Prints its first argument with an underline.  If you specify a
     second argument, `groff' prints it in the previous font after the
     underlined text, with no intervening space.

 - Macro: .LG
     Prints all text following in larger type (two points larger than
     the current point size) until the next font size, highlighting,
     paragraph, or heading macro.  You can specify this macro multiple
     times to enlarge the point size as needed.

 - Macro: .SM
     Prints all text following in smaller type (two points smaller than
     the current point size) until the next type size, highlighting,
     paragraph, or heading macro.  You can specify this macro multiple
     times to reduce the point size as needed.

 - Macro: .NL
     Prints all text following in the normal point size (that is, the
     value of the `PS' register).


File: groff,  Node: Lists in ms,  Next: Indents in ms,  Prev: Highlighting in ms,  Up: ms Body Text

Lists
.....

The `.IP' macro handles duties for all lists.

 - Macro: .IP [marker [width]]
     The MARKER is usually a bullet glyph (`\[bu]') for unordered
     lists, a number (or auto-incrementing number register) for
     numbered lists, or a word or phrase for indented (glossary-style)
     lists.

     The WIDTH specifies the indent for the body of each list item; its
     default unit is `n'.  Once specified, the indent remains the same
     for all list items in the document until specified again.

   The following is an example of a bulleted list.


     A bulleted list:
     .IP \[bu] 2
     lawyers
     .IP \[bu]
     guns
     .IP \[bu]
     money

   Produces:


     A bulleted list:
     
     o lawyers
     
     o guns
     
     o money


   The following is an example of a numbered list.


     .nr step 1 1
     A numbered list:
     .IP \n[step] 3
     lawyers
     .IP \n+[step]
     guns
     .IP \n+[step]
     money

   Produces:


     A numbered list:
     
     1. lawyers
     
     2. guns
     
     3. money

   Note the use of the auto-incrementing number register in this
example.


   The following is an example of a glossary-style list.


     A glossary-style list:
     .IP lawyers 0.4i
     Two or more attorneys.
     .IP guns
     Firearms, preferably
     large-caliber.
     .IP money
     Gotta pay for those
     lawyers and guns!

   Produces:


     A glossary-style list:
     
     lawyers
           Two or more attorneys.
     
     guns  Firearms, preferably large-caliber.
     
     money
           Gotta pay for those lawyers and guns!

   In the last example, the `IP' macro places the definition on the
same line as the term if it has enough space; otherwise, it breaks to
the next line and starts the definition below the term.  This may or
may not be the effect you want, especially if some of the definitions
break and some do not.  The following examples show two possible ways
to force a break.

   The first workaround uses the `br' request to force a break after
printing the term or label.


     A glossary-style list:
     .IP lawyers 0.4i
     Two or more attorneys.
     .IP guns
     .br
     Firearms, preferably large-caliber.
     .IP money
     Gotta pay for those lawyers and guns!


   The second workaround uses the `\p' escape to force the break.  Note
the space following the escape; this is important.  If you omit the
space, `groff' prints the first word on the same line as the term or
label (if it fits) *then* breaks the line.


     A glossary-style list:
     .IP lawyers 0.4i
     Two or more attorneys.
     .IP guns
     \p Firearms, preferably large-caliber.
     .IP money
     Gotta pay for those lawyers and guns!


   To set nested lists, use the `RS' and `RE' macros.  *Note Indents in
ms::, for more information.

   For example:


     .IP \[bu] 2
     Lawyers:
     .RS
     .IP \[bu]
     Dewey,
     .IP \[bu]
     Cheatham,
     .IP \[bu]
     and Howe.
     .RE
     .IP \[bu]
     Guns

   Produces:


     o Lawyers:
     
       o  Dewey,
     
       o  Cheatham,
     
       o  and Howe.
     
     o Guns


File: groff,  Node: Indents in ms,  Next: Tabstops in ms,  Prev: Lists in ms,  Up: ms Body Text

Indents
.......

In many situations, you may need to indent a section of text while
still wrapping and filling.  *Note Lists in ms::, for an example of
nested lists.

 - Macro: .RS
 - Macro: .RE
     These macros begin and end an indented section.  The `PI' register
     controls the amount of indent, allowing the indented text to line
     up under hanging and indented paragraphs.

   *Note ms Displays and Keeps::, for macros to indent and turn off
filling.


File: groff,  Node: Tabstops in ms,  Next: ms Displays and Keeps,  Prev: Indents in ms,  Up: ms Body Text

Tab Stops
.........

Use the `ta' request to define tab stops as needed.  *Note Tabs and
Fields::.

 - Macro: .TA
     Use this macro to reset the tab stops to the default for `ms'
     (every 5n).  You can redefine the `TA' macro to create a different
     set of default tab stops.


File: groff,  Node: ms Displays and Keeps,  Next: ms Insertions,  Prev: Tabstops in ms,  Up: ms Body Text

Displays and keeps
..................

Use displays to show text-based examples or figures (such as code
listings).

   Displays turn off filling, so lines of code are displayed as-is
without inserting `br' requests in between each line.  Displays can be
"kept" on a single page, or allowed to break across pages.

 - Macro: .DS L
 - Macro: .LD
 - Macro: .DE
     Left-justified display.  The `.DS L' call generates a page break,
     if necessary, to keep the entire display on one page.  The `LD'
     macro allows the display to break across pages.  The `DE' macro
     ends the display.

 - Macro: .DS I
 - Macro: .ID
 - Macro: .DE
     Indents the display as defined by the `DI' register.  The `.DS I'
     call generates a page break, if necessary, to keep the entire
     display on one page.  The `ID' macro allows the display to break
     across pages.  The `DE' macro ends the display.

 - Macro: .DS B
 - Macro: .BD
 - Macro: .DE
     Sets a block-centered display: the entire display is
     left-justified, but indented so that the longest line in the
     display is centered on the page.  The `.DS B' call generates a
     page break, if necessary, to keep the entire display on one page.
     The `BD' macro allows the display to break across pages.  The `DE'
     macro ends the display.

 - Macro: .DS C
 - Macro: .CD
 - Macro: .DE
     Sets a centered display: each line in the display is centered.
     The `.DS C' call generates a page break, if necessary, to keep the
     entire display on one page.  The `CD' macro allows the display to
     break across pages.  The `DE' macro ends the display.

 - Macro: .DS R
 - Macro: .RD
 - Macro: .DE
     Right-justifies each line in the display.  The `.DS R' call
     generates a page break, if necessary, to keep the entire display
     on one page.  The `RD' macro allows the display to break across
     pages.  The `DE' macro ends the display.

 - Macro: .Ds
 - Macro: .De
     These two macros are aliases for `DS' and `DE', respectively.


   On occasion, you may want to "keep" other text together on a page.
For example, you may want to keep two paragraphs together, or a
paragraph that refers to a table (or list, or other item) immediately
following.  The `ms' macros provide the `KS' and `KE' macros for this
purpose.

 - Macro: .KS
 - Macro: .KE
     The `KS' macro begins a block of text to be kept on a single page,
     and the `KE' macro ends the block.

 - Macro: .KF
 - Macro: .KE
     Specifies a "floating keep"; if the keep cannot fit on the current
     page, `groff' holds the contents of the keep and allows text
     following the keep (in the source file) to fill in the remainder of
     the current page.  When the page breaks, whether by an explicit
     `bp' request or by reaching the end of the page, `groff' prints
     the floating keep at the top of the new page.  This is useful for
     printing large graphics or tables that do not need to appear
     exactly where specified.

   You can also use the `ne' request to force a page break if there is
not enough vertical space remaining on the page.


   Use the following macros to draw a box around a section of text
(such as a display).

 - Macro: .B1
 - Macro: .B2
     Marks the beginning and ending of text that is to have a box drawn
     around it.  The `B1' macro begins the box; the `B2' macro ends it.
     Text in the box is automatically placed in a diversion (keep).


File: groff,  Node: ms Insertions,  Next: Example multi-page table,  Prev: ms Displays and Keeps,  Up: ms Body Text

Tables, figures, equations, and references
..........................................

The `ms' macros support the standard `groff' preprocessors: `tbl',
`pic', `eqn', and `refer'.  You mark text meant for preprocessors by
enclosing it in pairs of tags as follows.

 - Macro: .TS [`H']
 - Macro: .TE
     Denotes a table, to be processed by the `tbl' preprocessor.  The
     optional argument `H' to `TS' instructs `groff' to create a
     running header with the information up to the `TH' macro.  `groff'
     prints the header at the beginning of the table; if the table runs
     onto another page, `groff' prints the header on the next page as
     well.

 - Macro: .PS
 - Macro: .PE
     Denotes a graphic, to be processed by the `pic' preprocessor.  You
     can create a `pic' file by hand, using the AT&T `pic' manual
     available on the Web as a reference, or by using a graphics
     program such as `xfig'.

 - Macro: .EQ [align]
 - Macro: .EN
     Denotes an equation, to be processed by the `eqn' preprocessor.
     The optional ALIGN argument can be `C', `L', or `I' to center (the
     default), left-justify, or indent the equation.

 - Macro: .[
 - Macro: .]
     Denotes a reference, to be processed by the `refer' preprocessor.
     The GNU `refer(1)' man page provides a comprehensive reference to
     the preprocessor and the format of the bibliographic database.

* Menu:

* Example multi-page table::


File: groff,  Node: Example multi-page table,  Next: ms Footnotes,  Prev: ms Insertions,  Up: ms Body Text

An example multi-page table
...........................

The following is an example of how to set up a table that may print
across two or more pages.


     .TS H
     allbox expand;
     cb | cb .
     Text      ...of heading...
     _
     .TH
     .T&
     l | l .
     ... the rest of the table follows...
     .CW
     .TE


File: groff,  Node: ms Footnotes,  Prev: Example multi-page table,  Up: ms Body Text

Footnotes
.........

The `ms' macro package has a flexible footnote system.  You can specify
either numbered footnotes or symbolic footnotes (that is, using a
marker such as a dagger symbol).

 - String: \*[*]
     Specifies the location of a numbered footnote marker in the text.

 - Macro: .FS
 - Macro: .FE
     Specifies the text of the footnote.  The default action is to
     create a numbered footnote; you can create a symbolic footnote by
     specifying a "mark" glyph (such as `\[dg]' for the dagger glyph)
     in the body text and as an argument to the `FS' macro, followed by
     the text of the footnote and the `FE' macro.

   You can control how `groff' prints footnote numbers by changing the
value of the `FF' register.  *Note ms Document Control Registers::.


File: groff,  Node: ms Page Layout,  Next: Differences from AT&T ms,  Prev: ms Body Text,  Up: ms

Page layout
-----------

The default output from the `ms' macros provides a minimalist page
layout: it prints a single column, with the page number centered at the
top of each page.  It prints no footers.

   You can change the layout by setting the proper number registers and
strings.

* Menu:

* ms Headers and Footers::
* ms Margins::
* ms Multiple Columns::
* ms TOC::
* ms Strings and Special Characters::


File: groff,  Node: ms Headers and Footers,  Next: ms Margins,  Prev: ms Page Layout,  Up: ms Page Layout

Headers and footers
...................

For documents that do not distinguish between odd and even pages, set
the following strings:

 - String: \*[LH]
 - String: \*[CH]
 - String: \*[RH]
     Sets the left, center, and right headers.

 - String: \*[LF]
 - String: \*[CF]
 - String: \*[RF]
     Sets the left, center, and right footers.


   For documents that need different information printed in the even
and odd pages, use the following macros:

 - Macro: .OH 'left'center'right'
 - Macro: .EH 'left'center'right'
 - Macro: .OF 'left'center'right'
 - Macro: .EF 'left'center'right'
     The `OH' and `EH' macros define headers for the odd and even pages;
     the `OF' and `EF' macros define footers for the odd and even pages.
     This is more flexible than defining the individual strings.

     You can replace the quote (`'') marks with any character not
     appearing in the header or footer text.


File: groff,  Node: ms Margins,  Next: ms Multiple Columns,  Prev: ms Headers and Footers,  Up: ms Page Layout

Margins
.......

You control margins using a set of number registers.  *Note ms Document
Control Registers::, for details.


File: groff,  Node: ms Multiple Columns,  Next: ms TOC,  Prev: ms Margins,  Up: ms Page Layout

Multiple columns
................

The `ms' macros can set text in as many columns as will reasonably fit
on the page.  The following macros are available; all of them force a
page break if a multi-column mode is already set.  However, if the
current mode is single-column, starting a multi-column mode does *not*
force a page break.

 - Macro: .1C
     Single-column mode.

 - Macro: .2C
     Two-column mode.

 - Macro: .MC [width [gutter]]
     Multi-column mode.  If you specify no arguments, it is equivalent
     to the `2C' macro.  Otherwise, WIDTH is the width of each column
     and GUTTER is the space between columns.  The `MINGW' number
     register controls the default gutter width.


File: groff,  Node: ms TOC,  Next: ms Strings and Special Characters,  Prev: ms Multiple Columns,  Up: ms Page Layout

Creating a table of contents
............................

The facilities in the `ms' macro package for creating a table of
contents are semi-automated at best.  Assuming that you want the table
of contents to consist of the document's headings, you need to repeat
those headings wrapped in `XS' and `XE' macros.

 - Macro: .XS [page]
 - Macro: .XA [page]
 - Macro: .XE
     These macros define a table of contents or an individual entry in
     the table of contents, depending on their use.  The macros are
     very simple; they cannot indent a heading based on its level.  The
     easiest way to work around this is to add tabs to the table of
     contents string.  The following is an example:


          .NH 1
          Introduction
          .XS
          Introduction
          .XE
          .LP
          ...
          .CW
          .NH 2
          Methodology
          .XS
          Methodology
          .XE
          .LP
          ...

     You can manually create a table of contents by beginning with the
     `XS' macro for the first entry, specifying the page number for
     that entry as the argument to `XS'.  Add subsequent entries using
     the `XA' macro, specifying the page number for that entry as the
     argument to `XA'.  The following is an example:


          .XS 1
          Introduction
          .XA 2
          A Brief History of the Universe
          .XA 729
          Details of Galactic Formation
          ...
          .XE


 - Macro: .TC [`no']
     Prints the table of contents on a new page, setting the page
     number to *i* (Roman numeral one).  You should usually place this
     macro at the end of the file, since `groff' is a single-pass
     formatter and can only print what has been collected up to the
     point that the `TC' macro appears.

     The optional argument `no' suppresses printing the title specified
     by the string register `TOC'.

 - Macro: .PX [`no']
     Prints the table of contents on a new page, using the current page
     numbering sequence.  Use this macro to print a manually-generated
     table of contents at the beginning of your document.

     The optional argument `no' suppresses printing the title specified
     by the string register `TOC'.

   The `Groff and Friends HOWTO' includes a `sed' script that
automatically inserts `XS' and `XE' macro entries after each heading in
a document.

   Altering the `NH' macro to automatically build the table of contents
is perhaps initially more difficult, but would save a great deal of
time in the long run if you use `ms' regularly.


File: groff,  Node: ms Strings and Special Characters,  Prev: ms TOC,  Up: ms Page Layout

Strings and Special Characters
..............................

The `ms' macros provide the following predefined strings.  You can
change the string definitions to help in creating documents in
languages other than English.

 - String: \*[REFERENCES]
     Contains the string printed at the beginning of the references
     (bibliography) page.  The default is `References'.

 - String: \*[ABSTRACT]
     Contains the string printed at the beginning of the abstract.  The
     default is `ABSTRACT'.

 - String: \*[TOC]
     Contains the string printed at the beginning of the table of
     contents.

 - String: \*[MONTH1]
 - String: \*[MONTH2]
 - String: \*[MONTH3]
 - String: \*[MONTH4]
 - String: \*[MONTH5]
 - String: \*[MONTH6]
 - String: \*[MONTH7]
 - String: \*[MONTH8]
 - String: \*[MONTH9]
 - String: \*[MONTH10]
 - String: \*[MONTH11]
 - String: \*[MONTH12]
     Prints the full name of the month in dates.  The default is
     `January', `February', etc.

   The following special characters are available(1) (*note ms Strings
and Special Characters-Footnote-1::):

 - String: \*[-]
     Prints an em dash.

 - String: \*[*Q]
 - String: \*[*U]
     Prints typographer's quotes in troff, plain quotes in nroff.  `*Q'
     is the left quote and `*U' is the right quote.

   Improved accent marks are available in the `ms' macros.

 - Macro: .AM
     Specify this macro at the beginning of your document to enable
     extended accent marks and special characters.  This is a Berkeley
     extension.

     To use the accent marks, place them *after* the character being
     accented.

   The following accent marks are available after invoking the `AM'
macro:

 - String: \*[']
     Acute accent.

 - String: \*[`]
     Grave accent.

 - String: \*[^]
     Circumflex.

 - String: \*[,]
     Cedilla.

 - String: \*[~]
     Tilde.

 - String: \*[:]
     Umlaut.

 - String: \*[v]
     Hacek.

 - String: \*[_]
     Macron (overbar).

 - String: \*[.]
     Underdot.

 - String: \*[o]
     Ring above.

   The following are standalone characters available after invoking the
`AM' macro:

 - String: \*[?]
     Upside-down question mark.

 - String: \*[!]
     Upside-down exclamation point.

 - String: \*[8]
     German ss ligature.

 - String: \*[3]
     Yogh.

 - String: \*[Th]
     Uppercase thorn.

 - String: \*[th]
     Lowercase thorn.

 - String: \*[D-]
     Uppercase eth.

 - String: \*[d-]
     Lowercase eth.

 - String: \*[q]
     Hooked o.

 - String: \*[ae]
     Lowercase ae ligature.

 - String: \*[Ae]
     Uppercase AE ligature.


File: groff,  Node: ms Strings and Special Characters-Footnotes,  Up: ms Strings and Special Characters

   (1) For an explanation what special characters are see *Note Special
Characters::.


File: groff,  Node: Differences from AT&T ms,  Prev: ms Page Layout,  Up: ms

Differences from AT&T `ms'
--------------------------

This section lists the (minor) differences between the `groff -ms'
macros and AT&T `troff -ms' macros.

* Menu:

* Missing ms Macros::
* Additional ms Macros::


File: groff,  Node: Missing ms Macros,  Next: Additional ms Macros,  Prev: Differences from AT&T ms,  Up: Differences from AT&T ms

`troff' macros not appearing in `groff'
.......................................

Macros missing from `groff -ms' are cover page macros specific to Bell
Labs.  The macros known to be missing are:

`.TM'
     Technical memorandum; a cover sheet style

`.IM'
     Internal memorandum; a cover sheet style

`.MR'
     Memo for record; a cover sheet style

`.MF'
     Memo for file; a cover sheet style

`.EG'
     Engineer's notes; a cover sheet style

`.TR'
     Computing Science Tech Report; a cover sheet style

`.OK'
     Other keywords

`.CS'
     Cover sheet information

`.MH'
     A cover sheet macro


File: groff,  Node: Additional ms Macros,  Prev: Missing ms Macros,  Up: Differences from AT&T ms

`groff' macros not appearing in AT&T `troff'
............................................

The `groff -ms' macros have a few minor extensions compared to the AT&T
`troff -ms' macros.

 - Macro: .AM
     Improved accent marks.  *Note ms Strings and Special Characters::,
     for details.

 - Macro: .DS I
     Indented display.  The default behavior of AT&T `troff -ms' was to
     indent; the `groff' default prints displays flush left with the
     body text.

 - Macro: .CW
     Print text in `constant width' (Courier) font.

 - Macro: .IX
     Indexing term (printed on standard error).  You can write a script
     to capture and process an index generated in this manner.


   The following additional number registers appear in `groff -ms':

 - Register: \n[MINGW]
     Specifies a minimum space between columns (for multi-column
     output); this takes the place of the `GW' register that was
     documented but apparently not implemented in AT&T `troff'.


   Several new string registers are available as well.  You can change
these to handle (for example) the local language.  *Note ms Strings and
Special Characters::, for details.


File: groff,  Node: me,  Next: mm,  Prev: ms,  Up: Macro Packages

`me'
====

See the `meintro.me' and `meref.me' documents in groff's `doc'
directory.


File: groff,  Node: mm,  Prev: me,  Up: Macro Packages

`mm'
====

See the `groff_mm(7)' man page (type `man groff_mm' at the command
line).


File: groff,  Node: gtroff Reference,  Next: Preprocessors,  Prev: Macro Packages,  Up: Top

`gtroff' Reference
******************

This chapter covers *all* of the facilities of `gtroff'.  Users of
macro packages may skip it if not interested in details.

* Menu:

* Text::
* Measurements::
* Expressions::
* Identifiers::
* Embedded Commands::
* Registers::
* Manipulating Filling and Adjusting::
* Manipulating Hyphenation::
* Manipulating Spacing::
* Tabs and Fields::
* Character Translations::
* Troff and Nroff Mode::
* Line Layout::
* Line Control::
* Page Layout::
* Page Control::
* Fonts and Symbols::
* Sizes::
* Strings::
* Conditionals and Loops::
* Writing Macros::
* Page Motions::
* Drawing Requests::
* Traps::
* Diversions::
* Environments::
* Suppressing output::
* Colors::
* I/O::
* Postprocessor Access::
* Miscellaneous::
* Gtroff Internals::
* Debugging::
* Implementation Differences::


File: groff,  Node: Text,  Next: Measurements,  Prev: gtroff Reference,  Up: gtroff Reference

Text
====

`gtroff' input files contain text with control commands interspersed
throughout.  But, even without control codes, `gtroff' still does
several things with the input text:

   * filling and adjusting

   * adding additional space after sentences

   * hyphenating

   * inserting implicit line breaks

* Menu:

* Filling and Adjusting::
* Hyphenation::
* Sentences::
* Tab Stops::
* Implicit Line Breaks::
* Input Conventions::
* Input Encodings::


File: groff,  Node: Filling and Adjusting,  Next: Hyphenation,  Prev: Text,  Up: Text

Filling and Adjusting
---------------------

When `gtroff' reads text, it collects words from the input and fits as
many of them together on one output line as it can.  This is known as
"filling".

   Once `gtroff' has a "filled" line, it tries to "adjust" it.  This
means it widens the spacing between words until the text reaches the
right margin (in the default adjustment mode).  Extra spaces between
words are preserved, but spaces at the end of lines are ignored.
Spaces at the front of a line cause a "break" (breaks are explained in
*Note Implicit Line Breaks::).

   *Note Manipulating Filling and Adjusting::.


File: groff,  Node: Hyphenation,  Next: Sentences,  Prev: Filling and Adjusting,  Up: Text

Hyphenation
-----------

Since the odds are not great for finding a set of words, for every
output line, which fit nicely on a line without inserting excessive
amounts of space between words, `gtroff' hyphenates words so that it
can justify lines without inserting too much space between words.  It
uses an internal hyphenation algorithm (a simplified version of the
algorithm used within TeX) to indicate which words can be hyphenated
and how to do so.  When a word is hyphenated, the first part of the
word is added to the current filled line being output (with an attached
hyphen), and the other portion is added to the next line to be filled.

   *Note Manipulating Hyphenation::.


File: groff,  Node: Sentences,  Next: Tab Stops,  Prev: Hyphenation,  Up: Text

Sentences
---------

Although it is often debated, some typesetting rules say there should be
different amounts of space after various punctuation marks.  For
example, the `Chicago typsetting manual' says that a period at the end
of a sentence should have twice as much space following it as would a
comma or a period as part of an abbreviation.

   `gtroff' does this by flagging certain characters (normally `!',
`?', and `.') as "end-of-sentence" characters.  When `gtroff'
encounters one of these characters at the end of a line, it appends a
normal space followed by a "sentence space" in the formatted output.
(This justifies one of the conventions mentioned in *Note Input
Conventions::.)

