ETHERS(3SOCKET) Sockets Library Functions ETHERS(3SOCKET)
NAME
ethers, ether_ntoa, ether_ntoa_r, ether_aton, ether_aton_r,
ether_ntohost, ether_hostton, ether_line - Ethernet address mapping
operations
SYNOPSIS
cc [
flag ... ]
file ...
-lsocket -lnsl [
library ... ]
#include <sys/types.h>
#include <sys/ethernet.h>
char *ether_ntoa(
const struct ether_addr *e);
char *ether_ntoa_r(
const struct ether_addr *e,
char *s);
struct ether_addr *ether_aton(
const char *s);
struct ether_addr *ether_aton_r(
const char *s,
struct ether_addr *e);
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 *l,
struct ether_addr *e,
char *hostname);
DESCRIPTION
These routines are useful for mapping 48 bit Ethernet numbers to
their ASCII representations or their corresponding host names, and
vice versa.
The function
ether_ntoa() converts a 48 bit Ethernet number pointed
to by
e to its standard
ASCII representation; it returns a pointer to
the
ASCII string. The representation is of the form
x:
x:
x:
x:
x:
x where
x is a hexadecimal number between
0 and
ff. The function
ether_aton() converts an
ASCII string in the standard representation
back to a 48 bit Ethernet number; the function returns
NULL if the
string cannot be scanned successfully.
The functions
ether_ntoa() and
ether_aton() return values in per-
thread buffers, one for each function. A second call to one of these
functions will overwrite the previous value. The functions
ether_ntoa_r() and
ether_aton_r() behave identically to their non-
reentrant versions; however, instead of using a per-thread buffer,
they use caller supplied buffers. It is the callers responsibility to
ensure that the character buffer passed to
ether_ntoa_r() is at least
ETHERADDRSTRL bytes large -- the minimum size to hold the ASCII
representation of a 48 bit Ethernet number and a null terminator.
The function
ether_ntohost() maps an Ethernet number (pointed to by
e) to its associated hostname. The string pointed to by hostname
must be long enough to hold the hostname and a
NULL character. The
function returns zero upon success and non-zero upon failure.
Inversely, the function
ether_hostton() maps a hostname string to its
corresponding Ethernet number; the function modifies the Ethernet
number pointed to by
e. The function also returns zero upon success
and non-zero upon failure. In order to do the mapping, both these
functions may lookup one or more of the following sources: the ethers
file and the
NIS maps
ethers.byname and
ethers.byaddr. The sources
and their lookup order are specified in the
/etc/nsswitch.conf file.
See
nsswitch.conf(5) for details.
The function
ether_line() scans a line, pointed to by
l, and sets the
hostname and the Ethernet number, pointed to by
e. The string pointed
to by hostname must be long enough to hold the hostname and a
NULL character. The function returns zero upon success and non-zero upon
failure. The format of the scanned line is described by
ethers(5).
FILES
/etc/ethers Ethernet address to hostname database or domain
/etc/nsswitch.conf configuration file for the name service switch
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT-Level | MT-Safe |
+---------------+-----------------+
SEE ALSO
ethers(5),
nsswitch.conf(5),
attributes(7) February 17, 2023 ETHERS(3SOCKET)
