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 dec-
	      imal 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 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 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 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
", 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
", str);

	   exit(EXIT_SUCCESS);
       }

SEE ALSO

       getaddrinfo(3), inet(3), inet_ntop(3)

COLOPHON

       This page is part of release 3.44 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)