#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.

       The following address families are currently supported:

              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.

              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

              See RFC 2373 for further details on the representation  of  IPv6

       inet_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
       addresses,  and IPv4 addresses in numbers-and-dots notation, see getad-

       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
           $ ./a.out i6 0:0:0:0:0:FFFF:

   Program source

       #include <arpa/inet.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>

       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]);

           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");

           if (inet_ntop(domain, buf, str, INET6_ADDRSTRLEN) == NULL) {

Linux                             2008-06-18                      INET_PTON(3)
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