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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.
       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 VALUE
       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
       set to EAFNOSUPPORT.
CONFORMING TO
       POSIX.1-2001.
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 ALSO
       getaddrinfo(3), inet(3), inet_ntop(3)
COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux                             2008-06-18                      INET_PTON(3)