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 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
       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.

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()  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 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];

           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 3.25 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)