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 .