   In addition, the following characters and symbols are treated
transparently while handling end-of-sentence characters: `"', `'', `)',
`]', `*', `\[dg]', and `\[rq]'.

   See the `cflags' request in *Note Using Symbols::, for more details.

   To prevent the insertion of extra space after an end-of-sentence
character (at the end of a line), append `\&'.


File: groff,  Node: Tab Stops,  Next: Implicit Line Breaks,  Prev: Sentences,  Up: Text

Tab Stops
---------

`gtroff' translates "tabulator characters", also called "tabs"
(normally code point ASCII `0x09' or EBCDIC `0x05'), in the input into
movements to the next tabulator stop.  These tab stops are initially
located every half inch across the page.  Using this, simple tables can
be made easily.  However, it can often be deceptive as the appearance
(and width) of the text on a terminal and the results from `gtroff' can
vary greatly.

   Also, a possible sticking point is that lines beginning with tab
characters are still filled, again producing unexpected results.  For
example, the following input

           1          2          3
                      4          5

produces

           1          2          3                     4          5

   *Note Tabs and Fields::.


File: groff,  Node: Implicit Line Breaks,  Next: Input Conventions,  Prev: Tab Stops,  Up: Text

Implicit Line Breaks
--------------------

An important concept in `gtroff' is the "break".  When a break occurs,
`gtroff' outputs the partially filled line (unjustified), and resumes
collecting and filling text on the next output line.

   There are several ways to cause a break in `gtroff'.  A blank line
not only causes a break, but it also outputs a one-line vertical space
(effectively a blank line).  Note that this behaviour can be modified
with the blank line macro request `blm'.  *Note Blank Line Traps::.

   A line that begins with a space causes a break and the space is
output at the beginning of the next line.  Note that this space isn't
adjusted, even in fill mode.

   The end of file also causes a break - otherwise the last line of the
document may vanish!

   Certain requests also cause breaks, implicitly or explicitly.  This
is discussed in *Note Manipulating Filling and Adjusting::.


File: groff,  Node: Input Conventions,  Next: Input Encodings,  Prev: Implicit Line Breaks,  Up: Text

Input Conventions
-----------------

Since `gtroff' does filling automatically, it is traditional in `groff'
not to try and type things in as nicely formatted paragraphs.  These
are some conventions commonly used when typing `gtroff' text:

   * Break lines after punctuation, particularly at the end of a
     sentence and in other logical places.  Keep separate phrases on
     lines by themselves, as entire phrases are often added or deleted
     when editing.

   * Try to keep lines less than 40-60 characters, to allow space for
     inserting more text.

   * Do not try to do any formatting in a WYSIWYG manner (i.e., don't
     try using spaces to get proper indentation).


File: groff,  Node: Input Encodings,  Prev: Input Conventions,  Up: Text

Input Encodings
---------------

Currently, the following input encodings are available.

cp1047
     This input encoding works only on EBCDIC platforms (and vice
     versa, the other input encodings don't work with EBCDIC); the file
     `cp1047.tmac' is by default loaded at start-up.

latin-1
     This is the default input encoding on non-EBCDIC platforms; the
     file `latin1.tmac' is loaded at start-up.

latin-2
     To use this encoding, either say `.mso latin2.tmac' at the very
     beginning of your document or use `-mlatin2' as a command line
     argument for `groff'.

latin-9 (latin-0)
     This encoding is intended (at least in Europe) to replace latin-1
     encoding.  The main difference to latin-1 is that latin-9 contains
     the Euro character.  To use this encoding, either say
     `.mso latin9.tmac' at the very beginning of your document or use
     `-mlatin9' as a command line argument for `groff'.

   Note that it can happen that some input encoding characters are not
available for a particular output device.  For example, saying


     groff -Tlatin1 -mlatin9 ...

will fail if you use the Euro character in the input.  Usually, this
limitation is present only for devices which have a limited set of
output glyphs (e.g. `-Tascii' and `-Tlatin1'); for other devices it is
usually sufficient to install proper fonts which contain the necessary
glyphs.

   Due to the importance of the Euro glyph in Europe, the groff package
now comes with a POSTSCRIPT font called `freeeuro.pfa' which provides
various glyph shapes for the Euro.  With other words, latin-9 encoding
is supported for the `-Tps' device out of the box (latin-2 isn't).

   By its very nature, `-Tutf8' supports all input encodings; `-Tdvi'
has support for both latin-2 and latin-9 if the command line `-mec' is
used also to load the file `ec.tmac' (which flips to the EC fonts).


File: groff,  Node: Measurements,  Next: Expressions,  Prev: Text,  Up: gtroff Reference

Measurements
============

`gtroff' (like many other programs) requires numeric parameters to
specify various measurements.  Most numeric parameters(1) (*note
Measurements-Footnote-1::) may have a "measurement unit" attached.
These units are specified as a single character which immediately
follows the number or expression.  Each of these units are understood,
by `gtroff', to be a multiple of its "basic unit".  So, whenever a
different measurement unit is specified `gtroff' converts this into its
"basic units".  This basic unit, represented by a `u', is a device
dependent measurement which is quite small, ranging from 1/75th to
1/72000th of an inch.  The values may be given as fractional numbers;
however, fractional basic units are always rounded to integers.

   Some of the measurement units are completely independent of any of
the current settings (e.g. type size) of `gtroff'.

`i'
     Inches.  An antiquated measurement unit still in use in certain
     backwards countries with incredibly low-cost computer equipment.
     One inch is equal to 2.54cm.

`c'
     Centimeters.  One centimeter is equal to 0.3937in.

`p'
     Points.  This is a typesetter's measurement used for measure type
     size.  It is 72 points to an inch.

`P'
     Pica.  Another typesetting measurement.  6 Picas to an inch (and
     12 points to a pica).

`s'
`z'
     *Note Fractional Type Sizes::, for a discussion of these units.

`f'
     Fractions. Value is 65536.  *Note Colors::, for usage.

   The other measurements understood by `gtroff' depend on settings
currently in effect in `gtroff'.  These are very useful for specifying
measurements which should look proper with any size of text.

`m'
     Ems.  This unit is equal to the current font size in points.  So
     called because it is _approximately_ the width of the letter `m'
     in the current font.

`n'
     Ens.  In `groff', this is half of an em.

`v'
     Vertical space.  This is equivalent to the current line spacing.
     *Note Sizes::, for more information about this.

`M'
     100ths of an em.

* Menu:

* Default Units::


File: groff,  Node: Measurements-Footnotes,  Up: Measurements

   (1) those that specify vertical or horizontal motion or a type size


File: groff,  Node: Default Units,  Prev: Measurements,  Up: Measurements

Default Units
-------------

Many requests take a default unit.  While this can be helpful at times,
it can cause strange errors in some expressions.  For example, the line
length request expects em units.  Here are several attempts to get a
line length of 3.5 inches and their results:


     3.5i      =>   3.5i
     7/2       =>   0i
     7/2i      =>   0i
     (7 / 2)u  =>   0i
     7i/2      =>   0.1i
     7i/2u     =>   3.5i

Everything is converted to basic units first.  In the above example it
is assumed that 1i equals 240u, and 1m equals 10p (thus 1m equals 33u).
The value 7i/2 is first handled as 7i/2m, then converted to 1680u/66u
which is 25u, and this is approximately 0.1i.  As can be seen, a
scaling indicator after a closing parenthesis is simply ignored.

   Thus, the safest way to specify measurements is to always attach a
scaling indicator.  If you want to multiply or divide by a certain
scalar value, use `u' as the unit for that value.


File: groff,  Node: Expressions,  Next: Identifiers,  Prev: Measurements,  Up: gtroff Reference

Expressions
===========

`gtroff' has most arithmetic operators common to other languages:

   * Arithmetic: `+' (addition), `-' (subtraction), `/' (division), `*'
     (multiplication), `%' (modulo).

     `gtroff' only provides integer arithmetic.  The internal type used
     for computing results is `int', which is usually a 32bit signed
     integer.

   * Comparison: `<' (less than), `>' (greater than), `<=' (less than
     or equal), `>=' (greater than or equal), `=' (equal), `==' (the
     same as `=').

   * Logical: `&' (logical and), `:' (logical or).

   * Unary operators: `-' (negating, i.e. changing the sign), `+' (just
     for completeness; does nothing in expressions), `!' (logical not;
     this works only within `if' and `while' requests).  See below for
     the use of unary operators in motion requests.

   * Extrema: `>?' (maximum), `<?' (minimum).

     Example:


          .nr x 5
          .nr y 3
          .nr z (\n[x] >? \n[y])

     The register `z' now contains 5.

   * Scaling: `(C;E)'.  Evaluate E using C as the default scaling
     indicator.  If C is missing, ignore scaling indicators in the
     evaluation of E.

   Parentheses may be used as in any other language.  However, in
`gtroff' they are necessary to ensure order of evaluation.  `gtroff'
has no operator precedence; expressions are evaluated left to right.
This means that `gtroff' evaluates `3+5*4' as if it were parenthesized
like `(3+5)*4', not as `3+(5*4)', as might be expected.

   For many requests which cause a motion on the page, the unary
operators `+' and `-' work differently if leading an expression.  They
then indicate a motion relative to the current position (down or up,
respectively).

   Similarly, a leading `|' operator indicates an absolute position.
For vertical movements, it specifies the distance from the top of the
page; for horizontal movements, it gives the distance from the beginning
of the _input_ line.

   `+' and `-' are also treated differently by the following requests
and escapes: `bp', `in', `ll', `lt', `nm', `nr', `pl', `pn', `po', `ps',
`pvs', `rt', `ti', `\H', `\R', and `\s'.  Here, leading plus and minus
signs indicate increments and decrements.

   *Note Setting Registers::, for some examples.

 - Escape: \B'anything'
     Return 1 if ANYTHING is a valid numeric expression; or 0 if
     ANYTHING is empty or not a valid numeric expression.

   Due to the way arguments are parsed, spaces are not allowed in
expressions, unless the entire expression is surrounded by parentheses.

   *Note Request and Macro Arguments::, and *Note Conditionals and
Loops::.


File: groff,  Node: Identifiers,  Next: Embedded Commands,  Prev: Expressions,  Up: gtroff Reference

Identifiers
===========

Like any other language, `gtroff' has rules for properly formed
"identifiers".  In `gtroff', an identifier can be made up of almost any
printable character, with the exception of the following characters:

   * Whitespace characters (spaces, tabs, and newlines).

   * Backspace (ASCII `0x08' or EBCDIC `0x16') and character code
     `0x01'.

   * The following input characters are invalid and are ignored if
     `groff' runs on a machine based on ASCII, causing a warning
     message of type `input' (see *Note Debugging::, for more details):
     `0x00', `0x0B', `0x0D'-`0x1F', `0x80'-`0x9F'.

     And here are the invalid input characters if `groff' runs on an
     EBCDIC host: `0x00', `0x08', `0x09', `0x0B', `0x0D'-`0x14',
     `0x17'-`0x1F', `0x30'-`0x3F'.

     Currently, some of these reserved codepoints are used internally,
     thus making it non-trivial to extend `gtroff' to cover Unicode or
     other character sets and encodings which use characters of these
     ranges.

     Note that invalid characters are removed before parsing; an
     identifier `foo', followed by an invalid character, followed by
     `bar' is treated as `foobar'.

   For example, any of the following is valid.


     br
     PP
     (l
     end-list
     @_

Note that identifiers longer than two characters with a closing bracket
(`]') in its name can't be accessed with escape sequences which expect
an identifier as a parameter.  For example, `\[foo]]' accesses the
glyph `foo', followed by `]', whereas `\C'foo]'' really asks for glyph
`foo]'.

   To avoid problems with the `refer' preprocessor, macro names should
not start with `[' or `]'.  Due to backwards compatibility, everything
after `.[' and `.]' is handled as a special argument to `refer'.  For
example, `.[foo' makes `refer' to start a reference, using `foo' as a
parameter.

 - Escape: \A'ident'
     Test whether an identifier IDENT is valid in `gtroff'.  It expands
     to the character 1 or 0 according to whether its argument (usually
     delimited by quotes) is or is not acceptable as the name of a
     string, macro, diversion, number register, environment, or font.
     It returns 0 if no argument is given.  This is useful for looking
     up user input in some sort of associative table.


          \A'end-list'
              => 1


   *Note Escapes::, for details on parameter delimiting characters.

   Identifiers in `gtroff' can be any length, but, in some contexts,
`gtroff' needs to be told where identifiers end and text begins (and in
different ways depending on their length):

   * Single character.

   * Two characters.  Must be prefixed with `(' in some situations.

   * Arbitrary length (`gtroff' only).  Must be bracketed with `['
     and `]' in some situations.  Any length identifier can be put in
     brackets.

   Unlike many other programming languages, undefined identifiers are
silently ignored or expanded to nothing.  When `gtroff' finds an
undefined identifier, it emits a warning, doing the following:

   * If the identifier is a string, macro, or diversion, `gtroff'
     defines it as empty.

   * If the identifier is a number register, `gtroff' defines it with a
     value of 0.

   *Note Warnings::., *Note Interpolating Registers::, and *Note
Strings::.

   Note that macros, strings, and diversions share the same name space.


     .de xxx
     .  nop foo
     ..
     .
     .di xxx
     bar
     .br
     .di
     .
     .xxx
         => bar

As can be seen in the previous example, `gtroff' reuses the identifier
`xxx', changing it from a macro to a diversion.  No warning is emitted!
The contents of the first macro definition is lost.

   *Note Interpolating Registers::, and *Note Strings::.


File: groff,  Node: Embedded Commands,  Next: Registers,  Prev: Identifiers,  Up: gtroff Reference

Embedded Commands
=================

Most documents need more functionality beyond filling, adjusting and
implicit line breaking.  In order to gain further functionality,
`gtroff' allows commands to be embedded into the text, in two ways.

   The first is a "request" which takes up an entire line, and does
some large-scale operation (e.g. break lines, start new pages).

   The other is an "escape" which can be usually embedded anywhere in
the text; most requests can accept it even as an argument.  Escapes
generally do more minor operations like sub- and superscripts, print a
symbol, etc.

* Menu:

* Requests::
* Macros::
* Escapes::


File: groff,  Node: Requests,  Next: Macros,  Prev: Embedded Commands,  Up: Embedded Commands

Requests
--------

A request line begins with a control character, which is either a single
quote (`'', the "no-break control character") or a period (`.', the
normal "control character").  These can be changed; see *Note Character
Translations::, for details.  After this there may be optional tabs or
spaces followed by an identifier which is the name of the request.
This may be followed by any number of space-separated arguments (_no_
tabs here).

   Since a control character followed by whitespace only is ignored, it
is common practice to use this feature for structuring the source code
of documents or macro packages.


     .de foo
     .  tm This is foo.
     ..
     .
     .
     .de bar
     .  tm This is bar.
     ..

   Another possibility is to use the blank line macro request `blm' by
assigning an empty macro to it.


     .de do-nothing
     ..
     .blm do-nothing  \" activate blank line macro
     
     .de foo
     .  tm This is foo.
     ..
     
     
     .de bar
     .  tm This is bar.
     ..
     
     .blm             \" deactivate blank line macro

   *Note Blank Line Traps::.

   To begin a line with a control character without it being
interpreted, precede it with `\&'.  This represents a zero width space,
which means it does not affect the output.

   In most cases the period is used as a control character.  Several
requests cause a break implicitly; using the single quote control
character prevents this.

* Menu:

* Request and Macro Arguments::


File: groff,  Node: Request and Macro Arguments,  Prev: Requests,  Up: Requests

Request and Macro Arguments
...........................

Arguments to requests and macros are processed much like the shell: The
line is split into arguments according to spaces.(1) (*note Request and
Macro Arguments-Footnote-1::)

   An argument to a macro which is intended to contain spaces can
either be enclosed in double quotes, or have the spaces "escaped" with
backslashes.  This is _not_ true for requests.

   Here are a few examples for a hypothetical macro `uh':


     .uh The Mouse Problem
     .uh "The Mouse Problem"
     .uh The\ Mouse\ Problem

The first line is the `uh' macro being called with 3 arguments, `The',
`Mouse', and `Problem'.  The latter two have the same effect of calling
the `uh' macro with one argument, `The Mouse Problem'.(2) (*note
Request and Macro Arguments-Footnote-2::)

   A double quote which isn't preceded by a space doesn't start a macro
argument.  If not closing a string, it is printed literally.

   For example,


     .xxx a" "b c" "de"fg"

has the arguments `a"', `b c', `de', and `fg"'.  Don't rely on this
obscure behaviour!

   There are two possibilities to get a double quote reliably.

   * Enclose the whole argument with double quotes and use two
     consecutive double quotes to represent a single one.  This
     traditional solution has the disadvantage that double quotes don't
     survive argument expansion again if called in compatibility mode
     (using the `-C' option of `groff'):


          .de xx
          .  tm xx: `\\$1' `\\$2' `\\$3'
          .
          .  yy "\\$1" "\\$2" "\\$3"
          ..
          .de yy
          .  tm yy: `\\$1' `\\$2' `\\$3'
          ..
          .xx A "test with ""quotes""" .
              => xx: `A' `test with "quotes"' `.'
              => yy: `A' `test with ' `quotes""'

     If not in compatibility mode, you get the expected result


          xx: `A' `test with "quotes"' `.'
          yy: `A' `test with "quotes"' `.'

     since `gtroff' preserves the input level.

   * Use the double quote glyph `\(dq'.  This works with and without
     compatibility mode enabled since `gtroff' doesn't convert `\(dq'
     back to a double quote input character.

     Not that this method won't work with UNIX `troff' in general since
     the glyph `dq' isn't defined normally.

   Double quotes in the `ds' request are handled differently.  *Note
Strings::, for more details.


File: groff,  Node: Request and Macro Arguments-Footnotes,  Up: Request and Macro Arguments

   (1) Plan 9's `troff' implementation also allows tabs for argument
separation - `gtroff' intentionally doesn't support this.

   (2) The last solution, i.e., using escaped spaces, is "classical" in
the sense that it can be found in most `troff' documents.
Nevertheless, it is not optimal in all situations, since `\ ' inserts a
fixed-width, non-breaking space character which can't stretch.
`gtroff' provides a different command `\~' to insert a stretchable,
non-breaking space.


File: groff,  Node: Macros,  Next: Escapes,  Prev: Requests,  Up: Embedded Commands

Macros
------

`gtroff' has a "macro" facility for defining a series of lines which
can be invoked by name.  They are called in the same manner as requests
- arguments also may be passed basically in the same manner.

   *Note Writing Macros::, and *Note Request and Macro Arguments::.


File: groff,  Node: Escapes,  Prev: Macros,  Up: Embedded Commands

Escapes
-------

Escapes may occur anywhere in the input to `gtroff'.  They usually
begin with a backslash and are followed by a single character which
indicates the function to be performed.  The escape character can be
changed; see *Note Character Translations::.

   Escape sequences which require an identifier as a parameter accept
three possible syntax forms.

   * The next single character is the identifier.

   * If this single character is an opening parenthesis, take the
     following two characters as the identifier.  Note that there is no
     closing parenthesis after the identifier.

   * If this single character is an opening bracket, take all characters
     until a closing bracket as the identifier.

Examples:


     \fB
     \n(XX
     \*[TeX]

   Other escapes may require several arguments and/or some special
format.  In such cases the argument is traditionally enclosed in single
quotes (and quotes are always used in this manual for the definitions
of escape sequences).  The enclosed text is then processed according to
what that escape expects.  Example:


     \l'1.5i\(bu'

   Note that the quote character can be replaced with any other
character which does not occur in the argument (even a newline or a
space character) in the following escapes: `\o', `\b', and `\X'.  This
makes e.g.


     A caf
     \o
     e\'
     
     
     in Paris
       => A cafe' in Paris

possible, but it is better not to use this feature to avoid confusion.

   The following escapes sequences (which are handled similarly to
characters since they don't take a parameter) are also allowed as
delimiters: `\%', `\ ', `\|', `\^', `\{', `\}', `\'', `\`', `\-', `\_',
`\!', `\?', `\@', `\)', `\/', `\,', `\&', `\:', `\~', `\0', `\a', `\c',
`\d', `\e', `\E', `\p', `\r', `\t', and `\u'.  Again, don't use these
if possible.

   No newline characters as delimiters are allowed in the following
escapes: `\A', `\B', `\Z', `\C', and `\w'.

   Finally, the escapes `\D', `\h', `\H', `\l', `\L', `\N', `\R', `\s',
`\S', `\v', and `\x' can't use the following characters as delimiters:

   * The digits `0'-`9'.

   * The (single-character) operators `+-/*%<>=&:().'.

   * The space, tab, and newline characters.

   * All escape sequences except `\%', `\:', `\{', `\}', `\'', `\`',
     `\-', `\_', `\!', `\@', `\/', `\c', `\e', and `\p'.

   To have a backslash (actually, the current escape character) appear
in the output several escapes are defined: `\\', `\e' or `\E'.  These
are very similar, and only differ with respect to being used in macros
or diversions.  *Note Character Translations::, for an exact
description of those escapes.

   *Note Implementation Differences::, *Note Copy-in Mode::, and *Note
Diversions::, *Note Identifiers::, for more information.

* Menu:

* Comments::


File: groff,  Node: Comments,  Prev: Escapes,  Up: Escapes

Comments
........

Probably one of the most(1) (*note Comments-Footnote-1::) common forms
of escapes is the comment.

 - Escape: \"
     Start a comment.  Everything to the end of the input line is
     ignored.

     This may sound simple, but it can be tricky to keep the comments
     from interfering with the appearance of the final output.

     If the escape is to the right of some text or a request, that
     portion of the line is ignored, but the space leading up to it is
     noticed by `gtroff'.  This only affects the `ds' and `as' request
     and its variants.

     One possibly irritating idiosyncracy is that tabs must not be used
     to line up comments.  Tabs are not treated as whitespace between
     the request and macro arguments.

     A comment on a line by itself is treated as a blank line, because
     after eliminating the comment, that is all that remains:


          Test
          \" comment
          Test

     produces


          Test
          
          Test

     To avoid this, it is common to start the line with `.\"' which
     causes the line to be treated as an undefined request and thus
     ignored completely.

     Another commenting scheme seen sometimes is three consecutive
     single quotes (`'''') at the beginning of a line.  This works, but
     `gtroff' gives a warning about an undefined macro (namely `'''),
     which is harmless, but irritating.

 - Escape: \#
     To avoid all this, `gtroff' has a new comment mechanism using the
     `\#' escape.  This escape works the same as `\"' except that the
     newline is also ignored:


          Test
          \# comment
          Test

     produces


          Test Test

     as expected.

 - Request: .ig [end]
     Ignore all input until `gtroff' encounters the macro named `.'END
     on a line by itself (or `..' if END is not specified).  This is
     useful for commenting out large blocks of text:


          text text text...
          .ig
          This is part of a large block
          of text that has been
          temporarily(?) commented out.
          
          We can restore it simply by removing
          the .ig request and the ".." at the
          end of the block.
          ..
          More text text text...

     produces


          text text text...  More text text text...

     Note that the commented-out block of text does not cause a break.

     The input is read in copy-mode; auto-incremented registers _are_
     affected (*note Auto-increment::).


File: groff,  Node: Comments-Footnotes,  Up: Comments

   (1) Unfortunately, this is a lie.  But hopefully future `gtroff'
hackers will believe it `:-)'


File: groff,  Node: Registers,  Next: Manipulating Filling and Adjusting,  Prev: Embedded Commands,  Up: gtroff Reference

Registers
=========

Numeric variables in `gtroff' are called "registers".  There are a
number of built-in registers, supplying anything from the date to
details of formatting parameters.

