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INET_PTON(3) Linux Programmer's Manual INET_PTON(3)
inet_pton - convert IPv4 and IPv6 addresses from text to binary form
#include <arpa/inet.h>
int inet_pton(int af, const char *src, void *dst);
This function converts the character string src into a network address
structure in the af address family, then copies the network address structure
to dst. The af argument must be either AF_INET or AF_INET6.
The following address families are currently supported:
AF_INET
src points to a character string containing an IPv4 network address in
dotted-decimal format, "ddd.ddd.ddd.ddd", where ddd is a decimal number
of up to three digits in the range 0 to 255. The address is converted
to a struct in_addr and copied to dst, which must be sizeof(struct
in_addr) (4) bytes (32 bits) long.
AF_INET6
src points to a character string containing an IPv6 network address.
The address is converted to a struct in6_addr and copied to dst, which
must be sizeof(struct in6_addr) (16) bytes (128 bits) long. The
allowed formats for IPv6 addresses follow these rules:
1. The preferred format is x:x:x:x:x:x:x:x. This form consists of
eight hexadecimal numbers, each of which expresses a 16-bit value
(i.e., each x can be up to 4 hex digits).
2. A series of contiguous zero values in the preferred format can be
abbreviated to ::. Only one instance of :: can occur in an address.
For example, the loopback address 0:0:0:0:0:0:0:1 can be abbreviated
as ::1. The wildcard address, consisting of all zeroes, can be
written as ::.
3. An alternate format is useful for expressing IPv4-mapped IPv6
addresses. This form is written as x:x:x:x:x:x:d.d.d.d, where the
six leading xs are hexadecimal values that define the six most-
significant 16-bit pieces of the address (i.e., 96 bits), and the ds
express a value in dotted-decimal notation that defines the least
significant 32 bits of the address. An example of such an address
is ::FFFF:204.152.189.116.
See RFC 2373 for further details on the representation of IPv6
addresses.
inet_pton() returns 1 on success (network address was successfully converted).
0 is returned if src does not contain a character string representing a valid
network address in the specified address family. If af does not contain a
valid address family, -1 is returned and errno is set to EAFNOSUPPORT.
POSIX.1-2001.
Unlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6 addresses. On
the other hand, inet_pton() only accepts IPv4 addresses in dotted-decimal
notation, whereas inet_aton(3) and inet_addr(3) allow the more general
numbers-and-dots notation (hexadecimal and octal number formats, and formats
that don't require all four bytes to be explicitly written). For an interface
that handles both IPv6 addresses, and IPv4 addresses in numbers-and-dots
notation, see getaddrinfo(3).
AF_INET6 does not recognize IPv4 addresses. An explicit IPv4-mapped IPv6
address must be supplied in src instead.
The program below demonstrates the use of inet_pton() and inet_ntop(3). Here
are some example runs:
$ ./a.out i6 0:0:0:0:0:0:0:0
::
$ ./a.out i6 1:0:0:0:0:0:0:8
1::8
$ ./a.out i6 0:0:0:0:0:FFFF:204.152.189.116
::ffff:204.152.189.116
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{
unsigned char buf[sizeof(struct in6_addr)];
int domain, s;
char str[INET6_ADDRSTRLEN];
if (argc != 3) {
fprintf(stderr, "Usage: %s {i4|i6|<num>} string\n", argv[0]);
exit(EXIT_FAILURE);
}
domain = (strcmp(argv[1], "i4") == 0) ? AF_INET :
(strcmp(argv[1], "i6") == 0) ? AF_INET6 : atoi(argv[1]);
s = inet_pton(domain, argv[2], buf);
if (s <= 0) {
if (s == 0)
fprintf(stderr, "Not in presentation format");
else
perror("inet_pton");
exit(EXIT_FAILURE);
}
if (inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL) {
perror("inet_ntop");
exit(EXIT_FAILURE);
}
printf("%s\n", str);
exit(EXIT_SUCCESS);
}
getaddrinfo(3), inet(3), inet_ntop(3)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-06-18 INET_PTON(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface