PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

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

SYNOPSIS         top

       #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         top

       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(3p)).  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         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       The Base Definitions volume of POSIX.1‐2008, arpa_inet.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                       INET_NTOP(3P)