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Name

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

Synopsis

cc [ flag ... ] file ... -lsocket -lnsl [ library ... ] 


#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>

char *ether_ntoa (struct ether_addr *e);

struct ether_addr *ether_aton (char *s);

int ether_ntohost (char *hostname, struct ether_addr *e);

int ether_hostton (char *hostname, struct ether_addr *e);

int ether_line (char *l, struct ether_addr *e, char *hostname);

MT-Level

MT-Safe

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 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, the NIS maps ‘‘ethers.byname’’ and ‘‘ethers.byaddr’’ and the NIS + table ‘‘ethers’’. The sources and their lookup order are specified in the /etc/nsswitch.conf file (see nsswitch.conf(4) 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(4) .

Files

/etc/ethers
/etc/nsswitch.conf

See Also

ethers(4) , nsswitch.conf(4)

Bugs

Programs that call ether_hostton() or ether_ntohost() routines cannot be linked statically since the implementation of these routines requires dynamic linker functionality to access shared objects at run time.

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