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man pages section 3: Basic Library Functions

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Updated: Friday, August 13, 2021
 
 

ether_hostton(3C)

Name

ethers, ether_ntoa, ether_aton, ether_ntohost, ether_hostton, ether_line - Ethernet address mapping operations

Synopsis

#include <sys/types.h>
#include <sys/ethernet.h>

char *ether_ntoa(const struct ether_addr *e);
struct ether_addr *ether_aton(const char *s);
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 addresses to their ASCII representations or their corresponding host names, and vice versa.

The function ether_ntoa() converts a 48 bit Ethernet address 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 each 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 address; the function returns NULL if the string cannot be scanned successfully.

The function ether_ntohost() maps an Ethernet address (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 address; the function modifies the Ethernet address 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 nsswitch.conf(5) configuration.

The function ether_line() scans a line, pointed to by l, and sets the hostname and the Ethernet address, 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).

Usage

Few systems other than boot servers have other machines listed in their ethers file, making it unlikely that host names will be able to be retrieved for a given Ethernet address. Most systems instead rely on arp(4P) to map between Ethernet addresses and IP addresses on their local network.

Files

/etc/ethers

Ethernet address to hostname database

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
MT-Safe

See Also

arp(4P), ethers(5), nsswitch.conf(5), attributes(7)

History

These functions have been present since the initial release of Solaris.