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man page for inet_pton

INET_PTON(3)						     Linux Programmer's Manual						      INET_PTON(3)

NAME
inet_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 dec- imal 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. RETURN VALUE
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. 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 getaddrinfo(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 ALSO
getaddrinfo(3), inet(3), inet_ntop(3) Linux 2019-03-06 INET_PTON(3)

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