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 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
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 writ-
ten for and first appeared in FreeBSD 2.1.
BSD April 12, 1995 BSD
Mac OS X 10.8 - Generated Mon Aug 27 16:32:24 CDT 2012