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



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

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 ''xx''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 (""00::00::00::00::00::00::00::00"") 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 ''xx''s are the hexadecimal values of the six high-order
           16-bit pieces of the address, and the ''dd''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(3)
