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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

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.

RETURN VALUE

CONFORMING TO

NOTES

BUGS

EXAMPLE

$ ./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

COLOPHON

Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

CONFORMING TO

NOTES

BUGS

EXAMPLE

Program source

SEE ALSO

COLOPHON

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