INET_NTOP(P) INET_NTOP(P)
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 argu-
ment 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, hex-
adecimal 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 fol-
lowing 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 deci-
mal values of the four low-order 8-bit pieces of the address (standard IPv4 represen-
tation).
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 IEEE Std 1003.1-2001, <arpa/inet.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
POSIX 2003 INET_NTOP(P)
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