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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 <&lt;arpa/inet.h>&gt;

       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 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 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.

BUGS
       AF_INET6  does  not  recognize IPv4 addresses.  An explicit IPv4-mapped
       IPv6 address must be supplied in src instead.

NOTES
       Unlike  inet_aton(3)  and  inet_addr(3),  inet_pton()   supports   IPv6
       addresses.   On the other hand, inet_pton() only accepts 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).

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

       #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 3.05 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)