INET_PTON(3)		   Linux Programmers Manual		 INET_PTON(3)



NAME
       inet_pton - convert IPv4 and IPv6 addresses from text to binary form

SYNOPSIS
       #include 

       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  dont	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 
       #include 
       #include 
       #include 

       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|} 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)