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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 struc-
     ture, 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 data-
     base.  ether_ntohost() converts from ethernet address to hostname,	and
     ether_hostton() converts from hostname to ethernet	address.

RETURN VALUES
     ether_line() 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)

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.

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

FreeBSD	9.3			April 12, 1995			   FreeBSD 9.3

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

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