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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | EXAMPLE | SEE ALSO | COLOPHON |
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. dst is written in network byte order.
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 zeros, 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.
For an explanation of the terms used in this section, see
attributes(7).
┌────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├────────────┼───────────────┼────────────────┤
│inet_pton() │ Thread safety │ MT-Safe locale │
└────────────┴───────────────┴────────────────┘
POSIX.1-2001, POSIX.1-2008.
Unlike inet_aton(3) and inet_addr(3), inet_pton() supports IPv6
addresses. On the other hand, inet_pton() accepts only 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
Program source
#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 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2016-07-17 INET_PTON(3)
Pages that refer to this page: getent(1), getaddrinfo(3), gethostbyname(3), getipnodebyname(3), inet(3), inet_ntop(3), systemd.network(5)