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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.

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 4.04 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
       http://www.kernel.org/doc/man-pages/.



Linux				  2015-08-08			  INET_PTON(3)