   *Note Identifiers::, for details on register identifiers.

* Menu:

* Setting Registers::
* Interpolating Registers::
* Auto-increment::
* Assigning Formats::
* Built-in Registers::


File: groff,  Node: Setting Registers,  Next: Interpolating Registers,  Prev: Registers,  Up: Registers

Setting Registers
-----------------

Define or set registers using the `nr' request or the `\R' escape.

 - Request: .nr ident value
 - Escape: \R'ident value'
     Set number register IDENT to VALUE.  If IDENT doesn't exist,
     `gtroff' creates it.

     The argument to `\R' usually has to be enclosed in quotes.  *Note
     Escapes::, for details on parameter delimiting characters.

     The `\R' escape doesn't produce an input token in `gtroff'; with
     other words, it vanishes completely after `gtroff' has processed
     it.

   For example, the following two lines are equivalent:


     .nr a (((17 + (3 * 4))) % 4)
     \R'a (((17 + (3 * 4))) % 4)'
         => 1

   Both `nr' and `\R' have two additional special forms to increment or
decrement a register.

 - Request: .nr ident +value
 - Request: .nr ident -value
 - Escape: \R'ident +value'
 - Escape: \R'ident -value'
     Increment (decrement) register IDENT by VALUE.


          .nr a 1
          .nr a +1
          \na
              => 2

     To assign the negated value of a register to another register,
     some care must be taken to get the desired result:


          .nr a 7
          .nr b 3
          .nr a -\nb
          \na
              => 4
          .nr a (-\nb)
          \na
              => -3

     The surrounding parentheses prevent the interpretation of the
     minus sign as a decrementing operator.  An alternative is to start
     the assignment with a `0':


          .nr a 7
          .nr b -3
          .nr a \nb
          \na
              => 4
          .nr a 0\nb
          \na
              => -3


 - Request: .rr ident
     Remove number register IDENT.  If IDENT doesn't exist, the request
     is ignored.

 - Request: .rnn ident1 ident2
     Rename number register IDENT1 to IDENT2.  If either IDENT1 or
     IDENT2 doesn't exist, the request is ignored.

 - Request: .aln ident1 ident2
     Create an alias IDENT1 for a number register IDENT2.  The new name
     and the old name are exactly equivalent.  If IDENT1 is undefined,
     a warning of type `reg' is generated, and the request is ignored.
     *Note Debugging::, for information about warnings.


File: groff,  Node: Interpolating Registers,  Next: Auto-increment,  Prev: Setting Registers,  Up: Registers

Interpolating Registers
-----------------------

Numeric registers can be accessed via the `\n' escape.

 - Escape: \ni
 - Escape: \n(id
 - Escape: \n[ident]
     Interpolate number register with name IDENT (one-character name I,
     two-character name ID).  This means that the value of the register
     is expanded in-place while `gtroff' is parsing the input line.
     Nested assignments (also called indirect assignments) are possible.


          .nr a 5
          .nr as \na+\na
          \n(as
              => 10


          .nr a1 5
          .nr ab 6
          .ds str b
          .ds num 1
          \n[a\n[num]]
              => 5
          \n[a\*[str]]
              => 6



File: groff,  Node: Auto-increment,  Next: Assigning Formats,  Prev: Interpolating Registers,  Up: Registers

Auto-increment
--------------

Number registers can also be auto-incremented and auto-decremented.
The increment or decrement value can be specified with a third argument
to the `nr' request or `\R' escape.

 - Request: .nr ident value incr
     Set number register IDENT to VALUE; the increment for
     auto-incrementing is set to INCR.  Note that the `\R' escape
     doesn't support this notation.

   To activate auto-incrementing, the escape `\n' has a special syntax
form.

 - Escape: \n+i
 - Escape: \n-i
 - Escape: \n(+id
 - Escape: \n(-id
 - Escape: \n+(id
 - Escape: \n-(id
 - Escape: \n[+ident]
 - Escape: \n[-ident]
 - Escape: \n+[ident]
 - Escape: \n-[ident]
     Before interpolating, increment or decrement IDENT (one-character
     name I, two-character name ID) by the auto-increment value as
     specified with the `nr' request (or the `\R' escape).  If no
     auto-increment value has been specified, these syntax forms are
     identical to `\n'.

   For example,


     .nr a 0 1
     .nr xx 0 5
     .nr foo 0 -2
     \n+a, \n+a, \n+a, \n+a, \n+a
     .br
     \n-(xx, \n-(xx, \n-(xx, \n-(xx, \n-(xx
     .br
     \n+[foo], \n+[foo], \n+[foo], \n+[foo], \n+[foo]

produces


     1, 2, 3, 4, 5
     -5, -10, -15, -20, -25
     -2, -4, -6, -8, -10

   To change the increment value without changing the value of a
register (A in the example), the following can be used:


     .nr a \na 10


File: groff,  Node: Assigning Formats,  Next: Built-in Registers,  Prev: Auto-increment,  Up: Registers

Assigning Formats
-----------------

When a register is used in the text of an input file (as opposed to
part of an expression), it is textually replaced (or interpolated) with
a representation of that number.  This output format can be changed to
a variety of formats (numbers, Roman numerals, etc.).  This is done
using the `af' request.

 - Request: .af ident format
     Change the output format of a number register.  The first argument
     IDENT is the name of the number register to be changed, and the
     second argument FORMAT is the output format.  The following output
     formats are available:

    `1'
          Decimal arabic numbers.  This is the default format: 0, 1, 2,
          3, ....

    `0...0'
          Decimal numbers with as many digits as specified.  So, `00'
          would result in printing numbers as 01, 02, 03, ....

          In fact, any digit instead of zero will do; `gtroff' only
          counts how many digits are specified.  As a consequence,
          `af''s default format `1' could be specified as `0' also (and
          exactly this is returned by the `\g' escape, see below).

    `I'
          Upper-case Roman numerals: 0, I, II, III, IV, ....

    `i'
          Lower-case Roman numerals: 0, i, ii, iii, iv, ....

    `A'
          Upper-case letters: 0, A, B, C, ..., Z, AA, AB, ....

    `a'
          Lower-case letters: 0, a, b, c, ..., z, aa, ab, ....

     Omitting the number register format causes a warning of type
     `missing'.  *Note Debugging::, for more details.  Specifying a
     nonexistent format causes an error.

     The following example produces `10, X, j, 010':


          .nr a 10
          .af a 1           \" the default format
          \na,
          .af a I
          \na,
          .af a a
          \na,
          .af a 001
          \na

     The largest number representable for the `i' and `I' formats is
     39999 (or -39999); UNIX `troff' uses `z' and `w' to represent
     10000 and 5000 in Roman numerals, and so does `gtroff'.
     Currently, the correct glyphs of Roman numeral five thousand and
     Roman numeral ten thousand (Unicode code points `U+2182' and
     `U+2181', respectively) are not available.

     If IDENT doesn't exist, it is created.

     Changing the output format of a read-only register causes an
     error.  It is necessary to first copy the register's value to a
     writeable register, then apply the `af' request to this other
     register.

 - Escape: \gi
 - Escape: \g(id
 - Escape: \g[ident]
     Return the current format of the specified register IDENT
     (one-character name I, two-character name ID).  For example, `\ga'
     after the previous example would produce the string `000'.  If the
     register hasn't been defined yet, nothing is returned.


File: groff,  Node: Built-in Registers,  Prev: Assigning Formats,  Up: Registers

Built-in Registers
------------------

The following lists some built-in registers which are not described
elsewhere in this manual.  Any register which begins with a `.' is
read-only.  A complete listing of all built-in registers can be found in
*Note Register Index::.

`\n[.F]'
     This string-valued register returns the current input file name.

`\n[.H]'
     Horizontal resolution in basic units.

`\n[.U]'
     If `gtroff' is called with the `-U' command line option, the
     number register `.U' is set to 1, and zero otherwise.  *Note Groff
     Options::.

`\n[.V]'
     Vertical resolution in basic units.

`\n[seconds]'
     The number of seconds after the minute, normally in the range 0
     to 59, but can be up to 61 to allow for leap seconds.  Initialized
     at start-up of `gtroff'.

`\n[minutes]'
     The number of minutes after the hour, in the range 0 to 59.
     Initialized at start-up of `gtroff'.

`\n[hours]'
     The number of hours past midnight, in the range 0 to 23.
     Initialized at start-up of `gtroff'.

`\n[dw]'
     Day of the week (1-7).

`\n[dy]'
     Day of the month (1-31).

`\n[mo]'
     Current month (1-12).

`\n[year]'
     The current year.

`\n[yr]'
     The current year minus 1900.  Unfortunately, the documentation of
     UNIX Version 7's `troff' had a year 2000 bug: It incorrectly
     claimed that `yr' contains the last two digits of the year.  That
     claim has never been true of either AT&T `troff' or GNU `troff'.
     Old `troff' input that looks like this:


          '\" The following line stopped working after 1999
          This document was formatted in 19\n(yr.

     can be corrected as follows:


          This document was formatted in \n[year].

     or, to be portable to older `troff' versions, as follows:


          .nr y4 1900+\n(yr
          This document was formatted in \n(y4.

`\n[.c]'
`\n[c.]'
     The current _input_ line number.  Register `.c' is read-only,
     whereas `c.' (a `gtroff' extension) is writable also, affecting
     both `.c' and `c.'.

`\n[ln]'
     The current _output_ line number after a call to the `nm' request
     to activate line numbering.

     *Note Miscellaneous::, for more information about line numbering.

`\n[.x]'
     The major version number.  For example, if the version number is
     1.03 then `.x' contains `1'.

`\n[.y]'
     The minor version number.  For example, if the version number is
     1.03 then `.y' contains `03'.

`\n[.Y]'
     The revision number of `groff'.

`\n[$$]'
     The process ID of `gtroff'.

`\n[.g]'
     Always 1.  Macros should use this to determine whether they are
     running under GNU `troff'.

`\n[.A]'
     If the command line option `-a' is used to produce an ASCII
     approximation of the output, this is set to 1, zero otherwise.
     *Note Groff Options::.

`\n[.P]'
     This register is set to 1 (and to 0 otherwise) if the current page
     is actually being printed, i.e., if the `-o' option is being used
     to only print selected pages.  *Note Groff Options::, for more
     information.

`\n[.T]'
     If `gtroff' is called with the `-T' command line option, the
     number register `.T' is set to 1, and zero otherwise.  *Note Groff
     Options::.

`\*[.T]'
     A single read-write string register which contains the current
     output device (for example, `latin1' or `ps').  This is the only
     string register defined by `gtroff'.


File: groff,  Node: Manipulating Filling and Adjusting,  Next: Manipulating Hyphenation,  Prev: Registers,  Up: gtroff Reference

Manipulating Filling and Adjusting
==================================

Various ways of causing "breaks" were given in *Note Implicit Line
Breaks::.  The `br' request likewise causes a break.  Several other
requests also cause breaks, but implicitly.  These are `bp', `ce',
`cf', `fi', `fl', `in', `nf', `rj', `sp', `ti', and `trf'.

 - Request: .br
     Break the current line, i.e., the input collected so far is emitted
     without adjustment.

     If the no-break control character is used, `gtroff' suppresses the
     break:


          a
          'br
          b
              => a b


   Initially, `gtroff' fills and adjusts text to both margins.  Filling
can be disabled via the `nf' request and re-enabled with the `fi'
request.

 - Request: .fi
 - Register: \n[.u]
     Activate fill mode (which is the default).  This request implicitly
     enables adjusting; it also inserts a break in the text currently
     being filled.  The read-only number register `.u' is set to 1.

     The fill mode status is associated with the current environment
     (*note Environments::).

     See *Note Line Control::, for interaction with the `\c' escape.

 - Request: .nf
     Activate no-fill mode.  Input lines are output as-is, retaining
     line breaks and ignoring the current line length.  This command
     implicitly disables adjusting; it also causes a break.  The number
     register `.u' is set to 0.

     The fill mode status is associated with the current environment
     (*note Environments::).

     See *Note Line Control::, for interaction with the `\c' escape.

 - Request: .ad [mode]
 - Register: \n[.j]
     Set adjusting mode.

     Activation and deactivation of adjusting is done implicitly with
     calls to the `fi' or `nf' requests.

     MODE can have one of the following values:

    `l'
          Adjust text to the left margin.  This produces what is
          traditionally called ragged-right text.

    `r'
          Adjust text to the right margin, producing ragged-left text.

    `c'
          Center filled text.  This is different to the `ce' request
          which only centers text without filling.

    `b'
    `n'
          Justify to both margins.  This is the default used by
          `gtroff'.

     Finally, MODE can be the numeric argument returned by the `.j'
     register.

     With no argument, `gtroff' adjusts lines in the same way it did
     before adjusting was deactivated (with a call to `na', for
     example).


          text
          .ad r
          .nr ad \n[.j]
          text
          .ad c
          text
          .na
          text
          .ad         \" back to centering
          text
          .ad \n[ad]  \" back to right justifying

     The current adjustment mode is available in the read-only number
     register `.j'; it can be stored and subsequently used to set
     adjustment.

     The adjustment mode status is associated with the current
     environment (*note Environments::).

 - Request: .na
     Disable adjusting.  This request won't change the current
     adjustment mode: A subsequent call to `ad' uses the previous
     adjustment setting.

     The adjustment mode status is associated with the current
     environment (*note Environments::).

 - Request: .brp
 - Escape: \p
     Adjust the current line and cause a break.

     In most cases this produces very ugly results since `gtroff'
     doesn't have a sophisticated paragraph building algorithm (as TeX
     have, for example); instead, `gtroff' fills and adjusts a paragraph
     line by line:


            This is an uninteresting sentence.
            This is an uninteresting sentence.\p
            This is an uninteresting sentence.

     is formatted as


            This is  an uninteresting  sentence.   This  is an
            uninteresting                            sentence.
            This is an uninteresting sentence.


 - Request: .ss word_space_size [sentence_space_size]
 - Register: \n[.ss]
 - Register: \n[.sss]
     Change the size of a space between words.  It takes its units as
     one twelfth of the space width parameter for the current font.
     Initially both the WORD_SPACE_SIZE and SENTENCE_SPACE_SIZE are 12.
     In fill mode, the values specify the minimum distance.

     If two arguments are given to the `ss' request, the second
     argument sets the sentence space size.  If the second argument is
     not given, sentence space size is set to WORD_SPACE_SIZE.  The
     sentence space size is used in two circumstances: If the end of a
     sentence occurs at the end of a line in fill mode, then both an
     inter-word space and a sentence space are added; if two spaces
     follow the end of a sentence in the middle of a line, then the
     second space is a sentence space.  If a second argument is never
     given to the `ss' request, the behaviour of UNIX `troff' is the
     same as that exhibited by GNU `troff'.  In GNU `troff', as in UNIX
     `troff', a sentence should always be followed by either a newline
     or two spaces.

     The read-only number registers `.ss' and `.sss' hold the values of
     the parameters set by the first and second arguments of the `ss'
     request.

     The word space and sentence space values are associated with the
     current environment (*note Environments::).

     Contrary to AT&T `troff', this request is _not_ ignored if a TTY
     output device is used; the given values are then rounded down to a
     multiple of 12 (*note Implementation Differences::).

     The request is ignored if there is no parameter.

     Another useful application of the `ss' request is to insert
     discardable horizontal space, i.e., space which is discarded at a
     line break.  For example, paragraph-style footnotes could be
     separated this way:


          .ll 4.5i
          1.\ This is the first footnote.\c
          .ss 48
          .nop
          .ss 12
          2.\ This is the second footnote.

     The result:


          1. This is the first footnote.        2. This
          is the second footnote.

     Note that the `\h' escape produces unbreakable space.

 - Request: .ce [nnn]
 - Register: \n[.ce]
     Center text.  While the `.ad c' request also centers text, it
     fills the text as well.  `ce' does not fill the text it affects.
     This request causes a break.  The number of lines still to be
     centered is associated with the current environment (*note
     Environments::).

     The following example demonstrates the differences.  Here the
     input:


          .ll 4i
          .ce 1000
          This is a small text fragment which shows the differences
          between the `.ce' and the `.ad c' request.
          .ce 0
          
          .ad c
          This is a small text fragment which shows the differences
          between the `.ce' and the `.ad c' request.

     And here the result:


            This is a small text fragment which
                   shows the differences
          between the `.ce' and the `.ad c' request.
          
            This is a small text fragment which
          shows the differences between the `.ce'
                  and the `.ad c' request.

     With no arguments, `ce' centers the next line of text.  NNN
     specifies the number of lines to be centered.  If the argument is
     zero or negative, centering is disabled.

     The basic length for centering text is the line length (as set
     with the `ll' request) minus the indentation (as set with the `in'
     request).  Temporary indentation is ignored.

     As can be seen in the previous example, it is a common idiom to
     turn on centering for a large number of lines, and to turn off
     centering after text to be centered.  This is useful for any
     request which takes a number of lines as an argument.

     The `.ce' read-only number register contains the number of lines
     remaining to be centered, as set by the `ce' request.

 - Request: .rj [nnn]
 - Register: \n[.rj]
     Justify unfilled text to the right margin.  Arguments are
     identical to the `ce' request.  The `.rj' read-only number
     register is the number of lines to be right-justified as set by
     the `rj' request.  This request causes a break.  The number of
     lines still to be right-justified is associated with the current
     environment (*note Environments::).


File: groff,  Node: Manipulating Hyphenation,  Next: Manipulating Spacing,  Prev: Manipulating Filling and Adjusting,  Up: gtroff Reference

Manipulating Hyphenation
========================

As discussed in *Note Hyphenation::, `gtroff' hyphenates words.  There
are a number of ways to influence hyphenation.

 - Request: .hy [mode]
 - Register: \n[.hy]
     Enable hyphenation.  The request has an optional numeric argument,
     MODE, to restrict hyphenation if necessary:

    `1'
          The default argument if MODE is omitted.  Hyphenate without
          restrictions.  This is also the start-up value of `gtroff'.

    `2'
          Do not hyphenate the last word on a page or column.

    `4'
          Do not hyphenate the last two characters of a word.

    `8'
          Do not hyphenate the first two characters of a word.

     Values in the previous table are additive.  For example, the
     value 12 causes `gtroff' to neither hyphenate the last two nor the
     first two characters of a word.

     The current hyphenation restrictions can be found in the read-only
     number register `.hy'.

     The hyphenation mode is associated with the current environment
     (*note Environments::).

 - Request: .nh
     Disable hyphenation (i.e., set the hyphenation mode to zero).  Note
     that the hyphenation mode of the last call to `hy' is not
     remembered.

     The hyphenation mode is associated with the current environment
     (*note Environments::).

 - Request: .hlm [nnn]
 - Register: \n[.hlm]
 - Register: \n[.hlc]
     Set the maximum number of consecutive hyphenated lines to NNN.  If
     this number is negative, there is no maximum.  The default value
     is -1 if NNN is omitted.  This value is associated with the
     current environment (*note Environments::).  Only lines output
     from a given environment count towards the maximum associated with
     that environment.  Hyphens resulting from `\%' are counted;
     explicit hyphens are not.

     The current setting of `hlm' is available in the `.hlm' read-only
     number register.  Also the number of immediately preceding
     consecutive hyphenated lines are available in the read-only number
     register `.hlc'.

 - Request: .hw word1 word2 ...
     Define how WORD1, WORD2, etc. are to be hyphenated.  The words
     must be given with hyphens at the hyphenation points.  For example:


          .hw in-sa-lub-rious

     Besides the space character, any character whose hyphenation code
     value is zero can be used to separate the arguments of `hw' (see
     the documentation for the `hcode' request below for more
     information).  In addition, this request can be used more than
     once.

     Hyphenation exceptions specified with the `hw' request are
     associated with the current hyphenation language; it causes an
     error if there is no current hyphenation language.

     This request is ignored if there is no parameter.

     In old versions of `troff' there was a limited amount of space to
     store such information; fortunately, with `gtroff', this is no
     longer a restriction.

 - Escape: \%
 - Escape: \:
     To tell `gtroff' how to hyphenate words on the fly, use the `\%'
     escape, also known as the "hyphenation character".  Preceding a
     word with this character prevents it from being hyphenated;
     putting it inside a word indicates to `gtroff' that the word may
     be hyphenated at that point.  Note that this mechanism only
     affects that one occurrence of the word; to change the hyphenation
     of a word for the entire document, use the `hw' request.

     The `\:' escape inserts a zero-width break point (that is, the
     word breaks but without adding a hyphen).


          ... check the /var/log/\:httpd/\:access_log file ...

     Note that `\X' and `\Y' start a word, that is, the `\%' escape in
     (say) `\X'...'\%foobar' and `\Y'...'\%foobar' no longer prevents
     hyphenation but inserts a hyphenation point at the beginning of
     `foobar'; most likely this isn't what you want to do.

 - Request: .hc [char]
     Change the hyphenation character to CHAR.  This character then
     works the same as the `\%' escape, and thus, no longer appears in
     the output.  Without an argument, `hc' resets the hyphenation
     character to be `\%' (the default) only.

     The hyphenation character is associated with the current
     environment (*note Environments::).

 - Request: .hpf pattern_file
 - Request: .hpfa pattern_file
 - Request: .hpfcode a b [c d ...]
     Read in a file of hyphenation patterns.  This file is searched for
     in the same way as `NAME.tmac' (or `tmac.NAME') is searched for if
     the `-mNAME' option is specified.

     It should have the same format as (simple) TeX patterns files.
     More specifically, the following scanning rules are implemented.

        * A percent sign starts a comment (up to the end of the line)
          even if preceded by a backslash.

        * No support for `digraphs' like `\$'.

        * `^^XX' (X is 0-9 or a-f) and `^^X' (character code of X in
          the range 0-127) are recognized; other use of `^' causes an
          error.

        * No macro expansion.

        * `hpf' checks for the expression `\patterns{...}' (possibly
          with whitespace before and after the braces).  Everything
          between the braces is taken as hyphenation patterns.
          Consequently, `{' and `}' are not allowed in patterns.

        * Similarly, `\hyphenation{...}' gives a list of hyphenation
          exceptions.

        * `\endinput' is recognized also.

        * For backwards compatibility, if `\patterns' is missing, the
          whole file is treated as a list of hyphenation patterns (only
          recognizing the `%' character as the start of a comment).

     If no `hpf' request is specified (either in the document or in a
     macro package), `gtroff' won't hyphenate at all.

     The `hpfa' request appends a file of patterns to the current list.

     The `hpfcode' request defines mapping values for character codes in
     hyphenation patterns.  `hpf' or `hpfa' then apply the mapping
     (after reading the patterns) before replacing or appending them to
     the current list of patterns.  Its arguments are pairs of
     character codes - integers from 0 to 255.  The request maps
     character code A to code B, code C to code D, and so on.  You can
     use character codes which would be invalid otherwise.

     The set of hyphenation patterns is associated with the current
     language set by the `hla' request.  The `hpf' request is usually
     invoked by the `troffrc' or `troffrc-end' file; by default,
     `troffrc' loads hyphenation patterns and exceptions for American
     English (in files `hyphen.us' and `hyphenex.us').

     A second call to `hpf' (for the same language) will replace the
     hyphenation patterns with the new ones.

     Invoking `hpf' causes an error if there is no current hyphenation
     language.

