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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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INET_NTOP(3P) POSIX Programmer's Manual INET_NTOP(3P)
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.
inet_ntop, inet_pton — convert IPv4 and IPv6 addresses between
binary and text form
#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);
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 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.
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.
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.
None.
None.
None.
None.
The Base Definitions volume of POSIX.1‐2017, arpa_inet.h(0p)
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(3P)
Pages that refer to this page: arpa_inet.h(0p), freeaddrinfo(3p), getnameinfo(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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