inet_pton man page on ElementaryOS

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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.

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() 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 3.54 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)
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