 - Request: .hcode c1 code1 c2 code2 ...
     Set the hyphenation code of character C1 to CODE1, that of C2 to
     CODE2, etc.  A hyphenation code must be a single input character
     (not a special character) other than a digit or a space.
     Initially each lower-case letter (`a'-`z') has its hyphenation
     code set to itself, and each upper-case letter (`A'-`Z') has a
     hyphenation code which is the lower-case version of itself.

     This request is ignored if it has no parameter.

 - Request: .hym [length]
 - Register: \n[.hym]
     Set the (right) hyphenation margin to LENGTH.  If the current
     adjustment mode is not `b' or `n', the line is not hyphenated if
     it is shorter than LENGTH.  Without an argument, the hyphenation
     margin is reset to its default value, which is 0.  The default
     scaling indicator for this request is `m'.  The hyphenation margin
     is associated with the current environment (*note Environments::).

     A negative argument resets the hyphenation margin to zero, emitting
     a warning of type `range'.

     The current hyphenation margin is available in the `.hym' read-only
     number register.

 - Request: .hys [hyphenation_space]
 - Register: \n[.hys]
     Set the hyphenation space to HYPHENATION_SPACE.  If the current
     adjustment mode is `b' or `n', don't hyphenate the line if it can
     be justified by adding no more than HYPHENATION_SPACE extra space
     to each word space.  Without argument, the hyphenation space is
     set to its default value, which is 0.  The default scaling
     indicator for this request is `m'.  The hyphenation space is
     associated with the current environment (*note Environments::).

     A negative argument resets the hyphenation space to zero, emitting
     a warning of type `range'.

     The current hyphenation space is available in the `.hys' read-only
     number register.

 - Request: .shc [glyph]
     Set the "soft hyphen character" to GLYPH.(1) (*note Manipulating
     Hyphenation-Footnote-1::)  If the argument is omitted, the soft
     hyphen character is set to the default glyph `\(hy' (this is the
     start-up value of `gtroff' also).  The soft hyphen character is
     the glyph that is inserted when a word is hyphenated at a line
     break.  If the soft hyphen character does not exist in the font of
     the character immediately preceding a potential break point, then
     the line is not broken at that point.  Neither definitions
     (specified with the `char' request) nor translations (specified
     with the `tr' request) are considered when finding the soft hyphen
     character.

 - Request: .hla language
 - Register: \n[.hla]
     Set the current hyphenation language to the string LANGUAGE.
     Hyphenation exceptions specified with the `hw' request and
     hyphenation patterns specified with the `hpf' and `hpfa' requests
     are both associated with the current hyphenation language.  The
     `hla' request is usually invoked by the `troffrc' or the
     `troffrc-end' files; `troffrc' sets the default language to `us'.

     The current hyphenation language is available as a string in the
     read-only number register `.hla'.


          .ds curr_language \n[.hla]
          \*[curr_language]
              => us



File: groff,  Node: Manipulating Hyphenation-Footnotes,  Up: Manipulating Hyphenation

   (1) "Soft hyphen character" is a misnomer since it is an output
glyph.


File: groff,  Node: Manipulating Spacing,  Next: Tabs and Fields,  Prev: Manipulating Hyphenation,  Up: gtroff Reference

Manipulating Spacing
====================

 - Request: .sp [distance]
     Space downwards DISTANCE.  With no argument it advances 1 line.  A
     negative argument causes `gtroff' to move up the page the
     specified distance.  If the argument is preceded by a `|' then
     `gtroff' moves that distance from the top of the page.  This
     request causes a line break.  The default scaling indicator is `v'.

     If a vertical trap is sprung during execution of `sp', the amount
     of vertical space after the trap is discarded.  For example, this


          .de xxx
          ..
          .
          .wh 0 xxx
          .
          .pl 5v
          foo
          .sp 2
          bar
          .sp 50
          baz

     results in


          foo
          
          
          bar
          
          baz

     The amount of discarded space is available in the number register
     `.trunc'.

     To protect `sp' against vertical traps, use the `vpt' request:


          .vpt 0
          .sp -3
          .vpt 1


 - Request: .ls [nnn]
 - Register: \n[.L]
     Output NNN-1 blank lines after each line of text.  With no
     argument, `gtroff' uses the previous value before the last `ls'
     call.


          .ls 2    \" This causes double-spaced output
          .ls 3    \" This causes triple-spaced output
          .ls      \" Again double-spaced

     The line spacing is associated with the current environment (*note
     Environments::).

     The read-only number register `.L' contains the current line
     spacing setting.

   *Note Changing Type Sizes::, for the requests `vs' and `pvs' as
alternatives to `ls'.

 - Escape: \x'spacing'
 - Register: \n[.a]
     Sometimes, extra vertical spacing is only needed occasionally, e.g.
     to allow space for a tall construct (like an equation).  The `\x'
     escape does this.  The escape is given a numerical argument,
     usually enclosed in quotes (like `\x'3p''); the default scaling
     indicator is `v'.  If this number is positive extra vertical space
     is inserted below the current line.  A negative number adds space
     above.  If this escape is used multiple times on the same line,
     the maximum of the values is used.

     *Note Escapes::, for details on parameter delimiting characters.

     The `.a' read-only number register contains the most recent
     (nonnegative) extra vertical line space.

     Using `\x' can be necessary in combination with the `\b' escape,
     as the following example shows.


          This is a test with the \[rs]b escape.
          .br
          This is a test with the \[rs]b escape.
          .br
          This is a test with \b'xyz'\x'-1m'\x'1m'.
          .br
          This is a test with the \[rs]b escape.
          .br
          This is a test with the \[rs]b escape.

     produces


          This is a test with the \b escape.
          This is a test with the \b escape.
                              x
          This is a test with y.
                              z
          This is a test with the \b escape.
          This is a test with the \b escape.


 - Request: .ns
 - Request: .rs
 - Register: \n[.ns]
     Enable "no-space mode".  In this mode, spacing (either via `sp' or
     via blank lines) is disabled.  The `bp' request to advance to the
     next page is also disabled, except if it is accompanied by a page
     number (see *Note Page Control::, for more information).  This
     mode ends when actual text is output or the `rs' request is
     encountered which ends no-space mode.  The read-only number
     register `.ns' is set to 1 as long as no-space mode is active.

     This request is useful for macros that conditionally insert
     vertical space before the text starts (for example, a paragraph
     macro could insert some space except when it is the first
     paragraph after a section header).


File: groff,  Node: Tabs and Fields,  Next: Character Translations,  Prev: Manipulating Spacing,  Up: gtroff Reference

Tabs and Fields
===============

A tab character (ASCII char 9, EBCDIC char 5) causes a horizontal
movement to the next tab stop (much like it did on a typewriter).

 - Escape: \t
     This escape is a non-interpreted tab character.  In copy mode
     (*note Copy-in Mode::), `\t' is the same as a real tab character.

 - Request: .ta [n1 n2 ... nn T r1 r2 ... rn]
 - Register: \n[.tabs]
     Change tab stop positions.  This request takes a series of tab
     specifiers as arguments (optionally divided into two groups with
     the letter `T') which indicate where each tab stop is to be
     (overriding any previous settings).

     Tab stops can be specified absolutely, i.e., as the distance from
     the left margin.  For example, the following sets 6 tab stops every
     one inch.


          .ta 1i 2i 3i 4i 5i 6i

     Tab stops can also be specified using a leading `+' which means
     that the specified tab stop is set relative to the previous tab
     stop.  For example, the following is equivalent to the previous
     example.


          .ta 1i +1i +1i +1i +1i +1i

     `gtroff' supports an extended syntax to specify repeat values after
     the `T' mark (these values are always taken as relative) - this is
     the usual way to specify tabs set at equal intervals.  The
     following is, yet again, the same as the previous examples.  It
     does even more since it defines an infinite number of tab stops
     separated by one inch.


          .ta T 1i

     Now we are ready to interpret the full syntax given at the
     beginning: Set tabs at positions N1, N2, ..., NN and then set tabs
     at NN+R1, NN+R2, ..., NN+RN and then at NN+RN+R1, NN+RN+R2, ...,
     NN+RN+RN, and so on.

     Example: `4c +6c T 3c 5c 2c' is equivalent to `4c 10c 13c 18c 20c
     23c 28c 30c ...'.

     The material in each tab column (i.e., the column between two tab
     stops) may be justified to the right or left or centered in the
     column.  This is specified by appending `R', `L', or `C' to the tab
     specifier.  The default justification is `L'.  Example:


          .ta 1i 2iC 3iR

     Some notes:

        * The default unit of the `ta' request is `m'.

        * A tab stop is converted into a non-breakable horizontal
          movement which can be neither stretched nor squeezed.  For
          example,


               .ds foo a\tb\tc
               .ta T 5i
               \*[foo]

          creates a single line which is a bit longer than 10 inches (a
          string is used to show exactly where the tab characters are).
          Now consider the following:


               .ds bar a\tb b\tc
               .ta T 5i
               \*[bar]

          `gtroff' first converts the tab stops of the line into
          unbreakable horizontal movements, then splits the line after
          the second `b' (assuming a sufficiently short line length).
          Usually, this isn't what the user wants.

        * Superfluous tabs (i.e., tab characters which do not
          correspond to a tab stop) are ignored except the first one
          which delimits the characters belonging to the last tab stop
          for right-justifying or centering.  Consider the following
          example


               .ds Z   foo\tbar\tfoo
               .ds ZZ  foo\tbar\tfoobar
               .ds ZZZ foo\tbar\tfoo\tbar
               .ta 2i 4iR
               \*[Z]
               .br
               \*[ZZ]
               .br
               \*[ZZZ]
               .br

          which produces the following output:


               foo                 bar              foo
               foo                 bar           foobar
               foo                 bar              foobar

          The first line right-justifies the second `foo' relative to
          the tab stop.  The second line right-justifies `foobar'.  The
          third line finally right-justifies only `foo' because of the
          additional tab character which marks the end of the string
          belonging to the last defined tab stop.

        * Tab stops are associated with the current environment (*note
          Environments::).

        * Calling `ta' without an argument removes all tab stops.

        * The start-up value of `gtroff' is `T 0.8i'.

     The read-only number register `.tabs' contains a string
     representation of the current tab settings suitable for use as an
     argument to the `ta' request.


          .ds tab-string \n[.tabs]
          \*[tab-string]
              => T120u

     The `troff' version of the Plan 9 operating system uses register
     `.S' for the same purpose.

 - Request: .tc [fill-glyph]
     Normally `gtroff' fills the space to the next tab stop with
     whitespace.  This can be changed with the `tc' request.  With no
     argument `gtroff' reverts to using whitespace, which is the
     default.  The value of this "tab repetition character" is
     associated with the current environment (*note Environments::).(1)
     (*note Tabs and Fields-Footnote-1::)

 - Request: .linetabs n
 - Register: \n[.linetabs]
     If N is missing or not zero, enable "line-tabs" mode, or disable
     it otherwise (the default).  In line-tabs mode, `gtroff' computes
     tab distances relative to the (current) output line instead of the
     input line.

     For example, the following code:


          .ds x a\t\c
          .ds y b\t\c
          .ds z c
          .ta 1i 3i
          \*x
          \*y
          \*z

     in normal mode, results in the output


          a         b         c

     in line-tabs mode, the same code outputs


          a         b                   c

     Line-tabs mode is associated with the current environment.  The
     read-only register `.linetabs' is set to 1 if in line-tabs mode,
     and 0 in normal mode.

* Menu:

* Leaders::
* Fields::


File: groff,  Node: Tabs and Fields-Footnotes,  Up: Tabs and Fields

   (1) "Tab repetition character" is a misnomer since it is an output
glyph.


File: groff,  Node: Leaders,  Next: Fields,  Prev: Tabs and Fields,  Up: Tabs and Fields

Leaders
-------

Sometimes it may may be desirable to use the `tc' request to fill a
particular tab stop with a given glyph (for example dots in a table of
contents), but also normal tab stops on the rest of the line.  For this
`gtroff' provides an alternate tab mechanism, called "leaders" which
does just that.

   A leader character (character code 1) behaves similarly to a tab
character: It moves to the next tab stop.  The only difference is that
for this movement, the fill glyph defaults to a period character and
not to space.

 - Escape: \a
     This escape is a non-interpreted leader character.  In copy mode
     (*note Copy-in Mode::), `\a' is the same as a real leader
     character.

 - Request: .lc [fill-glyph]
     Declare the "leader repetition character".(1) (*note
     Leaders-Footnote-1::) Without an argument, leaders act the same as
     tabs (i.e., using whitespace for filling).  `gtroff''s start-up
     value is a dot (`.').  The value of the leader repetition
     character is associated with the current environment (*note
     Environments::).

   For a table of contents, to name an example, tab stops may be
defined so that the section number is one tab stop, the title is the
second with the remaining space being filled with a line of dots, and
then the page number slightly separated from the dots.


     .ds entry 1.1\tFoo\a\t12
     .lc .
     .ta 1i 5i +.25i
     \*[entry]

This produces


     1.1  Foo..........................................  12


File: groff,  Node: Leaders-Footnotes,  Up: Leaders

   (1) "Leader repetition character" is a misnomer since it is an
output glyph.


File: groff,  Node: Fields,  Prev: Leaders,  Up: Tabs and Fields

Fields
------

"Fields" are a more general way of laying out tabular data.  A field is
defined as the data between a pair of "delimiting characters".  It
contains substrings which are separated by "padding characters".  The
width of a field is the distance on the _input_ line from the position
where the field starts to the next tab stop.  A padding character
inserts stretchable space similar to TeX's `\hss' command (thus it can
even be negative) to make the sum of all substring lengths plus the
stretchable space equal to the field width.  If more than one padding
character is inserted, the available space is evenly distributed among
them.

 - Request: .fc [delim-char [padding-char]]
     Define a delimiting and a padding character for fields.  If the
     latter is missing, the padding character defaults to a space
     character.  If there is no argument at all, the field mechanism is
     disabled (which is the default).  Note that contrary to e.g. the
     tab repetition character, delimiting and padding characters are
     _not_ associated to the current environment (*note Environments::).

     Example:


          .fc # ^
          .ta T 3i
          #foo^bar^smurf#
          .br
          #foo^^bar^smurf#

     and here the result:


          foo         bar          smurf
          foo            bar       smurf



File: groff,  Node: Character Translations,  Next: Troff and Nroff Mode,  Prev: Tabs and Fields,  Up: gtroff Reference

Character Translations
======================

The control character (`.') and the no-break control character (`'')
can be changed with the `cc' and `c2' requests, respectively.

 - Request: .cc [c]
     Set the control character to C.  With no argument the default
     control character `.' is restored.  The value of the control
     character is associated with the current environment (*note
     Environments::).

 - Request: .c2 [c]
     Set the no-break control character to C.  With no argument the
     default control character `'' is restored.  The value of the
     no-break control character is associated with the current
     environment (*note Environments::).

 - Request: .eo
     Disable the escape mechanism completely.  After executing this
     request, the backslash character `\' no longer starts an escape
     sequence.

     This request can be very helpful in writing macros since it is not
     necessary then to double the escape character.  Here an example:


          .\" This is a simplified version of the
          .\" .BR request from the man macro package
          .eo
          .de BR
          .  ds result \&
          .  while (\n[.$] >= 2) \{\
          .    as result \fB\$1\fR\$2
          .    shift 2
          .  \}
          .  if \n[.$] .as result \fB\$1
          \*[result]
          .  ft R
          ..
          .ec


 - Request: .ec [c]
     Set the escape character to C.  With no argument the default
     escape character `\' is restored.  It can be also used to
     re-enable the escape mechanism after an `eo' request.

     Note that changing the escape character globally will likely break
     macro packages since `gtroff' has no mechanism to `intern' macros,
     i.e., to convert a macro definition into an internal form which is
     independent of its representation (TeX has this mechanism).  If a
     macro is called, it is executed literally.

 - Request: .ecs
 - Request: .ecr
     The `ecs' request saves the current escape character in an
     internal register.  Use this request in combination with the `ec'
     request to temporarily change the escape character.

     The `ecr' request restores the escape character saved with `ecs'.
     Without a previous call to `ecs', this request sets the escape
     character to `\'.

 - Escape: \\
 - Escape: \e
 - Escape: \E
     Print the current escape character (which is the backslash
     character `\' by default).

     `\\' is a `delayed' backslash; more precisely, it is the default
     escape character followed by a backslash, which no longer has
     special meaning due to the leading escape character.  It is _not_
     an escape sequence in the usual sense!  In any unknown escape
     sequence `\X' the escape character is ignored and X is printed.
     But if X is equal to the current escape character, no warning is
     emitted.

     As a consequence, only at top-level or in a diversion a backslash
     glyph is printed; in copy-in mode, it expands to a single
     backslash which then combines with the following character to an
     escape sequence.

     The `\E' escape differs from `\e' by printing an escape character
     that is not interpreted in copy mode.  Use this to define strings
     with escapes that work when used in copy mode (for example, as a
     macro argument).  The following example defines strings to begin
     and end a superscript:


          .ds { \v'-.3m'\s'\En[.s]*60/100'
          .ds } \s0\v'.3m'

     Another example to demonstrate the differences between the various
     escape sequences, using a strange escape character, `-'.


          .ec -
          .de xxx
          --A'123'
          ..
          .xxx
              => -A'foo'

     The result is surprising for most users, expecting `1' since `foo'
     is a valid identifier.  What has happened?  As mentioned above,
     the leading escape character makes the following character
     ordinary.  Written with the default escape character the sequence
     `--' becomes `\-' - this is the minus sign.

     If the escape character followed by itself is a valid escape
     sequence, only `\E' yields the expected result:


          .ec -
          .de xxx
          -EA'123'
          ..
          .xxx
              => 1


 - Escape: \.
     Similar to `\\', the sequence `\.' isn't a real escape sequence.
     As before, a warning message is suppressed if the escape character
     is followed by a dot, and the dot itself is printed.


          .de foo
          .  nop foo
          .
          .  de bar
          .    nop bar
          \\..
          .
          ..
          .foo
          .bar
              => foo bar

     The first backslash is consumed while the macro is read, and the
     second is swallowed while exexuting macro `foo'.

   A "translation" is a mapping of an input character to an output
glyph.  The mapping occurs at output time, i.e., the input character
gets assigned the metric information of the mapped output character
right before input tokens are converted to nodes (*note Gtroff
Internals::, for more on this process).

 - Request: .tr abcd...
 - Request: .trin abcd...
     Translate character A to glyph B, character C to glyph D, etc.  If
     there is an odd number of arguments, the last one is translated to
     an unstretchable space (`\ ').

     The `trin' request is identical to `tr', but when you unformat a
     diversion with `asciify' it ignores the translation.  *Note
     Diversions::, for details about the `asciify' request.

     Some notes:

        * Special characters (`\(XX', `\[XXX]', `\C'XXX'', `\'', `\`',
          `\-', `\_'), glyphs defined with the `char' request, and
          numbered glyphs (`\N'XXX'') can be translated also.

        * The `\e' escape can be translated also.

        * Characters can be mapped onto the `\%' and `\~' escapes (but
          `\%' and `\~' can't be mapped onto another glyph).

        * The following characters can't be translated: space (with one
          exception, see below), backspace, newline, leader (and `\a'),
          tab (and `\t').

        * Translations are not considered for finding the soft hyphen
          character set with the `shc' request.

        * The pair `C\&' (this is an arbitrary character C followed by
          the zero width space character) maps this character to
          nothing.


               .tr a\&
               foo bar
                   => foo br

          It is even possible to map the space character to nothing:


               .tr aa \&
               foo bar
                   => foobar

          As shown in the example, the space character can't be the
          first character/glyph pair as an argument of `tr'.
          Additionally, it is not possible to map the space character
          to any other glyph; requests like `.tr aa x' undo `.tr aa \&'
          instead.

          If justification is active, lines are justified in spite of
          the `empty' space character (but there is no minimal
          distance, i.e. the space character, between words).

        * After an output glyph has been constructed (this happens at
          the moment immediately before the glyph is appended to an
          output glyph list, either by direct output, in a macro,
          diversion, or string), it is no longer affected by `tr'.

        * Translating character to glyphs where one of them or both are
          undefined is possible also; `tr' does not check whether the
          entities in its argument do exist.

          *Note Gtroff Internals::.

        * `troff' no longer has a hard-coded dependency on Latin-1; all
          `charXXX' entities have been removed from the font
          description files.  This has a notable consequence which
          shows up in warnings like `can't find character with input
          code XXX' if the `tr' request isn't handled properly.

          Consider the following translation:


               .tr e'E'

          This maps input character `e'' onto glyph `E'', which is
          identical to glyph `char201'.  But this glyph intentionally
          doesn't exist!  Instead, `\[char201]' is treated as an input
          character entity and is by default mapped onto `\['E]', and
          `gtroff' doesn't handle translations of translations.

          The right way to write the above translation is


               .tr e'\['E]

          With other words, the first argument of `tr' should be an
          input character or entity, and the second one a glyph entity.

        * Without an argument, the `tr' request is ignored.

 - Request: .trnt abcd...
     `trnt' is the same as the `tr' request except that the
     translations do not apply to text that is transparently throughput
     into a diversion with `\!'.  *Note Diversions::, for more
     information.

     For example,


          .tr ab
          .di x
          \!.tm a
          .di
          .x

     prints `b' to the standard error stream; if `trnt' is used instead
     of `tr' it prints `a'.


File: groff,  Node: Troff and Nroff Mode,  Next: Line Layout,  Prev: Character Translations,  Up: gtroff Reference

Troff and Nroff Mode
====================

Originally, `nroff' and `troff' were two separate programs, the former
for TTY output, the latter for everything else.  With GNU `troff', both
programs are merged into one executable, sending its output to a device
driver (`grotty' for TTY devices, `grops' for POSTSCRIPT, etc.) which
interprets the intermediate output of `gtroff'.  For UNIX `troff' it
makes sense to talk about "Nroff mode" and "Troff mode" since the
differences are hardcoded.  For GNU `troff', this distinction is not
appropriate because `gtroff' simply takes the information given in the
font files for a particular device without handling requests specially
if a TTY output device is used.

   Usually, a macro package can be used with all output devices.
Nevertheless, it is sometimes necessary to make a distinction between
TTY and non-TTY devices: `gtroff' provides two built-in conditions `n'
and `t' for the `if', `ie', and `while' requests to decide whether
`gtroff' shall behave like `nroff' or like `troff'.

 - Request: .troff
     Make the `t' built-in condition true (and the `n' built-in
     condition false) for `if', `ie', and `while' conditional requests.
     This is the default if `gtroff' (_not_ `groff') is started with
     the `-R' switch to avoid loading of the start-up files `troffrc'
     and `troffrc-end'.  Without `-R', `gtroff' stays in troff mode if
     the output device is not a TTY (e.g. `ps').

 - Request: .nroff
     Make the `n' built-in condition true (and the `t' built-in
     condition false) for `if', `ie', and `while' conditional requests.
     This is the default if `gtroff' uses a TTY output device; the
     code for switching to nroff mode is in the file `tty.tmac' which
     is loaded by the start-up file `troffrc'.

   *Note Conditionals and Loops::, for more details on built-in
conditions.


File: groff,  Node: Line Layout,  Next: Line Control,  Prev: Troff and Nroff Mode,  Up: gtroff Reference

Line Layout
===========

The following drawing shows the dimensions which `gtroff' uses for
placing a line of output onto the page.  They are labeled with the
request which manipulates each dimension.


                     -->| in |<--
                        |<-----------ll------------>|
                   +----+----+----------------------+----+
                   |    :    :                      :    |
                   +----+----+----------------------+----+
                -->| po |<--
                   |<--------paper width---------------->|

These dimensions are:

`po'
     "Page offset" - this is the leftmost position of text on the final
     output, defining the "left margin".

