'\" et

.TH INET_NTOP "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

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.

.SH NAME

inet_ntop,

inet_pton

\(em convert IPv4 and IPv6 addresses between binary and text form

.SH SYNOPSIS

.LP

.nf

#include <arpa/inet.h>

.P

const char *inet_ntop(int \fIaf\fP, const void *restrict \fIsrc\fP,

    char *restrict \fIdst\fP, socklen_t \fIsize\fP);

int inet_pton(int \fIaf\fP, const char *restrict \fIsrc\fP, void *restrict \fIdst\fP);

.fi

.SH DESCRIPTION

The

\fIinet_ntop\fR()

function shall convert a numeric address into a text string suitable

for presentation. The

.IR af

argument shall specify the family of the address. This can be AF_INET

or AF_INET6.

The

.IR src

argument points to a buffer holding an IPv4 address if the

.IR af

argument is AF_INET,

or an IPv6 address if the

.IR af

argument is AF_INET6;

the address must be in network byte order. The

.IR dst

argument points to a buffer where the function stores the resulting

text string; it shall not be NULL. The

.IR 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).

.P

The

\fIinet_pton\fR()

function shall convert an address in its standard text presentation

form into its numeric binary form. The

.IR af

argument shall specify the family of the address. The AF_INET

and AF_INET6

address families shall be supported. The

.IR src

argument points to the string being passed in. The

.IR 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).

.P

If the

.IR af

argument of

\fIinet_pton\fR()

is AF_INET, the

.IR src

string shall be in the standard IPv4 dotted-decimal form:

.sp

.RS 4

.nf

\fB

ddd.ddd.ddd.ddd

.fi \fR

.P

.RE

.P

where

.BR \(dqddd\(dq 

is a one to three digit decimal number between 0 and 255 (see

.IR "\fIinet_addr\fR\^(\|)").

The

\fIinet_pton\fR()

function does not accept other formats (such as the octal numbers,

hexadecimal numbers, and fewer than four numbers that

\fIinet_addr\fR()

accepts).

.P

If the

.IR af

argument of

\fIinet_pton\fR()

is AF_INET6, the

.IR src

string shall be in one of the following standard IPv6 text forms:

.IP " 1." 4

The preferred form is

.BR \(dqx:x:x:x:x:x:x:x\(dq ,

where the

.BR '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.

.IP " 2." 4

A string of contiguous zero fields in the preferred form can be shown

as

.BR \(dq::\(dq .

The

.BR \(dq::\(dq 

can only appear once in an address. Unspecified addresses (\c

.BR \(dq0:0:0:0:0:0:0:0\(dq )

may be represented simply as

.BR \(dq::\(dq .

.IP " 3." 4

A third form that is sometimes more convenient when dealing with a

mixed environment of IPv4 and IPv6 nodes is

.BR \(dqx:x:x:x:x:x:d.d.d.d\(dq ,

where the

.BR 'x' s

are the hexadecimal values of the six high-order 16-bit pieces of the

address, and the

.BR 'd' s

are the decimal values of the four low-order 8-bit pieces of the

address (standard IPv4 representation).

.TP 10

.BR Note:

A more extensive description of the standard representations of IPv6

addresses can be found in RFC\ 2373.

.P

.SH "RETURN VALUE"

The

\fIinet_ntop\fR()

function shall return a pointer to the buffer containing the text

string if the conversion succeeds, and NULL otherwise, and set

.IR errno

to indicate the error.

.P

The

\fIinet_pton\fR()

function shall return 1 if the conversion succeeds, with the address

pointed to by

.IR 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 \(mi1 with

.IR errno

set to

.BR [EAFNOSUPPORT] 

if the

.IR af

argument is unknown.

.SH ERRORS

The

\fIinet_ntop\fR()

and

\fIinet_pton\fR()

functions shall fail if:

.TP

.BR EAFNOSUPPORT

.br

The

.IR af

argument is invalid.

.TP

.BR ENOSPC

The size of the

\fIinet_ntop\fR()

result buffer is inadequate.

.LP

.IR "The following sections are informative."

.SH "EXAMPLES"

None.

.SH "APPLICATION USAGE"

None.

.SH "RATIONALE"

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<arpa_inet.h>\fP"

.SH COPYRIGHT

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 .