ETHERS(3)						   BSD 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() con-
     verts 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.	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 ether-
     net 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

     yp(8), ethers(5)

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 written for and first appeared in FreeBSD 2.1.

BSD
								  April 12, 1995							       BSD