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# link_addr

    LINK_ADDR(3)            System Library Functions Manual           LINK_ADDR(3)

    NAME
         link_addr, link_ntoa - elementary address specification routines for link
         level access

    SYNOPSIS
         #include <sys/types.h>
         #include <sys/socket.h>
         #include <net/if_dl.h>

         void
         link_addr(const char *addr, struct sockaddr_dl *sdl);

         char *
         link_ntoa(const struct sockaddr_dl *sdl);

    DESCRIPTION
         The link_addr() function interprets character strings representing link-
         level addresses, returning binary information suitable for use in system
         calls.  link_ntoa() takes a link-level address and returns an ASCII
         string representing some of the information present, including the link
         level address itself, and the interface name or number, if present.  This
         facility is experimental and is still subject to change.

         For link_addr(), the string addr may contain an optional network inter-
         face identifier of the form ``name unit-number'', suitable for the first
         argument to ifconfig(8), followed in all cases by a colon and an inter-
         face address in the form of groups of hexadecimal digits separated by
         periods.  Each group represents a byte of address; address bytes are
         filled left to right from low order bytes through high order bytes.

         Thus le0:8.0.9.13.d.30 represents an Ethernet address to be transmitted
         on the first Lance Ethernet interface.

    RETURN VALUES
         link_ntoa() always returns a null-terminated string.  link_addr() has no
         return value.  (See BUGS.)

    SEE ALSO
         iso(4), ifconfig(8)

    HISTORY
         The link_addr() and link_ntoa() functions appeared in 4.3BSD-Reno.

    BUGS
         The returned values for link_ntoa reside in a static memory area.

         The function link_addr() should diagnose improperly formed input, and
         there should be an unambiguous way to recognize this.

         If the sdl_len field of the link socket address sdl is 0, link_ntoa()
         will not insert a colon before the interface address bytes.  If this
         translated address is given to link_addr() without inserting an initial
         colon, the latter will not interpret it correctly.

    BSD                              July 28, 1993                             BSD

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