ether_aton(3) Library Functions Manual ether_aton(3)
NAME
ether_aton, ether_ntoa, ether_ntohost, ether_hostton, ether_line,
ether_ntoa_r, ether_aton_r - Ethernet address manipulation routines
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <netinet/ether.h>
char *ether_ntoa(const struct ether_addr *addr);
struct ether_addr *ether_aton(const char *asc);
int ether_ntohost(char *hostname, const struct ether_addr *addr);
int ether_hostton(const char *hostname, struct ether_addr *addr);
int ether_line(const char *line, struct ether_addr *addr,
char *hostname);
/* GNU extensions */
char *ether_ntoa_r(const struct ether_addr *addr, char *buf);
struct ether_addr *ether_aton_r(const char *asc,
struct ether_addr *addr);
DESCRIPTION
ether_aton() converts the 48-bit Ethernet host address asc from the
standard hex-digits-and-colons notation into binary data in network
byte order and returns a pointer to it in a statically allocated
buffer, which subsequent calls will overwrite. ether_aton() returns
NULL if the address is invalid.
The ether_ntoa() function converts the Ethernet host address addr given
in network byte order to a string in standard hex-digits-and-colons no-
tation, omitting leading zeros. The string is returned in a statically
allocated buffer, which subsequent calls will overwrite.
The ether_ntohost() function maps an Ethernet address to the corre-
sponding hostname in /etc/ethers and returns nonzero if it cannot be
found.
The ether_hostton() function maps a hostname to the corresponding Eth-
ernet address in /etc/ethers and returns nonzero if it cannot be found.
The ether_line() function parses a line in /etc/ethers format (ethernet
address followed by whitespace followed by hostname; '#' introduces a
comment) and returns an address and hostname pair, or nonzero if it
cannot be parsed. The buffer pointed to by hostname must be suffi-
ciently long, for example, have the same length as line.
The functions ether_ntoa_r() and ether_aton_r() are reentrant thread-
safe versions of ether_ntoa() and ether_aton() respectively, and do not
use static buffers.
The structure ether_addr is defined in <net/ethernet.h> as:
struct ether_addr {
uint8_t ether_addr_octet[6];
}
ATTRIBUTES
For an explanation of the terms used in this section, see attrib-
utes(7).
┌─────────────────────────────────────────┬───────────────┬───────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────────┼───────────────┼───────────┤
│ ether_aton(), ether_ntoa() │ Thread safety │ MT-Unsafe │
├─────────────────────────────────────────┼───────────────┼───────────┤
│ ether_ntohost(), ether_hostton(), │ Thread safety │ MT-Safe │
│ ether_line(), ether_ntoa_r(), │ │ │
│ ether_aton_r() │ │ │
└─────────────────────────────────────────┴───────────────┴───────────┘
STANDARDS
None.
HISTORY
4.3BSD, SunOS.
BUGS
In glibc 2.2.5 and earlier, the implementation of ether_line() is bro-
ken.
SEE ALSO
ethers(5)
Linux man-pages 6.7 2023-10-31 ether_aton(3)
Generated by dwww version 1.16 on Mon Jul 13 11:01:20 CEST 2026.