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ETHERS(3)              FreeBSD Library Functions Manual              ETHERS(3)

NAME
     ethers, ether_line, ether_aton, ether_ntoa, ether_ntohost, ether_hostton
     - Ethernet address conversion and lookup routines

LIBRARY
     Standard C Library (libc, -lc)

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

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

     struct ether_addr *
     ether_aton(const char *a);

     char *
     ether_ntoa(const struct ether_addr *n);

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

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

DESCRIPTION
     These functions operate on ethernet addresses using an ether_addr
     structure, which is defined in the header file <netinet/if_ether.h>:

           /*
            * The number of bytes in an ethernet (MAC) address.
            */
           #define ETHER_ADDR_LEN          6

           /*
            * Structure of a 48-bit Ethernet address.
            */
           struct  ether_addr {
                   u_char octet[ETHER_ADDR_LEN];
           };

     The function ether_line() scans l, an ASCII string in ethers(5) format
     and sets e to the ethernet address specified in the string and h to the
     hostname.  This function is used to parse lines from /etc/ethers into
     their component parts.

     The ether_aton() function converts an ASCII representation of an ethernet
     address into an ether_addr structure.  Likewise, ether_ntoa() converts an
     ethernet address specified as an ether_addr structure into an ASCII
     string.

     The ether_ntohost() and ether_hostton() functions map ethernet addresses
     to their corresponding hostnames as specified in the /etc/ethers
     database.  The ether_ntohost() function converts from ethernet address to
     hostname, and ether_hostton() converts from hostname to ethernet address.

RETURN VALUES
     The ether_line() function returns zero on success and non-zero if it was
     unable to parse any part of the supplied line l.  It returns the
     extracted ethernet address in the supplied ether_addr structure e and the
     hostname in the supplied string h.

     On success, ether_ntoa() returns a pointer to a string containing an
     ASCII representation of an ethernet address.  If it is unable to convert
     the supplied ether_addr structure, it returns a NULL pointer.  Likewise,
     ether_aton() returns a pointer to an ether_addr structure on success and
     a NULL pointer on failure.

     The ether_ntohost() and ether_hostton() functions both return zero on
     success or non-zero if they were unable to find a match in the
     /etc/ethers database.

NOTES
     The user must insure that the hostname strings passed to the
     ether_line(), ether_ntohost() and ether_hostton() functions are large
     enough to contain the returned hostnames.

NIS INTERACTION
     If the /etc/ethers contains a line with a single + in it, the
     ether_ntohost() and ether_hostton() functions will attempt to consult the
     NIS ethers.byname and ethers.byaddr maps in addition to the data in the
     /etc/ethers file.

SEE ALSO
     ethers(5), yp(8)

HISTORY
     This particular implementation of the ethers library functions were
     written for and first appeared in FreeBSD 2.1.

BUGS
     The ether_aton() and ether_ntoa() functions returns values that are
     stored in static memory areas which may be overwritten the next time they
     are called.

FreeBSD 11.0-PRERELEASE         April 12, 1995         FreeBSD 11.0-PRERELEASE

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | NOTES | NIS INTERACTION | SEE ALSO | HISTORY | BUGS

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