`in'
     "Indentation" - this is the distance from the left margin where
     text is printed.

`ll'
     "Line length" - this is the distance from the left margin to right
     margin.

   A simple demonstration:


     .ll 3i
     This is text without indentation.
     The line length has been set to 3\~inch.
     .in +.5i
     .ll -.5i
     Now the left and right margins are both increased.
     .in
     .ll
     Calling .in and .ll without parameters restore
     the previous values.

   Result:


     This  is text without indenta-
     tion.   The  line  length  has
     been set to 3 inch.
          Now   the  left  and
          right  margins   are
          both increased.
     Calling  .in  and  .ll without
     parameters restore the  previ-
     ous values.

 - Request: .po [offset]
 - Request: .po +offset
 - Request: .po -offset
 - Register: \n[.o]
     Set horizontal page offset to OFFSET (or increment or decrement
     the current value by OFFSET).  Note that this request does not
     cause a break, so changing the page offset in the middle of text
     being filled may not yield the expected result.  The initial value
     is 1i.  For TTY output devices, it is set to 0 in the startup file
     `troffrc'; the default scaling indicator is `m' (and not `v' as
     incorrectly documented in the original UNIX troff manual).

     The current page offset can be found in the read-only number
     register `.o'.

     If `po' is called without an argument, the page offset is reset to
     the previous value before the last call to `po'.


          .po 3i
          \n[.o]
              => 720
          .po -1i
          \n[.o]
              => 480
          .po
          \n[.o]
              => 720


 - Request: .in [indent]
 - Request: .in +indent
 - Request: .in -indent
 - Register: \n[.i]
     Set indentation to INDENT (or increment or decrement the current
     value by INDENT).  This request causes a break.  Initially, there
     is no indentation.

     If `in' is called without an argument, the indentation is reset to
     the previous value before the last call to `in'.  The default
     scaling indicator is `m'.

     The indentation is associated with the current environment (*note
     Environments::).

     If a negative indentation value is specified (which is not
     allowed), `gtroff' emits a warning of type `range' and sets the
     indentation to zero.

     The effect of `in' is delayed until a partially collected line (if
     it exists) is output.  A temporary indent value is reset to zero
     also.

     The current indentation (as set by `in') can be found in the
     read-only number register `.i'.

 - Request: .ti offset
 - Request: .ti +offset
 - Request: .ti -offset
 - Register: \n[.in]
     Temporarily indent the next output line by OFFSET.  If an
     increment or decrement value is specified, adjust the temporary
     indentation relative to the value set by the `in' request.

     This request causes a break; its value is associated with the
     current environment (*note Environments::).  The default scaling
     indicator is `m'.  A call of `ti' without an argument is ignored.

     If the total indentation value is negative (which is not allowed),
     `gtroff' emits a warning of type `range' and sets the temporary
     indentation to zero.  `Total indentation' is either OFFSET if
     specified as an absolute value, or the temporary plus normal
     indentation, if OFFSET is given as a relative value.

     The effect of `ti' is delayed until a partially collected line (if
     it exists) is output.

     The read-only number register `.in' is the indentation that applies
     to the current output line.

     The difference between `.i' and `.in' is that the latter takes
     into account whether a partially collected line still uses the old
     indentation value or a temporary indentation value is active.

 - Request: .ll [length]
 - Request: .ll +length
 - Request: .ll -length
 - Register: \n[.l]
 - Register: \n[.ll]
     Set the line length to LENGTH (or increment or decrement the
     current value by LENGTH).  Initially, the line length is set to
     6.5i.  The effect of `ll' is delayed until a partially collected
     line (if it exists) is output.  The default scaling indicator is
     `m'.

     If `ll' is called without an argument, the line length is reset to
     the previous value before the last call to `ll'.  If a negative
     line length is specified (which is not allowed), `gtroff' emits a
     warning of type `range' and sets the line length to zero.

     The line length is associated with the current environment (*note
     Environments::).

     The current line length (as set by `ll') can be found in the
     read-only number register `.l'.  The read-only number register
     `.ll' is the line length that applies to the current output line.

     Similar to `.i' and `.in', the difference between `.l' and `.ll'
     is that the latter takes into account whether a partially
     collected line still uses the old line length value.


File: groff,  Node: Line Control,  Next: Page Layout,  Prev: Line Layout,  Up: gtroff Reference

Line Control
============

It is important to understand how `gtroff' handles input and output
lines.

   Many escapes use positioning relative to the input line.  For
example, this


     This is a \h'|1.2i'test.
     
     This is a
     \h'|1.2i'test.

produces


     This is a   test.
     
     This is a             test.

   The main usage of this feature is to define macros which act exactly
at the place where called.


     .\" A simple macro to underline a word
     .de underline
     .  nop \\$1\l'|0\[ul]'
     ..

In the above example, `|0' specifies a negative distance from the
current position (at the end of the just emitted argument `\$1') back
to the beginning of the input line.  Thus, the `\l' escape draws a line
from right to left.

   `gtroff' makes a difference between input and output line
continuation; the latter is also called "interrupting" a line.

 - Escape: \<RET>
 - Escape: \c
 - Register: \n[.int]
     Continue a line.  `\<RET>' (this is a backslash at the end of a
     line immediately followed by a newline) works on the input level,
     suppressing the effects of the following newline in the input.


          This is a \
          .test
              => This is a .test

     The `|' operator is also affected.

     `\c' works on the output level.  Anything after this escape on the
     same line is ignored, except `\R' which works as usual.  Anything
     before `\c' on the same line will be appended to the current
     partial output line.  The next non-command line after an
     interrupted line counts as a new input line.

     The visual results depend on whether no-fill mode is active.

        * If no-fill mode is active (using the `nf' request), the next
          input text line after `\c' will be handled as a continuation
          of the same input text line.


               .nf
               This is a \c
               test.
                   => This is a test.

        * If fill mode is active (using the `fi' request), a word
          interrupted with `\c' will be continued with the text on the
          next input text line, without an intervening space.


               This is a te\c
               st.
                   => This is a test.


     Note that an intervening control line which causes a break is
     stronger than `\c', flushing out the current partial line in the
     usual way.

     The `.int' register contains a positive value if the last output
     line was interrupted with `\c'; this is associated with the
     current environment (*note Environments::).


File: groff,  Node: Page Layout,  Next: Page Control,  Prev: Line Control,  Up: gtroff Reference

Page Layout
===========

`gtroff' provides some very primitive operations for controlling page
layout.

 - Request: .pl [length]
 - Request: .pl +length
 - Request: .pl -length
 - Register: \n[.p]
     Set the "page length" to LENGTH (or increment or decrement the
     current value by LENGTH).  This is the length of the physical
     output page.  The default scaling indicator is `v'.

     The current setting can be found in the read-only number register
     `.p'.

     Note that this only specifies the size of the page, not the top and
     bottom margins.  Those are not set by `gtroff' directly.  *Note
     Traps::, for further information on how to do this.

     Negative `pl' values are possible also, but not very useful: No
     trap is sprung, and each line is output on a single page (thus
     suppressing all vertical spacing).

     If no argument or an invalid argument is given, `pl' sets the page
     length to 11i.

   `gtroff' provides several operations which help in setting up top
and bottom titles (or headers and footers).

 - Request: .tl 'left'center'right'
     Print a "title line".  It consists of three parts: a left
     justified portion, a centered portion, and a right justified
     portion.  The argument separator `'' can be replaced with any
     character not occurring in the title line.  The `%' character is
     replaced with the current page number.  This character can be
     changed with the `pc' request (see below).

     Without argument, `tl' is ignored.

     Some notes:

        * A title line is not restricted to the top or bottom of a page.

        * `tl' prints the title line immediately, ignoring a partially
          filled line (which stays untouched).

        * It is not an error to omit closing delimiters.  For example,
          `.tl /foo' is equivalent to `.tl /foo///': It prints a title
          line with the left justified word `foo'; the centered and
          right justfied parts are empty.

        * `tl' accepts the same parameter delimiting characters as the
          `\A' escape; see *Note Escapes::.

 - Request: .lt [length]
 - Request: .lt +length
 - Request: .lt -length
 - Register: \n[.lt]
     The title line is printed using its own line length, which is
     specified (or incremented or decremented) with the `lt' request.
     Initially, the title line length is set to 6.5i.  If a negative
     line length is specified (which is not allowed), `gtroff' emits a
     warning of type `range' and sets the title line length to zero.
     The default scaling indicator is `m'.  If `lt' is called without
     an argument, the title length is reset to the previous value
     before the last call to `lt'.

     The current setting of this is available in the `.lt' read-only
     number register; it is associated with the current environment
     (*note Environments::).

 - Request: .pn page
 - Request: .pn +page
 - Request: .pn -page
 - Register: \n[.pn]
     Change (increase or decrease) the page number of the _next_ page.
     The only argument is the page number; the request is ignored
     without a parameter.

     The read-only number register `.pn' contains the number of the next
     page: either the value set by a `pn' request, or the number of the
     current page plus 1.

 - Request: .pc [char]
     Change the page number character (used by the `tl' request) to a
     different character.  With no argument, this mechanism is disabled.
     Note that this doesn't affect the number register `%'.

   *Note Traps::.


File: groff,  Node: Page Control,  Next: Fonts and Symbols,  Prev: Page Layout,  Up: gtroff Reference

Page Control
============

 - Request: .bp [page]
 - Request: .bp +page
 - Request: .bp -page
 - Register: \n[%]
     Stop processing the current page and move to the next page.  This
     request causes a break.  It can also take an argument to set
     (increase, decrease) the page number of the next page (which
     actually becomes the current page after `bp' has finished).  The
     difference between `bp' and `pn' is that `pn' does not cause a
     break or actually eject a page.  *Note Page Layout::.


          .de newpage                         \" define macro
          'bp                                 \" begin page
          'sp .5i                             \" vertical space
          .tl 'left top'center top'right top' \" title
          'sp .3i                             \" vertical space
          ..                                  \" end macro

     `bp' has no effect if not called within the top-level diversion
     (*note Diversions::).

     The read-write register `%' holds the current page number.

     The number register `.pe' is set to 1 while `bp' is active.  *Note
     Page Location Traps::.

 - Request: .ne [space]
     It is often necessary to force a certain amount of space before a
     new page occurs.  This is most useful to make sure that there is
     not a single "orphan" line left at the bottom of a page.  The `ne'
     request ensures that there is a certain distance, specified by the
     first argument, before the next page is triggered (see *Note
     Traps::, for further information).  The default scaling indicator
     for `ne' is `v'; the default value of SPACE is 1v if no argument
     is given.

     For example, to make sure that no fewer than 2 lines get orphaned,
     do the following before each paragraph:


          .ne 2
          text text text

     `ne' will then automatically cause a page break if there is space
     for one line only.

 - Request: .sv [space]
 - Request: .os
     `sv' is similar to the `ne' request; it reserves the specified
     amount of vertical space.  If the desired amount of space exists
     before the next trap (or the bottom page boundary if no trap is
     set), the space is output immediately (ignoring a partially filled
     line which stays untouched).  If there is not enough space, it is
     stored for later output via the `os' request.  The default value
     is 1v if no argument is given; the default scaling indicator is
     `v'.

     Both `sv' and `os' ignore no-space mode.  While the `sv' request
     allows negative values for SPACE, `os' will ignore them.

 - Register: \n[nl]
     This register contains the current vertical position.  If the
     vertical position is zero and the top of page transition hasn't
     happened yet, `nl' is set to negative value.  `gtroff' itself does
     this at the very beginning of a document before anything has been
     printed, but the main usage is to plant a header trap on a page if
     this page has already started.

     Consider the following:


          .de xxx
          .  sp
          .  tl ''Header''
          .  sp
          ..
          .
          First page.
          .bp
          .wh 0 xxx
          .nr nl (-1)
          Second page.

     Result:


          First page.
          
          ...
          
                                       Header
          
          Second page.
          
          ...

     Without resetting `nl' to a negative value, the just planted trap
     would be active beginning with the _next_ page, not the current
     one.

     *Note Diversions::, for a comparison with the `.h' and `.d'
     registers.


File: groff,  Node: Fonts and Symbols,  Next: Sizes,  Prev: Page Control,  Up: gtroff Reference

Fonts and Symbols
=================

`gtroff' can switch fonts at any point in the text.

   The basic set of fonts is `R', `I', `B', and `BI'.  These are Times
Roman, Italic, Bold, and Bold Italic.  For non-TTY devices, there is
also at least one symbol font which contains various special symbols
(Greek, mathematics).

* Menu:

* Changing Fonts::
* Font Families::
* Font Positions::
* Using Symbols::
* Special Fonts::
* Artificial Fonts::
* Ligatures and Kerning::


File: groff,  Node: Changing Fonts,  Next: Font Families,  Prev: Fonts and Symbols,  Up: Fonts and Symbols

Changing Fonts
--------------

 - Request: .ft [font]
 - Escape: \ff
 - Escape: \f(fn
 - Escape: \f[font]
     The `ft' request and the `\f' escape change the current font to
     FONT (one-character name F, two-character name FN).

     If FONT is a style name (as set with the `sty' request or with the
     `styles' command in the `DESC' file), use it within the current
     font family (as set with the `fam' request, `\F' escape, or with
     the `family' command in the `DESC' file).

     With no argument or using `P' as an argument, `.ft' switches to
     the previous font.  Use `\f[]' to do this with the escape.  The
     old syntax forms `\fP' or `\f[P]' are also supported.

     Fonts are generally specified as upper-case strings, which are
     usually 1 to 4 characters representing an abbreviation or acronym
     of the font name.  This is no limitation, just a convention.

     The example below produces two identical lines.


          eggs, bacon,
          .ft B
          spam
          .ft
          and sausage.
          
          eggs, bacon, \fBspam\fP and sausage.

     Note that `\f' doesn't produce an input token in `gtroff'.  As a
     consequence, it can be used in requests like `mc' (which expects a
     single character as an argument) to change the font on the fly:


          .mc \f[I]x\f[]

     *Note Font Positions::, for an alternative syntax.

 - Request: .ftr f [g]
     Translate font F to font G.  Whenever a font named F is referred
     to in a `\f' escape sequence, or in the `ft', `ul', `bd', `cs',
     `tkf', `special', `fspecial', `fp', or `sty' requests, font G is
     used.  If G is missing or equal to F the translation is undone.


File: groff,  Node: Font Families,  Next: Font Positions,  Prev: Changing Fonts,  Up: Fonts and Symbols

Font Families
-------------

Due to the variety of fonts available, `gtroff' has added the concept
of "font families" and "font styles".  The fonts are specified as the
concatenation of the font family and style.  Specifying a font without
the family part causes `gtroff' to use that style of the current family.

   Currently, fonts for the devices `-Tps', `-Tdvi', and `-Tlbp' are
set up to this mechanism.  By default, `gtroff' uses the Times family
with the four styles `R', `I', `B', and `BI'.

   This way, it is possible to use the basic four fonts and to select a
different font family on the command line (*note Groff Options::).

 - Request: .fam [family]
 - Register: \n[.fam]
 - Escape: \Ff
 - Escape: \F(fm
 - Escape: \F[family]
 - Register: \n[.fn]
     Switch font family to FAMILY (one-character name F, two-character
     name FM).  If no argument is given, switch back to the previous
     font family.  Use `\F[]' to do this with the escape.  Note that
     `\FP' doesn't work; it selects font family `P' instead.

     The value at start-up is `T'.  The current font family is
     available in the read-only number register `.fam' (this is a
     string-valued register); it is associated with the current
     environment.


          spam,
          .fam H    \" helvetica family
          spam,     \" used font is family H + style R = HR
          .ft B     \" family H + style B = font HB
          spam,
          .fam T    \" times family
          spam,     \" used font is family T + style B = TB
          .ft AR    \" font AR (not a style)
          baked beans,
          .ft R     \" family T + style R = font TR
          and spam.

     Note that `\F' doesn't produce an input token in `gtroff'.  As a
     consequence, it can be used in requests like `mc' (which expects a
     single character as an argument) to change the font family on the
     fly:


          .mc \F[P]x\F[]

     The `.fn' register contains the current "real font name" of the
     current font.  This is a string-valued register.  If the current
     font is a style, the value of `\n[.fn]' is the proper
     concatenation of family and style name.

 - Request: .sty n style
     Associate STYLE with font position N.  A font position can be
     associated either with a font or with a style.  The current font
     is the index of a font position and so is also either a font or a
     style.  If it is a style, the font that is actually used is the
     font which name is the concatenation of the name of the current
     family and the name of the current style.  For example, if the
     current font is 1 and font position 1 is associated with style `R'
     and the current font family is `T', then font `TR' will be used.
     If the current font is not a style, then the current family is
     ignored.  If the requests `cs', `bd', `tkf', `uf', or `fspecial'
     are applied to a style, they will instead be applied to the member
     of the current family corresponding to that style.

     N must be a non-negative integer value.

     The default family can be set with the `-f' option (*note Groff
     Options::).  The `styles' command in the `DESC' file controls
     which font positions (if any) are initially associated with styles
     rather than fonts.  For example, the default setting for
     POSTSCRIPT fonts


          styles R I B BI

     is equivalent to


          .sty 1 R
          .sty 2 I
          .sty 3 B
          .sty 4 BI

     `fam' and `\F' always check whether the current font position is
     valid; this can give surprising results if the current font
     position is associated with a style.

     In the following example, we want to access the POSTSCRIPT font
     `FooBar' from the font family `Foo':


          .sty \n[.fp] Bar
          .fam Foo
              => warning: can't find font `FooR'

     The default font position at start-up is 1; for the POSTSCRIPT
     device, this is associated with style `R', so `gtroff' tries to
     open `FooR'.

     A solution to this problem is to use a dummy font like the
     following:


          .fp 0 dummy TR    \" set up dummy font at position 0
          .sty \n[.fp] Bar  \" register style `Bar'
          .ft 0             \" switch to font at position 0
          .fam Foo          \" activate family `Foo'
          .ft Bar           \" switch to font `FooBar'

     *Note Font Positions::.


File: groff,  Node: Font Positions,  Next: Using Symbols,  Prev: Font Families,  Up: Fonts and Symbols

Font Positions
--------------

For the sake of old phototypesetters and compatibility with old versions
of `troff', `gtroff' has the concept of font "positions", on which
various fonts are mounted.

 - Request: .fp pos font [external-name]
 - Register: \n[.f]
 - Register: \n[.fp]
     Mount font FONT at position POS (which must be a non-negative
     integer).  This numeric position can then be referred to with font
     changing commands.  When `gtroff' starts it is using font
     position 1 (which must exist; position 0 is unused usually at
     start-up).

     The current font in use, as a font position, is available in the
     read-only number register `.f'.  This can be useful to remember the
     current font for later recall.  It is associated with the current
     environment (*note Environments::).


          .nr save-font \n[.f]
          .ft B
          ... text text text ...
          .ft \n[save-font]

     The number of the next free font position is available in the
     read-only number register `.fp'.  This is useful when mounting a
     new font, like so:


          .fp \n[.fp] NEATOFONT

     Fonts not listed in the `DESC' file are automatically mounted on
     the next available font position when they are referenced.  If a
     font is to be mounted explicitly with the `fp' request on an unused
     font position, it should be mounted on the first unused font
     position, which can be found in the `.fp' register.  Although
     `gtroff' does not enforce this strictly, it is not allowed to
     mount a font at a position whose number is much greater (approx.
     1000 positions) than that of any currently used position.

     The `fp' request has an optional third argument.  This argument
     gives the external name of the font, which is used for finding the
     font description file.  The second argument gives the internal
     name of the font which is used to refer to the font in `gtroff'
     after it has been mounted.  If there is no third argument then the
     internal name is used as the external name.  This feature makes it
     possible to use fonts with long names in compatibility mode.

   Both the `ft' request and the `\f' escape have alternative syntax
forms to access font positions.

 - Request: .ft nnn
 - Escape: \fn
 - Escape: \f(nn
 - Escape: \f[nnn]
     Change the current font position to NNN (one-digit position N,
     two-digit position NN), which must be a non-negative integer.

     If NNN is associated with a style (as set with the `sty' request
     or with the `styles' command in the `DESC' file), use it within
     the current font family (as set with the `fam' request, the `\F'
     escape, or with the `family' command in the `DESC' file).


          this is font 1
          .ft 2
          this is font 2
          .ft                   \" switch back to font 1
          .ft 3
          this is font 3
          .ft
          this is font 1 again

     *Note Changing Fonts::, for the standard syntax form.


File: groff,  Node: Using Symbols,  Next: Special Fonts,  Prev: Font Positions,  Up: Fonts and Symbols

Using Symbols
-------------

A "glyph" is a graphical representation of a "character".  While a
character is an abstract entity containing semantic information, a
glyph is something which can be actually seen on screen or paper.  It
is possible that a character has multiple glyph representation forms
(for example, the character `A' can be either written in a roman or an
italic font, yielding two different glyphs); sometimes more than one
character maps to a single glyph (this is a "ligature" - the most
common is `fi').

   A "symbol" is simply a named glyph.  Within `gtroff', all glyph
names of a particular font are defined in its font file.  If the user
requests a glyph not available in this font, `gtroff' looks up an
ordered list of "special fonts".  By default, the POSTSCRIPT output
device supports the two special fonts `SS' (slanted symbols) and `S'
(symbols) (the former is looked up before the latter).  Other output
devices use different names for special fonts.  Fonts mounted with the
`fonts' keyword in the `DESC' file are globally available.  To install
additional special fonts locally (i.e. for a particular font), use the
`fspecial' request.

   Here the exact rules how `gtroff' searches a given symbol:

   * If the symbol has been defined with the `char' request, use it.
     This hides a symbol with the same name in the current font.

   * Check the current font.

   * If the symbol has been defined with the `fchar' request, use it.

   * Check whether the current font has a font-specific list of special
     fonts; test all fonts in the order of appearance in the last
     `fspecial' call if appropriate.

   * If the symbol has been defined with the `fschar' request for the
     current font, use it.

   * Check all fonts in the order of appearance in the last `special'
     call.

   * If the symbol has been defined with the `schar' request, use it.

   * As a last resort, consult all fonts loaded up to now for special
     fonts and check them, starting with the lowest font number.  Note
     that this can sometimes lead to surprising results since the
     `fonts' line in the `DESC' file often contains empty positions
     which are filled later on.  For example, consider the following:


          fonts 3 0 0 FOO

     This mounts font `foo' at font position 3.  We assume that `FOO'
     is a special font, containing glyph `foo', and that no font has
     been loaded yet.  The line


          .fspecial BAR BAZ

     makes font `BAZ' special only if font `BAR' is active.  We further
     assume that `BAZ' is really a special font, i.e., the font
     description file contains the `special' keyword, and that it also
     contains glyph `foo' with a special shape fitting to font `BAR'.
     After executing `fspecial', font `BAR' is loaded at font
     position 1, and `BAZ' at position 2.

     We now switch to a new font `XXX', trying to access glyph `foo'
     which is assumed to be missing.  There are neither font-specific
     special fonts for `XXX' nor any other fonts made special with the
     `special' request, so `gtroff' starts the search for special fonts
     in the list of already mounted fonts, with increasing font
     positions.  Consequently, it finds `BAZ' before `FOO' even for
     `XXX' which is not the intended behaviour.

   *Note Font Files::, and *Note Special Fonts::, for more details.

