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# ethers

    ETHERS(3)               System Library Functions Manual              ETHERS(3)

    NAME
         ether_aton, ether_ntoa, ether_addr, ether_ntohost, ether_hostton,
         ether_line - get ethers entry

    SYNOPSIS
         #include <netinet/if_ether.h>

         char *
         ether_ntoa(struct ether_addr *e);

         struct ether_addr *
         ether_aton(char *s);

         int
         ether_ntohost(char *hostname, struct ether_addr *e);

         int
         ether_hostton(char *hostname, struct ether_addr *e);

         int
         ether_line(char *l, struct ether_addr *e, char *hostname);

    DESCRIPTION
         Ethernet addresses are represented by the following structure:

               struct ether_addr {
                       u_int8_t  ether_addr_octet[6];
               };

         The ether_ntoa() function converts this structure into an ASCII string of
         the form ``xx:xx:xx:xx:xx:xx'', consisting of 6 hexadecimal numbers sepa-
         rated by colons.  It returns a pointer to a static buffer that is reused
         for each call.  The ether_aton() converts an ASCII string of the same
         form and to a structure containing the 6 octets of the address.  It
         returns a pointer to a static structure that is reused for each call.

         The ether_ntohost() and ether_hostton() functions interrogate the
         database mapping host names to Ethernet addresses, /etc/ethers.  The
         ether_ntohost() function looks up the given Ethernet address and writes
         the associated host name into the character buffer passed.  This buffer
         should be MAXHOSTNAMELEN characters in size.  The ether_hostton() func-
         tion looks up the given host name and writes the associated Ethernet
         address into the structure passed.  Both functions return zero if they
         find the requested host name or address, and -1 if not.

         Each call reads /etc/ethers from the beginning; if a `+' appears alone on
         a line in the file, then ether_hostton() will consult the ethers.byname
         YP map, and ether_ntohost() will consult the ethers.byaddr YP map.

         The ether_line() function parses a line from the /etc/ethers file and
         fills in the passed struct ether_addr and character buffer with the Eth-
         ernet address and host name on the line.  It returns zero if the line was
         successfully parsed and -1 if not.  The character buffer should be
         MAXHOSTNAMELEN characters in size.

    FILES
         /etc/ethers

    SEE ALSO
         ethers(5)

    HISTORY
         The ether_ntoa(), ether_aton(), ether_ntohost(), ether_hostton(), and
         ether_line() functions were adopted from SunOS and appeared in NetBSD 0.9
         b.

    BUGS
         The data space used by these functions is static; if future use requires
         the data, it should be copied before any subsequent calls to these func-
         tions overwrite it.

    BSD                            December 16, 1993                           BSD

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