PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (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
       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
           one to four hexadecimal digits 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 POSIX.1‐2017, <arpa_inet.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                     INET_NTOP(3POSIX)