Linux
2019-03-06
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Manual pages about using GNU/Linux for development
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Linux kernel and C library user-space interface documentation
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 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:
|
|||||||
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 |
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 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).
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];
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);
}
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]);
(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 (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);
}
perror("inet_ntop");
exit(EXIT_FAILURE);
}
printf("%s\n", str);
exit(EXIT_SUCCESS); }