INET_NTOP(P) POSIX Programmer's Manual 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 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 buf-
fer 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 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. Unspeci-
fied 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 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 Technol-
ogy -- 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 original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .
IEEE
/The Open Group 2003 INET_NTOP(P)