NAME

       inet_ntop, inet_pton - convert IPv4 and IPv6 addresses between binary and text form

SYNOPSIS

       #include <arpa/inet.h>

       const char *inet_ntop(int af, const void *restrict src,
              char *restrict dst, socklen_t size);
       int inet_pton(int af, const char *restrict src, void *restrict dst);

DESCRIPTION

       The  inet_ntop()  function shall convert a numeric address into a text string suitable for
       presentation. The af argument shall specify the family of the address. This can be AF_INET
        or  AF_INET6.   The  src  argument  points  to a buffer holding an IPv4 address if the af
       argument is AF_INET,  or an IPv6 address if the af argument is AF_INET6;  the address must
       be  in  network  byte order. The dst argument points to a buffer where the function stores
       the resulting text string; it shall not be NULL. The size argument specifies the  size  of
       this  buffer,  which  shall  be  large  enough  to  hold  the text string (INET_ADDRSTRLEN
       characters for IPv4,    INET6_ADDRSTRLEN characters for IPv6).

       The inet_pton() function shall convert an address in its standard text  presentation  form
       into  its  numeric  binary form.  The af argument shall specify the family of the address.
       The AF_INET    and AF_INET6 address families shall be supported. The src  argument  points
       to the string being passed in. The dst argument points to a buffer into which the function
       stores the numeric address; this shall be large enough to hold  the  numeric  address  (32
       bits for AF_INET,  128 bits for AF_INET6).

       If the af argument of inet_pton() is AF_INET, the src string shall be in the standard IPv4
       dotted-decimal form:

              ddd.ddd.ddd.ddd

       where "ddd" is a one to three digit decimal number between 0 and 255 (see  inet_addr()  ).
       The  inet_pton()  function  does  not  accept  other  formats  (such as the octal numbers,
       hexadecimal numbers, and fewer than four numbers that inet_addr() accepts).

       If the af argument of inet_pton() is AF_INET6, the src string  shall  be  in  one  of  the
       following standard IPv6 text forms:

        1. The  preferred  form is "x:x:x:x:x:x:x:x" , where the 'x' s are the hexadecimal values
           of the eight 16-bit pieces of the address. Leading zeros in individual fields  can  be
           omitted, but there shall be at least one numeral in every field.

        2. A  string  of  contiguous zero fields in the preferred form can be shown as "::" . The
           "::" can only appear once in an address. Unspecified addresses (  "0:0:0:0:0:0:0:0"  )
           may be represented simply as "::" .

        3. A  third  form that is sometimes more convenient when dealing with a mixed environment
           of IPv4 and IPv6 nodes is "x:x:x:x:x:x:d.d.d.d" , where the 'x' s are the  hexadecimal
           values  of  the  six  high-order  16-bit  pieces of the address, and the 'd' s are the
           decimal values of the four low-order  8-bit  pieces  of  the  address  (standard  IPv4
           representation).

       Note:  A  more extensive description of the standard representations of IPv6 addresses can
              be found in RFC 2373.

RETURN VALUE

       The inet_ntop() function shall return a pointer to the buffer containing the  text  string
       if the conversion succeeds, and NULL otherwise, and set errno to indicate the error.

       The  inet_pton()  function  shall  return  1  if the conversion succeeds, with the address
       pointed to by dst in network byte order. It shall return 0 if the input  is  not  a  valid
       IPv4  dotted-decimal  string     or  a valid IPv6 address string,  or -1 with errno set to
       [EAFNOSUPPORT] if the af argument is unknown.

ERRORS

       The inet_ntop() and inet_pton() functions shall fail if:

       EAFNOSUPPORT

              The af argument is invalid.

       ENOSPC The size of the inet_ntop() result buffer is inadequate.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       The Base Definitions volume of IEEE Std 1003.1-2001, <arpa/inet.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2003  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .