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INET_NTOP(3P)              POSIX Programmer's Manual             INET_NTOP(3P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

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  fami-
       lies  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()  func-
       tion 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  (stan-
           dard 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 suc-
       ceeds, 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 net-
       work 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                        INET_NTOP(3P)