   The list of available symbols is device dependent; see the
`groff_char(7)' man page for a complete list of all glyphs.  For
example, say


     man -Tdvi groff_char > groff_char.dvi

for a list using the default DVI fonts (not all versions of the `man'
program support the `-T' option).  If you want to use an additional
macro package to change the used fonts, `groff' must be called directly:


     groff -Tdvi -mec -man groff_char.7 > groff_char.dvi

   Glyph names not listed in groff_char(7) are derived algorithmically,
using a simplified version of the Adobe Glyph List (AGL) algorithm
which is described in
`http://partners.adobe.com/asn/tech/type/unicodegn.jsp'.  The (frozen)
set of glyph names which can't be derived algorithmically is called
"groff glyph list (GGL)".

   * A glyph for Unicode character U+XXXX[X[X]] which is not a
     composite character will be named `uXXXX[X[X]]'.  X must be an
     uppercase hexadecimal digit.  Examples: `u1234', `u008E',
     `u12DB8'.  The largest Unicode value is 0x10FFFF.  There must be at
     least four `X' digits; if necessary, add leading zeroes (after the
     `u').  No zero padding is allowed for character codes greater than
     0xFFFF.  Surrogates (i.e., Unicode values greater than 0xFFFF
     represented with character codes from the surrogate area
     U+D800-U+DFFF) are not allowed too.

   * A glyph representing more than a single input character will be
     named

          `u' COMPONENT1 `_' COMPONENT2 `_' COMPONENT3 ...

     Example: `u0045_0302_0301'.

     For simplicity, all Unicode characters which are composites must be
     decomposed maximally (this is normalization form D in the Unicode
     standard); for example, `u00CA_0301' is not a valid glyph name
     since U+00CA (LATIN CAPITAL LETTER E WITH CIRCUMFLEX) can be
     further decomposed into U+0045 (LATIN CAPITAL LETTER E) and U+0302
     (COMBINING CIRCUMFLEX ACCENT).  `u0045_0302_0301' is thus the
     glyph name for U+1EBE, LATIN CAPITAL LETTER E WITH CIRCUMFLEX AND
     ACUTE.

   * groff maintains a table to decompose all algorithmically derived
     glyph names which are composites itself.  For example, `u0100'
     (LATIN LETTER A WITH MACRON) will be automatically decomposed into
     `u0041_0304'.  Additionally, a glyph name of the GGL is preferred
     to an algorithmically derived glyph name; groff also automatically
     does the mapping.  Example: The glyph `u0045_0302' will be mapped
     to `^E'.

   * glyph names of the GGL can't be used in composite glyph names; for
     example, `^E_u0301' is invalid.

 - Escape: \(nm
 - Escape: \[name]
 - Escape: \[component1 component2 ...]
     Insert a symbol NAME (two-character name NM) or a composite glyph
     with component glyphs COMPONENT1, COMPONENT2, .... There is no
     special syntax for one-character names - the natural form `\N'
     would collide with escapes.(1) (*note Using Symbols-Footnote-1::)

     If NAME is undefined, a warning of type `char' is generated, and
     the escape is ignored.  *Note Debugging::, for information about
     warnings.

     groff resolves `\[...]' with more than a single component as
     follows:

        * Any component which is found in the GGL will be converted to
          the `uXXXX' form.

        * Any component `uXXXX' which is found in the list of
          decomposable glyphs will be decomposed.

        * The resulting elements are then concatenated with `_'
          inbetween, dropping the leading `u' in all elements but the
          first.

     No check for the existence of any component (similar to `tr'
     request) will be done.

     Examples:

    `\[A ho]'
          `A' maps to `u0041', `ho' maps to `u02DB', thus the final
          glyph name would be `u0041_02DB'.  Note this is not the
          expected result: The ogonek glyph `ho' is a spacing ogonek,
          but for a proper composite a non-spacing ogonek (U+0328) is
          necessary.  Looking into the file `composite.tmac' one can
          find `.composite ho u0328' which changes the mapping of `ho'
          while a composite glyph name is constructed, causing the
          final glyph name to be `u0041_0328'.

    `\[^E u0301]'
    `\[^E aa]'
    `\[E a^ aa]'
    `\[E ^ ']'
          `^E' maps to `u0045_0302', thus the final glyph name is
          `u0045_0302_0301' in all forms (assuming proper calls of the
          `composite' request).

     It is not possible to define glyphs with names like `A ho' within
     a groff font file.  This is not really a limitation; instead, you
     have to define `u0041_0328'.

 - Escape: \C'xxx'
     Typeset the glyph named XXX.(2) (*note Using Symbols-Footnote-2::)
     Normally it is more convenient to use `\[XXX]', but `\C' has the
     advantage that it is compatible with newer versions of AT&T
     `troff' and is available in compatibility mode.

 - Request: .composite from to
     Map glyph name FROM to glyph name TO if it is used in `\[...]'
     with more than one component.  See above for examples.

     This mapping is based on glyph names only; no check for the
     existence of either glyph is done.

     A set of default mappings for many accents can be found in the file
     `composite.tmac' which is loaded at start-up.

 - Escape: \N'n'
     Typeset the glyph with code N in the current font (`n' is *not*
     the input character code).  The number N can be any non-negative
     decimal integer.  Most devices only have glyphs with codes between
     0 and 255; the Unicode output device uses codes in the range
     0-65535.  If the current font does not contain a glyph with that
     code, special fonts are _not_ searched.  The `\N' escape sequence
     can be conveniently used in conjunction with the `char' request:


          .char \[phone] \f[ZD]\N'37'

     The code of each glyph is given in the fourth column in the font
     description file after the `charset' command.  It is possible to
     include unnamed glyphs in the font description file by using a
     name of `---'; the `\N' escape sequence is the only way to use
     these.

     No kerning is applied to glyphs accessed with `\N'.

   Some escape sequences directly map onto special glyphs.

 - Escape: \'
     This is a backslash followed by the apostrophe character, ASCII
     character `0x27' (EBCDIC character `0x7D').  The same as `\[aa]',
     the acute accent.

 - Escape: \`
     This is a backslash followed by ASCII character `0x60' (EBCDIC
     character `0x79' usually).  The same as `\[ga]', the grave accent.

 - Escape: \-
     This is the same as `\[-]', the minus sign in the current font.

 - Request: .cflags n c1 c2 ...
     Input characters and symbols have certain properties associated
     with it.(3) (*note Using Symbols-Footnote-3::)  These properties
     can be modified with the `cflags' request.  The first argument is
     the sum of the desired flags and the remaining arguments are the
     characters or symbols to have those properties.  It is possible to
     omit the spaces between the characters or symbols.

    `1'
          The character ends sentences (initially characters `.?!' have
          this property).

    `2'
          Lines can be broken before the character (initially no
          characters have this property).

    `4'
          Lines can be broken after the character (initially the
          character `-' and the symbols `\[hy]' and `\[em]' have this
          property).

    `8'
          The character overlaps horizontally if used as a horizontal
          line building element.  Initially the symbols `\[ul]',
          `\[rn]', `\[ru]', `\[radicalex]', and `\[sqrtex]' have this
          property.

    `16'
          The character overlaps vertically if used as vertical line
          building element.  Initially symbol `\[br]' has this property.

    `32'
          An end-of-sentence character followed by any number of
          characters with this property is treated as the end of a
          sentence if followed by a newline or two spaces; in other
          words the character is "transparent" for the purposes of
          end-of-sentence recognition - this is the same as having a
          zero space factor in TeX (initially characters `"')]*' and
          the symbols `\[dg]' and `\[rq]' have this property).

 - Request: .char g [string]
 - Request: .fchar g [string]
 - Request: .fschar f g [string]
 - Request: .schar g [string]
     Define a new glyph G to be STRING (which can be empty).(4) (*note
     Using Symbols-Footnote-4::)  Every time glyph G needs to be
     printed, STRING is processed in a temporary environment and the
     result is wrapped up into a single object.  Compatibility mode is
     turned off and the escape character is set to `\' while STRING is
     being processed.  Any emboldening, constant spacing or track
     kerning is applied to this object rather than to individual
     characters in STRING.

     A glyph defined by these requests can be used just like a normal
     glyph provided by the output device.  In particular, other
     characters can be translated to it with the `tr' or `trin'
     requests; it can be made the leader character by the `lc' request;
     repeated patterns can be drawn with the glyph using the `\l' and
     `\L' escape sequences; words containing the glyph can be
     hyphenated correctly if the `hcode' request is used to give the
     glyph's symbol a hyphenation code.

     There is a special anti-recursion feature: Use of `g' within the
     glyph's definition is handled like normal characters and symbols
     not defined with `char'.

     Note that the `tr' and `trin' requests take precedence if `char'
     accesses the same symbol.


          .tr XY
          X
              => Y
          .char X Z
          X
              => Y
          .tr XX
          X
              => Z

     The `fchar' request defines a fallback glyph: `gtroff' only checks
     for glyphs defined with `fchar' if it cannot find the glyph in the
     current font.  `gtroff' carries out this test before checking
     special fonts.

     `fschar' defines a fallback glyph for font F: `gtroff' checks for
     glyphs defined with `fschar' after the list of fonts declared as
     font-specific special fonts with the `fspecial' request, but
     before the list of fonts declared as global special fonts with the
     `special' request.

     Finally, the `schar' request defines a global fallback glyph:
     `gtroff' checks for glyphs defined with `schar' after the list of
     fonts declared as global special fonts with the `special' request,
     but before the already mounted special fonts.

     *Note Using Symbols::, for a detailed description of the glyph
     searching mechanism in `gtroff'.

 - Request: .rchar c1 c2 ...
 - Request: .rfschar f c1 c2 ...
     Remove the definitions of glyphs C1, C2, ....  This undoes the
     effect of a `char', `fchar', or `schar' request.

     It is possible to omit the whitespace between arguments.

     The request `rfschar' removes glyph definitions defined with
     `fschar' for glyph f.

   *Note Special Characters::.


File: groff,  Node: Using Symbols-Footnotes,  Up: Using Symbols

   (1) Note that a one-character symbol is not the same as an input
character, i.e., the character `a' is not the same as `\[a]'.  By
default, `groff' defines only a single one-character symbol, `\[-]'; it
is usually accessed as `\-'.  On the other hand, `gtroff' has the
special feature that `\[charXXX]' is the same as the input character
with character code XXX.  For example, `\[char97]' is identical to the
letter `a' if ASCII encoding is active.

   (2) `\C' is actually a misnomer since it accesses an output glyph.

   (3) Note that the output glyphs themselves don't have such
properties.  For `gtroff', a glyph is a numbered box with a given
width, depth, and height, nothing else.  All manipulations with the
`cflags' request work on the input level.

   (4) `char' is a misnomer since an output glyph is defined.


File: groff,  Node: Special Fonts,  Next: Artificial Fonts,  Prev: Using Symbols,  Up: Fonts and Symbols

Special Fonts
-------------

Special fonts are those that `gtroff' searches when it cannot find the
requested glyph in the current font.  The Symbol font is usually a
special font.

   `gtroff' provides the following two requests to add more special
fonts.  *Note Using Symbols::, for a detailed description of the glyph
searching mechanism in `gtroff'.

   Usually, only non-TTY devices have special fonts.

 - Request: .special [s1 s2 ...]
 - Request: .fspecial f [s1 s2 ...]
     Use the `special' request to define special fonts.  Initially, this
     list is empty.

     Use the `fspecial' request to designate special fonts only when
     font F is active.  Initially, this list is empty.

     Previous calls to `special' or `fspecial' are overwritten; without
     arguments, the particular list of special fonts is set to empty.
     Special fonts are searched in the order they appear as arguments.

     All fonts which appear in a call to `special' or `fspecial' are
     loaded.

     *Note Using Symbols::, for the exact search order of glyphs.


File: groff,  Node: Artificial Fonts,  Next: Ligatures and Kerning,  Prev: Special Fonts,  Up: Fonts and Symbols

Artificial Fonts
----------------

There are a number of requests and escapes for artificially creating
fonts.  These are largely vestiges of the days when output devices did
not have a wide variety of fonts, and when `nroff' and `troff' were
separate programs.  Most of them are no longer necessary in GNU
`troff'.  Nevertheless, they are supported.

 - Escape: \H'height'
 - Escape: \H'+height'
 - Escape: \H'-height'
 - Register: \n[.height]
     Change (increment, decrement) the height of the current font, but
     not the width.  If HEIGHT is zero, restore the original height.
     Default scaling indicator is `z'.

     The read-only number register `.height' contains the font height as
     set by `\H'.

     Currently, only the `-Tps' device supports this feature.

     Note that `\H' doesn't produce an input token in `gtroff'.  As a
     consequence, it can be used in requests like `mc' (which expects a
     single character as an argument) to change the font on the fly:


          .mc \H'+5z'x\H'0'

     In compatibility mode, `gtroff' behaves differently:  If an
     increment or decrement is used, it is always taken relative to the
     current point size and not relative to the previously selected font
     height.  Thus,


          .cp 1
          \H'+5'test \H'+5'test

     prints the word `test' twice with the same font height (five
     points larger than the current font size).

 - Escape: \S'slant'
 - Register: \n[.slant]
     Slant the current font by SLANT degrees.  Positive values slant to
     the right.  Only integer values are possible.

     The read-only number register `.slant' contains the font slant as
     set by `\S'.

     Currently, only the `-Tps' device supports this feature.

     Note that `\S' doesn't produce an input token in `gtroff'.  As a
     consequence, it can be used in requests like `mc' (which expects a
     single character as an argument) to change the font on the fly:


          .mc \S'20'x\S'0'

     This request is incorrectly documented in the original UNIX troff
     manual; the slant is always set to an absolute value.

 - Request: .ul [lines]
     The `ul' request normally underlines subsequent lines if a TTY
     output device is used.  Otherwise, the lines are printed in italics
     (only the term `underlined' is used in the following).  The single
     argument is the number of input lines to be underlined; with no
     argument, the next line is underlined.  If LINES is zero or
     negative, stop the effects of `ul' (if it was active).  Requests
     and empty lines do not count for computing the number of underlined
     input lines, even if they produce some output like `tl'.  Lines
     inserted by macros (e.g. invoked by a trap) do count.

     At the beginning of `ul', the current font is stored and the
     underline font is activated.  Within the span of a `ul' request,
     it is possible to change fonts, but after the last line affected by
     `ul' the saved font is restored.

     This number of lines still to be underlined is associated with the
     current environment (*note Environments::).  The underline font
     can be changed with the `uf' request.

     The `ul' request does not underline spaces.

 - Request: .cu [lines]
     The `cu' request is similar to `ul' but underlines spaces as well
     (if a TTY output device is used).

 - Request: .uf font
     Set the underline font (globally) used by `ul' and `cu'.  By
     default, this is the font at position 2.  FONT can be either a
     non-negative font position or the name of a font.

 - Request: .bd font [offset]
 - Request: .bd font1 font2 [offset]
 - Register: \n[.b]
     Artificially create a bold font by printing each glyph twice,
     slightly offset.

     Two syntax forms are available.

        * Imitate a bold font unconditionally.  The first argument
          specifies the font to embolden, and the second is the number
          of basic units, minus one, by which the two glyphs are
          offset.  If the second argument is missing, emboldening is
          turned off.

          FONT can be either a non-negative font position or the name
          of a font.

          OFFSET is available in the `.b' read-only register if a
          special font is active; in the `bd' request, its default unit
          is `u'.

        * Imitate a bold form conditionally.  Embolden FONT1 by OFFSET
          only if font FONT2 is the current font.  This command can be
          issued repeatedly to set up different emboldening values for
          different current fonts.  If the second argument is missing,
          emboldening is turned off for this particular current font.

          This affects special fonts only (either set up with the
          `special' command in font files or with the `fspecial'
          request).

 - Request: .cs font [width [em-size]]
     Switch to and from "constant glyph space mode".  If activated, the
     width of every glyph is WIDTH/36 ems.  The em size is given
     absolutely by EM-SIZE; if this argument is missing, the em value
     is taken from the current font size (as set with the `ps' request)
     when the font is effectively in use.  Without second and third
     argument, constant glyph space mode is deactivated.

     Default scaling indicator for EM-SIZE is `z'; WIDTH is an integer.


File: groff,  Node: Ligatures and Kerning,  Prev: Artificial Fonts,  Up: Fonts and Symbols

Ligatures and Kerning
---------------------

Ligatures are groups of characters that are run together, i.e, producing
a single glyph.  For example, the letters `f' and `i' can form a
ligature `fi' as in the word `file'.  This produces a cleaner look
(albeit subtle) to the printed output.  Usually, ligatures are not
available in fonts for TTY output devices.

   Most POSTSCRIPT fonts support the fi and fl ligatures.  The C/A/T
typesetter that was the target of AT&T `troff' also supported `ff',
`ffi', and `ffl' ligatures.  Advanced typesetters or `expert' fonts may
include ligatures for `ft' and `ct', although GNU `troff' does not
support these (yet).

   Only the current font is checked for ligatures and kerns; neither
special fonts nor entities defined with the `char' request (and its
siblings) are taken into account.

 - Request: .lg [flag]
 - Register: \n[.lg]
     Switch the ligature mechanism on or off; if the parameter is
     non-zero or missing, ligatures are enabled, otherwise disabled.
     Default is on.  The current ligature mode can be found in the
     read-only number register `.lg' (set to 1 or 2 if ligatures are
     enabled, 0 otherwise).

     Setting the ligature mode to 2 enables the two-character ligatures
     (fi, fl, and ff) and disables the three-character ligatures (ffi
     and ffl).

   "Pairwise kerning" is another subtle typesetting mechanism that
modifies the distance between a glyph pair to improve readability.  In
most cases (but not always) the distance is decreased.  Typewriter-like
fonts and fonts for terminals where all glyphs have the same width
don't use kerning.

 - Request: .kern [flag]
 - Register: \n[.kern]
     Switch kerning on or off.  If the parameter is non-zero or missing,
     enable pairwise kerning, otherwise disable it.  The read-only
     number register `.kern' is set to 1 if pairwise kerning is enabled,
     0 otherwise.

     If the font description file contains pairwise kerning information,
     glyphs from that font are kerned.  Kerning between two glyphs can
     be inhibited by placing `\&' between them: `V\&A'.

     *Note Font File Format::.

   "Track kerning" expands or reduces the space between glyphs.  This
can be handy, for example, if you need to squeeze a long word onto a
single line or spread some text to fill a narrow column.  It must be
used with great care since it is usually considered bad typography if
the reader notices the effect.

 - Request: .tkf f s1 n1 s2 n2
     Enable track kerning for font F.  If the current font is F the
     width of every glyph is increased by an amount between N1 and N2
     (N1, N2 can be negative); if the current point size is less than
     or equal to S1 the width is increased by N1; if it is greater than
     or equal to S2 the width is increased by N2; if the point size is
     greater than or equal to S1 and less than or equal to S2 the
     increase in width is a linear function of the point size.

     The default scaling indicator is `z' for S1 and S2, `p' for N1 and
     N2.

     Note that the track kerning amount is added even to the rightmost
     glyph in a line; for large values it is thus recommended to
     increase the line length by the same amount to compensate it.

   Sometimes, when typesetting letters of different fonts, more or less
space at such boundaries are needed.  There are two escapes to help
with this.

 - Escape: \/
     Increase the width of the preceding glyph so that the spacing
     between that glyph and the following glyph is correct if the
     following glyph is a roman glyph.  For example, if an italic `f'
     is immediately followed by a roman right parenthesis, then in many
     fonts the top right portion of the `f' overlaps the top left of
     the right parenthesis.  Use this escape sequence whenever an
     italic glyph is immediately followed by a roman glyph without any
     intervening space.  This small amount of space is also called
     "italic correction".


 - Escape: \,
     Modify the spacing of the following glyph so that the spacing
     between that glyph and the preceding glyph is correct if the
     preceding glyph is a roman glyph.  Use this escape sequence
     whenever a roman glyph is immediately followed by an italic glyph
     without any intervening space.  In analogy to above, this space
     could be called "left italic correction", but this term isn't used
     widely.


 - Escape: \&
     Insert a zero-width character, which is invisible.  Its intended
     use is to stop interaction of a character with its surrounding.

        * It prevents the insertion of extra space after an
          end-of-sentence character.


               Test.
               Test.
                   => Test.  Test.
               Test.\&
               Test.
                   => Test. Test.

        * It prevents interpretation of a control character at the
          beginning of an input line.


               .Test
                   => warning: `Test' not defined
               \&.Test
                   => .Test

        * It prevents kerning between two glyphs.

        * It is needed to map an arbitrary character to nothing in the
          `tr' request (*note Character Translations::).

 - Escape: \)
     This escape is similar to `\&' except that it behaves like a
     character declared with the `cflags' request to be transparent for
     the purposes of an end-of-sentence character.

     Its main usage is in macro definitions to protect against arguments
     starting with a control character.


          .de xxx
          \)\\$1
          ..
          .de yyy
          \&\\$1
          ..
          This is a test.\c
          .xxx '
          This is a test.
              =>This is a test.'  This is a test.
          This is a test.\c
          .yyy '
          This is a test.
              =>This is a test.' This is a test.



File: groff,  Node: Sizes,  Next: Strings,  Prev: Fonts and Symbols,  Up: gtroff Reference

Sizes
=====

`gtroff' uses two dimensions with each line of text, type size and
vertical spacing.  The "type size" is approximately the height of the
tallest glyph.(1) (*note Sizes-Footnote-1::)  "Vertical spacing" is the
amount of space `gtroff' allows for a line of text; normally, this is
about 20% larger than the current type size.  Ratios smaller than this
can result in hard-to-read text; larger than this, it spreads the text
out more vertically (useful for term papers).  By default, `gtroff'
uses 10 point type on 12 point spacing.

   The difference between type size and vertical spacing is known, by
typesetters, as "leading" (this is pronounced `ledding').

* Menu:

* Changing Type Sizes::
* Fractional Type Sizes::


File: groff,  Node: Sizes-Footnotes,  Up: Sizes

   (1) This is usually the parenthesis.  Note that in most cases the
real dimensions of the glyphs in a font are _not_ related to its type
size!  For example, the standard POSTSCRIPT font families `Times
Roman', `Helvetica', and `Courier' can't be used together at 10pt; to
get acceptable output, the size of `Helvetica' has to be reduced by one
point, and the size of `Courier' must be increased by one point.


File: groff,  Node: Changing Type Sizes,  Next: Fractional Type Sizes,  Prev: Sizes,  Up: Sizes

Changing Type Sizes
-------------------

 - Request: .ps [size]
 - Request: .ps +size
 - Request: .ps -size
 - Escape: \ssize
 - Register: \n[.s]
     Use the `ps' request or the `\s' escape to change (increase,
     decrease) the type size (in points).  Specify SIZE as either an
     absolute point size, or as a relative change from the current size.
     The size 0, or no argument, goes back to the previous size.

     Default scaling indicator of `size' is `z'.  If `size' is zero or
     negative, it is set to 1u.

     The read-only number register `.s' returns the point size in
     points as a decimal fraction.  This is a string.  To get the point
     size in scaled points, use the `.ps' register instead.

     `.s' is associated with the current environment (*note
     Environments::).


          snap, snap,
          .ps +2
          grin, grin,
          .ps +2
          wink, wink, \s+2nudge, nudge,\s+8 say no more!
          .ps 10

     The `\s' escape may be called in a variety of ways.  Much like
     other escapes there must be a way to determine where the argument
     ends and the text begins.  Any of the following forms are valid:

    `\sN'
          Set the point size to N points.  N must be either 0 or in the
          range 4 to 39.

    `\s+N'
    `\s-N'
          Increase or decrease the point size by N points.  N must be
          exactly one digit.

    `\s(NN'
          Set the point size to NN points.  NN must be exactly two
          digits.

    `\s+(NN'
    `\s-(NN'
    `\s(+NN'
    `\s(-NN'
          Increase or decrease the point size by NN points.  NN must be
          exactly two digits.

     Note that `\s' doesn't produce an input token in `gtroff'.  As a
     consequence, it can be used in requests like `mc' (which expects a
     single character as an argument) to change the font on the fly:


          .mc \s[20]x\s[0]

     *Note Fractional Type Sizes::, for yet another syntactical form of
     using the `\s' escape.

 - Request: .sizes s1 s2 ... sn [0]
     Some devices may only have certain permissible sizes, in which case
     `gtroff' rounds to the nearest permissible size.  The `DESC' file
     specifies which sizes are permissible for the device.

     Use the `sizes' request to change the permissible sizes for the
     current output device.  Arguments are in scaled points; the
     `sizescale' line in the `DESC' file for the output device provides
     the scaling factor.  For example, if the scaling factor is 1000,
     then the value 12000 is 12 points.

     Each argument can be a single point size (such as `12000'), or a
     range of sizes (such as `4000-72000').  You can optionally end the
     list with a zero.

 - Request: .vs [space]
 - Request: .vs +space
 - Request: .vs -space
 - Register: \n[.v]
     Change (increase, decrease) the vertical spacing by SPACE.  The
     default scaling indicator is `p'.

     If `vs' is called without an argument, the vertical spacing is
     reset to the previous value before the last call to `vs'.

     `gtroff' creates a warning of type `range' if SPACE is negative;
     the vertical spacing is then set to smallest positive value, the
     vertical resolution (as given in the `.V' register).

     Note that `.vs 0' isn't saved in a diversion since it doesn't
     result in a vertical motion.  You explicitly have to repeat this
     command before inserting the diversion.

     The read-only number register `.v' contains the current vertical
     spacing; it is associated with the current environment (*note
     Environments::).

   The effective vertical line spacing consists of four components.
Breaking a line causes the following actions (in the given order).

   * Move the current point vertically by the "extra pre-vertical line
     space".  This is the minimum value of all `\x' escapes with a
     negative argument in the current output line.

   * Move the current point vertically by the vertical line spacing as
     set with the `vs' request.

   * Output the current line.

   * Move the current point vertically by the "extra post-vertical line
     space".  This is the maximum value of all `\x' escapes with a
     positive argument in the line which has just been output.

   * Move the current point vertically by the "post-vertical line
     spacing" as set with the `pvs' request.

   It is usually better to use `vs' or `pvs' instead of `ls' to produce
double-spaced documents: `vs' and `pvs' have a finer granularity for
the inserted vertical space compared to `ls'; furthermore, certain
preprocessors assume single-spacing.

   *Note Manipulating Spacing::, for more details on the `\x' escape
and the `ls' request.

 - Request: .pvs [space]
 - Request: .pvs +space
 - Request: .pvs -space
 - Register: \n[.pvs]
     Change (increase, decrease) the post-vertical spacing by SPACE.
     The default scaling indicator is `p'.

     If `pvs' is called without an argument, the post-vertical spacing
     is reset to the previous value before the last call to `pvs'.

     `gtroff' creates a warning of type `range' if SPACE is zero or
     negative; the vertical spacing is then set to zero.

     The read-only number register `.pvs' contains the current
     post-vertical spacing; it is associated with the current
     environment (*note Environments::).


File: groff,  Node: Fractional Type Sizes,  Prev: Changing Type Sizes,  Up: Sizes

Fractional Type Sizes
---------------------

A "scaled point" is equal to 1/SIZESCALE points, where SIZESCALE is
specified in the `DESC' file (1 by default).  There is a new scale
indicator `z' which has the effect of multiplying by SIZESCALE.
Requests and escape sequences in `gtroff' interpret arguments that
represent a point size as being in units of scaled points, but they
evaluate each such argument using a default scale indicator of `z'.
Arguments treated in this way are the argument to the `ps' request, the
third argument to the `cs' request, the second and fourth arguments to
the `tkf' request, the argument to the `\H' escape sequence, and those
variants of the `\s' escape sequence that take a numeric expression as
their argument (see below).

   For example, suppose SIZESCALE is 1000; then a scaled point is
equivalent to a millipoint; the request `.ps 10.25' is equivalent to
`.ps 10.25z' and thus sets the point size to 10250 scaled points, which
is equal to 10.25 points.

   `gtroff' disallows the use of the `z' scale indicator in instances
where it would make no sense, such as a numeric expression whose
default scale indicator was neither `u' nor `z'.  Similarly it would
make no sense to use a scaling indicator other than `z' or `u' in a
numeric expression whose default scale indicator was `z', and so
`gtroff' disallows this as well.

   There is also new scale indicator `s' which multiplies by the number
of units in a scaled point.  So, for example, `\n[.ps]s' is equal to
`1m'.  Be sure not to confuse the `s' and `z' scale indicators.

 - Register: \n[.ps]
     A read-only number register returning the point size in scaled
     points.

     `.ps' is associated with the current environment (*note
     Environments::).

 - Register: \n[.psr]
 - Register: \n[.sr]
     The last-requested point size in scaled points is contained in the
     `.psr' read-only number register.  The last requested point size
     in points as a decimal fraction can be found in `.sr'.  This is a
     string-valued read-only number register.

     Note that the requested point sizes are device-independent, whereas
     the values returned by the `.ps' and `.s' registers are not.  For
     example, if a point size of 11pt is requested, and a `sizes'
     request (or a `sizescale' line in a `DESC' file) specifies 10.95pt
     instead, this value is actually used.

     Both registers are associated with the current environment (*note
     Environments::).

   The `\s' escape has the following syntax for working with fractional
type sizes:

`\s[N]'
`\s'N''
     Set the point size to N scaled points; N is a numeric expression
     with a default scale indicator of `z'.

`\s[+N]'
`\s[-N]'
`\s+[N]'
`\s-[N]'
`\s'+N''
`\s'-N''
`\s+'N''
`\s-'N''
     Increase or or decrease the point size by N scaled points; N is a
     numeric expression with a default scale indicator of `z'.

   *Note Font Files::.


File: groff,  Node: Strings,  Next: Conditionals and Loops,  Prev: Sizes,  Up: gtroff Reference

Strings
=======

`gtroff' has string variables, which are entirely for user convenience
(i.e. there are no built-in strings exept `.T', but even this is a
read-write string variable).

 - Request: .ds name [string]
 - Request: .ds1 name [string]
 - Escape: \*n
 - Escape: \*(nm
 - Escape: \*[name arg1 arg2 ...]
     Define and access a string variable NAME (one-character name N,
     two-character name NM).  If NAME already exists, `ds' overwrites
     the previous definition.  Only the syntax form using brackets can
     take arguments which are handled identically to macro arguments;
     the single exception is that a closing bracket as an argument must
     be enclosed in double quotes.  *Note Request and Macro
     Arguments::, and *Note Parameters::.

     Example:


          .ds foo a \\$1 test
          .
          This is \*[foo nice].
              => This is a nice test.

     The `\*' escape "interpolates" (expands in-place) a
     previously-defined string variable.  To be more precise, the stored
     string is pushed onto the input stack which is then parsed by
     `gtroff'.  Similar to number registers, it is possible to nest
     strings, i.e. string variables can be called within string
     variables.

     If the string named by the `\*' escape does not exist, it is
     defined as empty, and a warning of type `mac' is emitted (see
     *Note Debugging::, for more details).

     *Caution:* Unlike other requests, the second argument to the `ds'
     request takes up the entire line including trailing spaces.  This
     means that comments on a line with such a request can introduce
     unwanted space into a string.


          .ds UX \s-1UNIX\s0\u\s-3tm\s0\d \" UNIX trademark

     Instead the comment should be put on another line or have the
     comment escape adjacent with the end of the string.


          .ds UX \s-1UNIX\s0\u\s-3tm\s0\d\"  UNIX trademark

     To produce leading space the string can be started with a double
     quote.  No trailing quote is needed; in fact, any trailing quote is
     included in your string.


          .ds sign "           Yours in a white wine sauce,

     Strings are not limited to a single line of text.  A string can
     span several lines by escaping the newlines with a backslash.  The
     resulting string is stored _without_ the newlines.


          .ds foo lots and lots \
          of text are on these \
          next several lines

     It is not possible to have real newlines in a string.  To put a
     single double quote character into a string, use two consecutive
     double quote characters.

     The `ds1' request turns off compatibility mode while interpreting
     a string.  To be more precise, a "compatibility save" input token
     is inserted at the beginning of  the string, and a "compatibility
     restore" input token at the end.


          .nr xxx 12345
          .ds aa The value of xxx is \\n[xxx].
          .ds1 bb The value of xxx ix \\n[xxx].
          .
          .cp 1
          .
          \*(aa
              => warning: number register `[' not defined
              => The value of xxx is 0xxx].
          \*(bb
              => The value of xxx ix 12345.

     Strings, macros, and diversions (and boxes) share the same name
     space.  Internally, even the same mechanism is used to store them.
     This has some interesting consequences.  For example, it is
     possible to call a macro with string syntax and vice versa.


          .de xxx
          a funny test.
          ..
          This is \*[xxx]
              => This is a funny test.
          
          .ds yyy a funny test
          This is
          .yyy
              => This is a funny test.

     Diversions and boxes can be also called with string syntax.

     Another consequence is that you can copy one-line diversions or
     boxes to a string.


          .di xxx
          a \fItest\fR
          .br
          .di
          .ds yyy This is \*[xxx]\c
          \*[yyy].
              => This is a test.

     As the previous example shows, it is possible to store formatted
     output in strings.  The `\c' escape prevents the insertion of an
     additional blank line in the output.

     Copying diversions longer than a single output line produces
     unexpected results.


          .di xxx
          a funny
          .br
          test
          .br
          .di
          .ds yyy This is \*[xxx]\c
          \*[yyy].
              => test This is a funny.

     Usually, it is not predictable whether a diversion contains one or
     more output lines, so this mechanism should be avoided.  With UNIX
     `troff', this was the only solution to strip off a final newline
     from a diversion.  Another disadvantage is that the spaces in the
     copied string are already formatted, making them unstretchable.
     This can cause ugly results.

     A clean solution to this problem is available in GNU `troff',
     using the requests `chop' to remove the final newline of a
     diversion, and `unformat' to make the horizontal spaces
     stretchable again.


          .box xxx
          a funny
          .br
          test
          .br
          .box
          .chop xxx
          .unformat xxx
          This is \*[xxx].
              => This is a funny test.

     *Note Gtroff Internals::, for more information.

 - Request: .as name [string]
 - Request: .as1 name [string]
     The `as' request is similar to `ds' but appends STRING to the
     string stored as NAME instead of redefining it.  If NAME doesn't
     exist yet, it is created.


          .as sign " with shallots, onions and garlic,

     The `as1' request is similar to `as', but compatibility mode is
     switched off while the appended string is interpreted.  To be more
     precise, a "compatibility save" input token is inserted at the
     beginning of the appended string, and a "compatibility restore"
     input token at the end.

   Rudimentary string manipulation routines are given with the next two
requests.

 - Request: .substring str n1 [n2]
     Replace the string named STR with the substring defined by the
     indices N1 and N2.  The first character in the string has index 0.
     If N2 is omitted, it is taken to be equal to the string's length.
     If the index value N1 or N2 is negative, it is counted from the
     end of the string, going backwards: The last character has
     index -1, the character before the last character has index -2,
     etc.


          .ds xxx abcdefgh
          .substring xxx 1 -4
          \*[xxx]
              => bcde


 - Request: .length reg str
     Compute the number of characters of STR and return it in the
     number register REG.  If REG doesn't exist, it is created.  `str'
     is read in copy mode.


          .ds xxx abcd\h'3i'efgh
          .length yyy \*[xxx]
          \n[yyy]
              => 14


 - Request: .rn xx yy
     Rename the request, macro, diversion, or string XX to YY.

 - Request: .rm xx
     Remove the request, macro, diversion, or string XX.  `gtroff'
     treats subsequent invocations as if the object had never been
     defined.

 - Request: .als new old
     Create an alias named NEW for the request, string, macro, or
     diversion object named OLD.  The new name and the old name are
     exactly equivalent (it is similar to a hard rather than a soft
     link). If OLD is undefined, `gtroff' generates a warning of type
     `mac' and ignores the request.

 - Request: .chop xx
     Remove (chop) the last character from the macro, string, or
     diversion named XX.  This is useful for removing the newline from
     the end of diversions that are to be interpolated as strings.
     This command can be used repeatedly; see *Note Gtroff Internals::,
     for details on nodes inserted additionally by `gtroff'.

   *Note Identifiers::, and *Note Comments::.


File: groff,  Node: Conditionals and Loops,  Next: Writing Macros,  Prev: Strings,  Up: gtroff Reference

Conditionals and Loops
======================

* Menu:

* Operators in Conditionals::
* if-else::
* while::


File: groff,  Node: Operators in Conditionals,  Next: if-else,  Prev: Conditionals and Loops,  Up: Conditionals and Loops

Operators in Conditionals
-------------------------

In `if' and `while' requests, there are several more operators
available:

`e'
`o'
     True if the current page is even or odd numbered (respectively).

`n'
     True if the document is being processed in nroff mode (i.e., the
     `.nroff' command has been issued).

`t'
     True if the document is being processed in troff mode (i.e., the
     `.troff' command has been issued).

`v'
     Always false.  This condition is for compatibility with other
     `troff' versions only (identifying a `-Tversatec' device).

`'XXX'YYY''
     True if the string XXX is equal to the string YYY.  Other
     characters can be used in place of the single quotes; the same set
     of delimiters as for the `\D' escape is used (*note Escapes::).
     `gtroff' formats the strings before being compared:


          .ie "|"\fR|\fP" \
          true
          .el \
          false
              => true

     The resulting motions, glyph sizes, and fonts have to match,(1)
     (*note Operators in Conditionals-Footnote-1::) and not the
     individual motion, size, and font requests.  In the previous
     example, `|' and `\fR|\fP' both result in a roman `|' glyph with
     the same point size and at the same location on the page, so the
     strings are equal.  If `.ft I' had been added before the `.ie',
     the result would be "false" because (the first) `|' produces an
     italic `|' rather than a roman one.

`r XXX'
     True if there is a number register named XXX.

`d XXX'
     True if there is a string, macro, diversion, or request named XXX.

`m XXX'
     True if there is a color named XXX.

`c G'
     True if there is a glyph G available(2) (*note Operators in
     Conditionals-Footnote-2::); G is either an ASCII character or a
     special character (`\(GG' or `\[GGG]'); the condition is also true
     if G has been defined by the `char' request.

   Note that these operators can't be combined with other operators like
`:' or `&'; only a leading `!' (without whitespace between the
exclamation mark and the operator) can be used to negate the result.


     .nr xxx 1
     .ie !r xxx \
     true
     .el \
     false
         => false

   A whitespace after `!' always evaluates to zero (this bizarre
behaviour is due to compatibility with UNIX `troff').


     .nr xxx 1
     .ie ! r xxx \
     true
     .el \
     false
         => r xxx true

   It is possible to omit the whitespace before the argument to the
`r', `d', and `c' operators.

   *Note Expressions::.


File: groff,  Node: Operators in Conditionals-Footnotes,  Up: Operators in Conditionals

   (1) The created output nodes must be identical.  *Note Gtroff
Internals::.

   (2) The name of this conditional operator is a misnomer since it
tests names of output glyphs.


File: groff,  Node: if-else,  Next: while,  Prev: Operators in Conditionals,  Up: Conditionals and Loops

if-else
-------

`gtroff' has if-then-else constructs like other languages, although the
formatting can be painful.

 - Request: .if expr anything
     Evaluate the expression EXPR, and executes ANYTHING (the remainder
     of the line) if EXPR evaluates to a value greater than zero
     (true).  ANYTHING is interpreted as though it was on a line by
     itself (except that leading spaces are swallowed).  *Note
     Expressions::, for more info.


          .nr xxx 1
          .nr yyy 2
          .if ((\n[xxx] == 1) & (\n[yyy] == 2)) true
              => true


 - Request: .nop anything
     Executes ANYTHING.  This is similar to `.if 1'.

 - Request: .ie expr anything
 - Request: .el anything
     Use the `ie' and `el' requests to write an if-then-else.  The
     first request is the `if' part and the latter is the `else' part.


          .ie n .ls 2 \" double-spacing in nroff
          .el   .ls 1 \" single-spacing in troff


 - Escape: \{
 - Escape: \}
     In many cases, an if (or if-else) construct needs to execute more
     than one request.  This can be done using the `\{' and `\}'
     escapes.  The following example shows the possible ways to use
     these escapes (note the position of the opening and closing
     braces).


          .ie t \{\
          .    ds lq ``
          .    ds rq ''
          .\}
          .el \
          .\{\
          .    ds lq "
          .    ds rq "\}


   *Note Expressions::.


File: groff,  Node: while,  Prev: if-else,  Up: Conditionals and Loops

while
-----

`gtroff' provides a looping construct using the `while' request, which
is used much like the `if' (and related) requests.

 - Request: .while expr anything
     Evaluate the expression EXPR, and repeatedly execute ANYTHING (the
     remainder of the line) until EXPR evaluates to 0.


          .nr a 0 1
          .while (\na < 9) \{\
          \n+a,
          .\}
          \n+a
              => 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

     Some remarks.

        * The body of a `while' request is treated like the body of a
          `de' request: `gtroff' temporarily stores it in a macro which
          is deleted after the loop has been exited.  It can
          considerably slow down a macro if the body of the `while'
          request (within the macro) is large.  Each time the macro is
          executed, the `while' body is parsed and stored again as a
          temporary macro.


               .de xxx
               .  nr num 10
               .  while (\\n[num] > 0) \{\
               .    \" many lines of code
               .    nr num -1
               .  \}
               ..

          The traditional and ofter better solution (UNIX `troff'
          doesn't have the `while' request) is to use a recursive macro
          instead which is parsed only once during its definition.


               .de yyy
               .  if (\\n[num] > 0) \{\
               .    \" many lines of code
               .    nr num -1
               .    yyy
               .  \}
               ..
               .
               .de xxx
               .  nr num 10
               .  yyy
               ..

          Note that the number of available recursion levels is set
          to 1000 (this is a compile-time constant value of `gtroff').

        * The closing brace of a `while' body must end a line.


               .if 1 \{\
               .  nr a 0 1
               .  while (\n[a] < 10) \{\
               .    nop \n+[a]
               .\}\}
                   => unbalanced \{ \}


 - Request: .break
     Break out of a `while' loop.  Be sure not to confuse this with the
     `br' request (causing a line break).

 - Request: .continue
     Finish the current iteration of a `while' loop, immediately
     restarting the next iteration.

   *Note Expressions::.


File: groff,  Node: Writing Macros,  Next: Page Motions,  Prev: Conditionals and Loops,  Up: gtroff Reference

Writing Macros
==============

A "macro" is a collection of text and embedded commands which can be
invoked multiple times.  Use macros to define common operations.

 - Request: .de name [end]
 - Request: .de1 name [end]
 - Request: .dei name [end]
 - Request: .dei1 name [end]
     Define a new macro named NAME.  `gtroff' copies subsequent lines
     (starting with the next one) into an internal buffer until it
     encounters the line `..' (two dots).  The optional second argument
     to `de' changes this to a macro to `.END'.

     There can be whitespace after the first dot in the line containing
     the ending token (either `.' or macro `END').

     Here a small example macro called `P' which causes a break and
     inserts some vertical space.  It could be used to separate
     paragraphs.


          .de P
          .  br
          .  sp .8v
          ..

     The following example defines a macro within another.  Remember
     that expansion must be protected twice; once for reading the macro
     and once for executing.


          \# a dummy macro to avoid a warning
          .de end
          ..
          .
          .de foo
          .  de bar end
          .    nop \f[B]Hallo \\\\$1!\f[]
          .  end
          ..
          .
          .foo
          .bar Joe
              => Hallo Joe!

     Since `\f' has no expansion, it isn't necessary to protect its
     backslash.  Had we defined another macro within `bar' which takes
     a parameter, eight backslashes would be necessary before `$1'.

     The `de1' request turns off compatibility mode while executing the
     macro.  On entry, the current compatibility mode is saved and
     restored at exit.


          .nr xxx 12345
          .
          .de aa
          The value of xxx is \\n[xxx].
          ..
          .de1 bb
          The value of xxx ix \\n[xxx].
          ..
          .
          .cp 1
          .
          .aa
              => warning: number register ' not defined
              => The value of xxx is 0xxx].
          .bb
              => The value of xxx ix 12345.

     The `dei' request defines a macro indirectly.  That is, it expands
     strings whose names are NAME or END before performing the append.

     This:


          .ds xx aa
          .ds yy bb
          .dei xx yy

     is equivalent to:


          .de aa bb

     The `dei1' request is similar to `dei' but with compatibility mode
     switched off during execution of the defined macro.

     Using `trace.tmac', you can trace calls to `de' and `de1'.

     Note that macro identifiers are shared with identifiers for
     strings and diversions.

 - Request: .am name [end]
 - Request: .am1 name [end]
 - Request: .ami name [end]
 - Request: .ami1 name [end]
     Works similarly to `de' except it appends onto the macro named
     NAME.  So, to make the previously defined `P' macro actually do
     indented instead of block paragraphs, add the necessary code to the
     existing macro like this:


          .am P
          .ti +5n
          ..

     The `am1' request turns off compatibility mode while executing the
     appended macro piece.  To be more precise, a "compatibility save"
     input token is inserted at the beginning of the appended code, and
     a "compatibility restore" input token at the end.

     The `ami' request appends indirectly, meaning that `gtroff'
     expands strings whose names are NAME or END before performing the
     append.

     The `ami1' request is similar to `ami' but compatibility mode is
     switched off during execution of the defined macro.

     Using `trace.tmac', you can trace calls to `am' and `am1'.

   *Note Strings::, for the `als' request to rename a macro.

   The `de', `am', `di', `da', `ds', and `as' requests (together with
its variants) only create a new object if the name of the macro,
diversion or string diversion is currently undefined or if it is
defined to be a request; normally they modify the value of an existing
object.

 - Request: .return [anything]
     Exit a macro, immediately returning to the caller.

     If called with an argument, exit twice, namely the current macro
     and the macro one level higher.  This is used to define a wrapper
     macro for `return' in `trace.tmac'.

* Menu:

* Copy-in Mode::
* Parameters::


File: groff,  Node: Copy-in Mode,  Next: Parameters,  Prev: Writing Macros,  Up: Writing Macros

Copy-in Mode
------------

When `gtroff' reads in the text for a macro, string, or diversion, it
copies the text (including request lines, but excluding escapes) into
an internal buffer.  Escapes are converted into an internal form,
except for `\n', `\$', `\*', `\\' and `\<RET>' which are evaluated and
inserted into the text where the escape was located.  This is known as
"copy-in" mode or "copy" mode.

   What this means is that you can specify when these escapes are to be
evaluated (either at copy-in time or at the time of use) by insulating
the escapes with an extra backslash.  Compare this to the `\def' and
`\edef' commands in TeX.

   The following example prints the numbers 20 and 10:


     .nr x 20
     .de y
     .nr x 10
     \&\nx
     \&\\nx
     ..
     .y


File: groff,  Node: Parameters,  Prev: Copy-in Mode,  Up: Writing Macros

Parameters
----------

The arguments to a macro or string can be examined using a variety of
escapes.

 - Register: \n[.$]
     The number of arguments passed to a macro or string.  This is a
     read-only number register.

     Note that the `shift' request can change its value.

