INET_PTON(3) Linux Programmer's Manual INET_PTON(3)NAMEinet_pton - convert IPv4 and IPv6 addresses from text to binary form
SYNOPSIS
#include <arpa/inet.h>
int inet_pton(int af, const char *src, void *dst);
DESCRIPTION
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 nota‐
tion 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.
RETURN VALUEinet_pton() returns 1 on success (network address was successfully con‐
verted). 0 is returned if src does not contain a character string rep‐
resenting 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.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
┌────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├────────────┼───────────────┼────────────────┤
│inet_pton() │ Thread safety │ MT-Safe locale │
└────────────┴───────────────┴────────────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
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 num‐
ber 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 getad‐
drinfo(3).
BUGS
AF_INET6 does not recognize IPv4 addresses. An explicit IPv4-mapped
IPv6 address must be supplied in src instead.
EXAMPLE
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);
}
SEE ALSOgetaddrinfo(3), inet(3), inet_ntop(3)COLOPHON
This page is part of release 4.14 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 2017-09-15 INET_PTON(3)
