ETHERS(3)               NetBSD Library Functions Manual              ETHERS(3)

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

LIBRARY
     Standard C Library (libc, -lc)

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

     char *
     ether_ntoa(const struct ether_addr *e);

     struct ether_addr *
     ether_aton(const char *s);

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

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

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

DESCRIPTION
     Ethernet addresses are represented by the following structure:

           struct ether_addr {
                   u_char  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 data
     base 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.  The
     ether_hostton() function 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
     Ethernet address and host name on the line.  It returns zero if the line
     was successfully parsed and -1 if not.

     The hostname buffer for ether_line() and ether_ntohost() should be at
     least MAXHOSTNAMELEN + 1 characters long, to prevent a buffer overflow
     during parsing.

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 1.0.

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.

NetBSD 7.0                     November 2, 1997                     NetBSD 7.0

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