   Any individual argument can be retrieved with one of the following
escapes:

 - Escape: \$n
 - Escape: \$(nn
 - Escape: \$[nnn]
     Retrieve the Nth, NNth or NNNth argument.  As usual, the first
     form only accepts a single number (larger than zero), the second a
     two-digit number (larger or equal to 10), and the third any
     positive integer value (larger than zero).  Macros and strings can
     have an unlimited number of arguments.  Note that due to copy-in
     mode, use two backslashes on these in actual use to prevent
     interpolation until the macro is actually invoked.

 - Request: .shift [n]
     Shift the arguments 1 position, or as many positions as specified
     by its argument.  After executing this request, argument I becomes
     argument I-N; arguments 1 to N are no longer available.  Shifting
     by negative amounts is currently undefined.

     The register `.$' is adjusted accordingly.

 - Escape: \$*
 - Escape: \$@
     In some cases it is convenient to use all of the arguments at once
     (for example, to pass the arguments along to another macro).  The
     `\$*' escape concatenates all the arguments separated by spaces.  A
     similar escape is `\$@', which concatenates all the arguments with
     each surrounded by double quotes, and separated by spaces.  If not
     in compatibility mode, the input level of double quotes is
     preserved (see *Note Request and Macro Arguments::).

 - Escape: \$0
     The name used to invoke the current macro.  The `als' request can
     make a macro have more than one name.


          .de generic-macro
          .  ...
          .  if \\n[error] \{\
          .    tm \\$0: Houston, we have a problem.
          .    return
          .  \}
          ..
          .
          .als foo generic-macro
          .als bar generic-macro


   *Note Request and Macro Arguments::.


File: groff,  Node: Page Motions,  Next: Drawing Requests,  Prev: Writing Macros,  Up: gtroff Reference

Page Motions
============

*Note Manipulating Spacing::, for a discussion of the main request for
vertical motion, `sp'.

 - Request: .mk [reg]
 - Request: .rt [dist]
     The request `mk' can be used to mark a location on a page, for
     movement to later.  This request takes a register name as an
     argument in which to store the current page location.  With no
     argument it stores the location in an internal register.  The
     results of this can be used later by the `rt' or the `sp' request
     (or the `\v' escape).

     The `rt' request returns _upwards_ to the location marked with the
     last `mk' request.  If used with an argument, return to a position
     which distance from the top of the page is DIST (no previous call
     to `mk' is necessary in this case).  Default scaling indicator is
     `v'.

     Here a primitive solution for a two-column macro.


          .nr column-length 1.5i
          .nr column-gap 4m
          .nr bottom-margin 1m
          .


          .de 2c
          .  br
          .  mk
          .  ll \\n[column-length]u
          .  wh -\\n[bottom-margin]u 2c-trap
          .  nr right-side 0
          ..
          .


          .de 2c-trap
          .  ie \\n[right-side] \{\
          .    nr right-side 0
          .    po -(\\n[column-length]u + \\n[column-gap]u)
          .    \" remove trap
          .    wh -\\n[bottom-margin]u
          .  \}
          .  el \{\
          .    \" switch to right side
          .    nr right-side 1
          .    po +(\\n[column-length]u + \\n[column-gap]u)
          .    rt
          .  \}
          ..
          .


          .pl 1.5i
          .ll 4i
          This is a small test which shows how the
          rt request works in combination with mk.
          
          .2c
          Starting here, text is typeset in two columns.
          Note that this implementation isn't robust
          and thus not suited for a real two-column
          macro.

     Result:


          This is a small test which shows how the
          rt request works in combination with mk.
          
          Starting  here,    isn't    robust
          text is typeset    and   thus  not
          in two columns.    suited  for   a
          Note that  this    real two-column
          implementation     macro.


   The following escapes give fine control of movements about the page.

 - Escape: \v'e'
     Move vertically, usually from the current location on the page (if
     no absolute position operator `|' is used).  The argument E
     specifies the distance to move; positive is downwards and negative
     upwards.  The default scaling indicator for this escape is `v'.
     Beware, however, that `gtroff' continues text processing at the
     point where the motion ends, so you should always balance motions
     to avoid interference with text processing.

     `\v' doesn't trigger a trap.  This can be quite useful; for
     example, consider a page bottom trap macro which prints a marker
     in the margin to indicate continuation of a footnote or something
     similar.

   There are some special-case escapes for vertical motion.

 - Escape: \r
     Move upwards 1v.

 - Escape: \u
     Move upwards .5v.

 - Escape: \d
     Move down .5v.

 - Escape: \h'e'
     Move horizontally, usually from the current location (if no
     absolute position operator `|' is used).  The expression E
     indicates how far to move: positive is rightwards and negative
     leftwards.  The default scaling indicator for this escape is `m'.

     This horizontal space is not discarded at the end of a line.  To
     insert discardable space of a certain length use the `ss' request.

   There are a number of special-case escapes for horizontal motion.

 - Escape: \<SP>
     An unbreakable and unpaddable (i.e. not expanded during filling)
     space.  (Note: This is a backslash followed by a space.)

 - Escape: \~
     An unbreakable space that stretches like a normal inter-word space
     when a line is adjusted.

 - Escape: \|
     A 1/6th em space.  Ignored for TTY output devices (rounded to
     zero).

 - Escape: \^
     A 1/12th em space.  Ignored for TTY output devices (rounded to
     zero).

 - Escape: \0
     A space the size of a digit.

   The following string sets the TeX logo:


     .ds TeX T\h'-.1667m'\v'.224m'E\v'-.224m'\h'-.125m'X

 - Escape: \w'text'
 - Register: \n[st]
 - Register: \n[sb]
 - Register: \n[rst]
 - Register: \n[rsb]
 - Register: \n[ct]
 - Register: \n[ssc]
 - Register: \n[skw]
     Return the width of the specified TEXT in basic units.  This
     allows horizontal movement based on the width of some arbitrary
     text (e.g. given as an argument to a macro).


          The length of the string `abc' is \w'abc'u.
              => The length of the string `abc' is 72u.

     Font changes may occur in TEXT which don't affect current settings.

     After use, `\w' sets several registers:

    `st'
    `sb'
          The highest and lowest point of the baseline, respectively,
          in TEXT.

    `rst'
    `rsb'
          Like the `st' and `sb' registers, but takes account of the
          heights and depths of glyphs.  With other words, this gives
          the highest and lowest point of TEXT.  Values below the
          baseline are negative.

    `ct'
          Defines the kinds of glyphs occurring in TEXT:

         0
               only short glyphs, no descenders or tall glyphs.

         1
               at least one descender.

         2
               at least one tall glyph.

         3
               at least one each of a descender and a tall glyph.

    `ssc'
          The amount of horizontal space (possibly negative) that
          should be added to the last glyph before a subscript.

    `skw'
          How far to right of the center of the last glyph in the `\w'
          argument, the center of an accent from a roman font should be
          placed over that glyph.

 - Escape: \kp
 - Escape: \k(ps
 - Escape: \k[position]
     Store the current horizontal position in the _input_ line in
     number register with name POSITION (one-character name P,
     two-character name PS).  Use this, for example, to return to the
     beginning of a string for highlighting or other decoration.

 - Register: \n[hp]
     The current horizontal position at the input line.

 - Register: \n[.k]
     A read-only number register containing the current horizontal
     output position (relative to the current indentation).

 - Escape: \o'abc'
     Overstrike glyphs A, B, C, ...; the glyphs are centered, and the
     resulting spacing is the largest width of the affected glyphs.

 - Escape: \zg
     Print glyph G with zero width, i.e., without spacing.  Use this to
     overstrike glyphs left-aligned.

 - Escape: \Z'anything'
     Print ANYTHING, then restore the horizontal and vertical position.
     The argument may not contain tabs or leaders.

     The following is an example of a strike-through macro:


          .de ST
          .nr ww \w'\\$1'
          \Z@\v'-.25m'\l'\\n[ww]u'@\\$1
          ..
          .
          This is
          .ST "a test"
          an actual emergency!



File: groff,  Node: Drawing Requests,  Next: Traps,  Prev: Page Motions,  Up: gtroff Reference

Drawing Requests
================

`gtroff' provides a number of ways to draw lines and other figures on
the page.  Used in combination with the page motion commands (see *Note
Page Motions::, for more info), a wide variety of figures can be drawn.
However, for complex drawings these operations can be quite
cumbersome, and it may be wise to use graphic preprocessors like `gpic'
or `ggrn'.  *Note gpic::, and *Note ggrn::, for more information.

   All drawing is done via escapes.

 - Escape: \l'l'
 - Escape: \l'lg'
     Draw a line horizontally.  L is the length of the line to be
     drawn.  If it is positive, start the line at the current location
     and draw to the right; its end point is the new current location.
     Negative values are handled differently: The line starts at the
     current location and draws to the left, but the current location
     doesn't move.

     L can also be specified absolutely (i.e. with a leading `|') which
     draws back to the beginning of the input line.  Default scaling
     indicator is `m'.

     The optional second parameter G is a glyph to draw the line with.
     If this second argument is not specified, `gtroff' uses the
     underscore glyph, `\[ru]'.

     To separate the two arguments (to prevent `gtroff' from
     interpreting a drawing glyph as a scaling indicator if the glyph is
     represented by a single character) use `\&'.

     Here a small useful example:


          .de box
          \[br]\\$*\[br]\l'|0\[rn]'\l'|0\[ul]'
          ..

     Note that this works by outputting a box rule (a vertical line),
     then the text given as an argument and then another box rule.
     Finally, the line drawing escapes both draw from the current
     location to the beginning of the _input_ line - this works because
     the line length is negative, not moving the current point.

 - Escape: \L'l'
 - Escape: \L'lg'
     Draw vertical lines.  Its parameters are similar to the `\l'
     escape, except that the default scaling indicator is `v'.  The
     movement is downwards for positive values, and upwards for
     negative values.  The default glyph is the box rule glyph,
     `\[br]'.  As with the vertical motion escapes, text processing
     blindly continues where the line ends.


          This is a \L'3v'test.

     Here the result, produced with `grotty'.


          This is a
                    |
                    |
                    |test.


 - Escape: \D'command arg ...'
     The `\D' escape provides a variety of drawing functions.  Note
     that on character devices, only vertical and horizontal lines are
     supported within `grotty'; other devices may only support a subset
     of the available drawing functions.

     The default scaling indicator for all subcommands of `\D' is `m'
     for horizontal distances and `v' for vertical ones.  Exceptions
     are `\D'f ...'' and `\D't ...'' which use `u' as the default, and
     `\D'FX ...'' which arguments are treated similar to the `defcolor'
     request.

    `\D'l DX DY''
          Draw a line from the current location to the relative point
          specified by (DX,DY), where positive values mean down and
          right, respectively.  The end point of the line is the new
          current location.

          The following example is a macro for creating a box around a
          text string; for simplicity, the box margin is taken as a
          fixed value, 0.2m.


               .de BOX
               .  nr @wd \w'\\$1'
               \h'.2m'\
               \h'-.2m'\v'(.2m - \\n[rsb]u)'\
               \D'l 0 -(\\n[rst]u - \\n[rsb]u + .4m)'\
               \D'l (\\n[@wd]u + .4m) 0'\
               \D'l 0 (\\n[rst]u - \\n[rsb]u + .4m)'\
               \D'l -(\\n[@wd]u + .4m) 0'\
               \h'.2m'\v'-(.2m - \\n[rsb]u)'\
               \\$1\
               \h'.2m'
               ..

          First, the width of the string is stored in register `@wd'.
          Then, four lines are drawn to form a box, properly offset by
          the box margin.  The registers `rst' and `rsb' are set by the
          `\w' escape, containing the largest height and depth of the
          whole string.

    `\D'c D''
          Draw a circle with a diameter of D with the leftmost point at
          the current position.  After drawing, the current location is
          positioned at the rightmost point of the circle.

    `\D'C D''
          Draw a solid circle with the same parameters and behaviour as
          an outlined circle.  No outline is drawn.

    `\D'e X Y''
          Draw an ellipse with a horizontal diameter of X and a vertical
          diameter of Y with the leftmost point at the current position.
          After drawing, the current location is positioned at the
          rightmost point of the ellipse.

    `\D'E X Y''
          Draw a solid ellipse with the same parameters and behaviour
          as an outlined ellipse.  No outline is drawn.

    `\D'a DX1 DY1 DX2 DY2''
          Draw an arc clockwise from the current location through the
          two specified relative locations (DX1,DY1) and (DX2,DY2).
          The coordinates of the first point are relative to the
          current position, and the coordinates of the second point are
          relative to the first point.  After drawing, the current
          position is moved to the final point of the arc.

    `\D'~ DX1 DY1 DX2 DY2 ...''
          Draw a spline from the current location to the relative point
          (DX1,DY1) and then to (DX2,DY2), and so on.  The current
          position is moved to the terminal point of the drawn curve.

    `\D'f N''
          Set the shade of gray to be used for filling solid objects
          to N; N must be an integer between 0 and 1000, where 0
          corresponds solid white and 1000 to solid black, and values
          in between correspond to intermediate shades of gray.  This
          applies only to solid circles, solid ellipses, and solid
          polygons.  By default, a level of 1000 is used.

          Despite of being silly, the current point is moved
          horizontally to the right by N.

          Don't use this command!  It has the serious drawback that it
          will be always rounded to the next integer multiple of the
          horizontal resolution (the value of the `hor' keyword in the
          `DESC' file).  Use `\M' (*note Colors::) or `\D'Fg ...''
          instead.

    `\D'p DX1 DY1 DX2 DY2 ...''
          Draw a polygon from the current location to the relative
          position (DX1,DY1) and then to (DX2,DY2) and so on.  When the
          specified data points are exhausted, a line is drawn back to
          the starting point.  The current position is changed by
          adding the sum of all arguments with odd index to the actual
          horizontal position and the even ones to the vertical
          position.

    `\D'P DX1 DY1 DX2 DY2 ...''
          Draw a solid polygon with the same parameters and behaviour
          as an outlined polygon.  No outline is drawn.

          Here a better variant of the box macro to fill the box with
          some color.  Note that the box must be drawn before the text
          since colors in `gtroff' are not transparent; the filled
          polygon would hide the text completely.


               .de BOX
               .  nr @wd \w'\\$1'
               \h'.2m'\
               \h'-.2m'\v'(.2m - \\n[rsb]u)'\
               \M[lightcyan]\
               \D'P 0 -(\\n[rst]u - \\n[rsb]u + .4m) \
                    (\\n[@wd]u + .4m) 0 \
                    0 (\\n[rst]u - \\n[rsb]u + .4m) \
                    -(\\n[@wd]u + .4m) 0'\
               \h'.2m'\v'-(.2m - \\n[rsb]u)'\
               \M[]\
               \\$1\
               \h'.2m'
               ..

    `\D't N''
          Set the current line thickness to N machine units.  A value of
          zero selects the smallest available line thickness.  A
          negative value makes the line thickness proportional to the
          current point size (this is the default behaviour of AT&T
          `troff').

          Despite of being silly, the current point is moved
          horizontally to the right by N.

    `\D'FSCHEME COLOR_COMPONENTS''
          Change current fill color.  SCHEME is a single letter
          denoting the color scheme: `r' (rgb), `c' (cmy), `k' (cmyk),
          `g' (gray), or `d' (default color).  The color components use
          exactly the same syntax as in the `defcolor' request (*note
          Colors::); the command `\D'Fd'' doesn't take an argument.

          _No_ position changing!

          Examples:


          \D'Fg .3'      \" same gray as \D'f 700' \D'Fr #0000ff' \"
          blue

   *Note Graphics Commands::.

 - Escape: \b'string'
     "Pile" a sequence of glyphs vertically, and center it vertically
     on the current line.  Use it to build large brackets and braces.

     Here an example how to create a large opening brace:


          \b'\[lt]\[bv]\[lk]\[bv]\[lb]'

     The first glyph is on the top, the last glyph in STRING is at the
     bottom.  Note that `gtroff' separates the glyphs vertically by 1m,
     and the whole object is centered 0.5m above the current baseline;
     the largest glyph width is used as the width for the whole object.
     This rather unflexible positioning algorithm doesn't work with
     `-Tdvi' since the bracket pieces vary in height for this device.
     Instead, use the `eqn' preprocessor.

     *Note Manipulating Spacing::, how to adjust the vertical spacing
     with the `\x' escape.


File: groff,  Node: Traps,  Next: Diversions,  Prev: Drawing Requests,  Up: gtroff Reference

Traps
=====

"Traps" are locations, which, when reached, call a specified macro.
These traps can occur at a given location on the page, at a given
location in the current diversion, at a blank line, after a certain
number of input lines, or at the end of input.

   Setting a trap is also called "planting".  It is also said that a
trap is "sprung" if the associated macro is executed.

* Menu:

* Page Location Traps::
* Diversion Traps::
* Input Line Traps::
* Blank Line Traps::
* End-of-input Traps::


File: groff,  Node: Page Location Traps,  Next: Diversion Traps,  Prev: Traps,  Up: Traps

Page Location Traps
-------------------

"Page location traps" perform an action when `gtroff' reaches or passes
a certain vertical location on the page.  Page location traps have a
variety of purposes, including:

   * setting headers and footers

   * setting body text in multiple columns

   * setting footnotes

 - Request: .vpt flag
 - Register: \n[.vpt]
     Enable vertical position traps if FLAG is non-zero, or disables
     them otherwise.  Vertical position traps are traps set by the `wh'
     or `dt' requests.  Traps set by the `it' request are not vertical
     position traps.  The parameter that controls whether vertical
     position traps are enabled is global.  Initially vertical position
     traps are enabled.  The current setting of this is available in the
     `.vpt' read-only number register.

     Note that a page can't be ejected if `vpt' is set to zero.

 - Request: .wh dist [macro]
     Set a page location trap.  Non-negative values for DIST set the
     trap relative to the top of the page; negative values set the trap
     relative to the bottom of the page.  Default scaling indicator is
     `v'.

     MACRO is the name of the macro to execute when the trap is sprung.
     If MACRO is missing, remove the first trap (if any) at DIST.

     The following is a simple example of how many macro packages set
     headers and footers.


          .de hd                \" Page header
          '  sp .5i
          .  tl 'Title''date'
          '  sp .3i
          ..
          .
          .de fo                \" Page footer
          '  sp 1v
          .  tl ''%''
          '  bp
          ..
          .
          .wh 0   hd            \" trap at top of the page
          .wh -1i fo            \" trap one inch from bottom

     A trap at or below the bottom of the page is ignored; it can be
     made active by either moving it up or increasing the page length
     so that the trap is on the page.

     It is possible to have more than one trap at the same location; to
     do so, the traps must be defined at different locations, then
     moved together with the `ch' request; otherwise the second trap
     would replace the first one.  Earlier defined traps hide later
     defined traps if moved to the same position (the many empty lines
     caused by the `bp' request are omitted in the following example):


          .de a
          .  nop a
          ..
          .de b
          .  nop b
          ..
          .de c
          .  nop c
          ..
          .
          .wh 1i a
          .wh 2i b
          .wh 3i c
          .bp
              => a b c


          .ch b 1i
          .ch c 1i
          .bp
              => a


          .ch a 0.5i
          .bp
              => a b


 - Register: \n[.t]
     A read-only number register holding the distance to the next trap.

     If there are no traps between the current position and the bottom
     of the page, it contains the distance to the page bottom.  In a
     diversion, the distance to the page bottom is infinite (the
     returned value is the biggest integer which can be represented in
     `groff') if there are no diversion traps.

 - Request: .ch macro [dist]
     Change the location of a trap.  The first argument is the name of
     the macro to be invoked at the trap, and the second argument is
     the new location for the trap (note that the parameters are
     specified in opposite order as in the `wh' request).  This is
     useful for building up footnotes in a diversion to allow more
     space at the bottom of the page for them.

     Default scaling indicator for DIST is `v'.  If DIST is missing,
     the trap is removed.


 - Register: \n[.ne]
     The read-only number register `.ne' contains the amount of space
     that was needed in the last `ne' request that caused a trap to be
     sprung.  Useful in conjunction with the `.trunc' register.  *Note
     Page Control::, for more information.

     Since the `.ne' register is only set by traps it doesn't make much
     sense to use it outside of trap macros.

 - Register: \n[.trunc]
     A read-only register containing the amount of vertical space
     truncated by the most recently sprung vertical position trap, or,
     if the trap was sprung by an `ne' request, minus the amount of
     vertical motion produced by the `ne' request.  In other words, at
     the point a trap is sprung, it represents the difference of what
     the vertical position would have been but for the trap, and what
     the vertical position actually is.

     Since the `.trunc' register is only set by traps it doesn't make
     much sense to use it outside of trap macros.

 - Register: \n[.pe]
     A read-only register which is set to 1 while a page is ejected with
     the `bp' request (or by the end of input).

     Outside of traps this register is always zero.  In the following
     example, only the second call to `x' is caused by `bp'.


          .de x
          \&.pe=\\n[.pe]
          .br
          ..
          .wh 1v x
          .wh 4v x
          A line.
          .br
          Another line.
          .br
              => A line.
                 .pe=0
                 Another line.
          
                 .pe=1


   An important fact to consider while designing macros is that
diversions and traps do not interact normally.  For example, if a trap
invokes a header macro (while outputting a diversion) which tries to
change the font on the current page, the effect will not be visible
before the diversion has completely been printed (except for input
protected with `\!' or `\?') since the data in the diversion is already
formatted.  In most cases, this is not the expected behaviour.


File: groff,  Node: Diversion Traps,  Next: Input Line Traps,  Prev: Page Location Traps,  Up: Traps

Diversion Traps
---------------

 - Request: .dt [dist macro]
     Set a trap _within_ a diversion.  DIST is the location of the trap
     (identical to the `wh' request; default scaling indicator is `v')
     and MACRO is the name of the macro to be invoked.  If called
     without arguments, the diversion trap is removed.

     Note that there exists only a single diversion trap.

     The number register `.t' still works within diversions.  *Note
     Diversions::, for more information.


File: groff,  Node: Input Line Traps,  Next: Blank Line Traps,  Prev: Diversion Traps,  Up: Traps

Input Line Traps
----------------

 - Request: .it n macro
 - Request: .itc n macro
     Set an input line trap.  N is the number of lines of input which
     may be read before springing the trap, MACRO is the macro to be
     invoked.  Request lines are not counted as input lines.

     For example, one possible use is to have a macro which prints the
     next N lines in a bold font.


          .de B
          .  it \\$1 B-end
          .  ft B
          ..
          .
          .de B-end
          .  ft R
          ..

     The `itc' request is identical except that an interrupted text
     line (ending with `\c') is not counted as a separate line.

     Both requests are associated with the current environment (*note
     Environments::); switching to another environment disables the
     current input trap, and going back reactivates it, restoring the
     number of already processed lines.


File: groff,  Node: Blank Line Traps,  Next: End-of-input Traps,  Prev: Input Line Traps,  Up: Traps

Blank Line Traps
----------------

 - Request: .blm macro
     Set a blank line trap.  `gtroff' executes MACRO when it encounters
     a blank line in the input file.


File: groff,  Node: End-of-input Traps,  Prev: Blank Line Traps,  Up: Traps

End-of-input Traps
------------------

 - Request: .em macro
     Set a trap at the end of input.  MACRO is executed after the last
     line of the input file has been processed.

     For example, if the document had to have a section at the bottom
     of the last page for someone to approve it, the `em' request could
     be used.


          .de approval
          .  ne 5v
          .  sp |(\\n[.t] - 6v)
          .  in +4i
          .  lc _
          .  br
          Approved:\t\a
          .  sp
          Date:\t\t\a
          ..
          .
          .em approval


