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)