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.
       dst is written in network byte order.

       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.

ATTRIBUTES
       For  an	explanation  of	 the  terms  used   in	 this	section,   see
       attributes(7).

       +------------+---------------+----------------+
       |Interface   | Attribute	    | Value	     |
       +------------+---------------+----------------+
       |inet_pton() | Thread safety | MT-Safe locale |
       +------------+---------------+----------------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

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 4.10 of the Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2016-07-17			  INET_PTON(3)