mirror of https://github.com/mkerrisk/man-pages
163 lines
5.0 KiB
Groff
163 lines
5.0 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" libc.info (from glibc distribution)
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.\" Modified Sat Jul 24 19:12:00 1993 by Rik Faith <faith@cs.unc.edu>
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.\" Modified Sun Sep 3 20:29:36 1995 by Jim Van Zandt <jrv@vanzandt.mv.com>
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.\" Changed network into host byte order (for inet_network),
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.\" Andreas Jaeger <aj@arthur.rhein-neckar.de>, 980130.
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.\"
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.TH INET 3 2001-07-25 "GNU" "Linux Programmer's Manual"
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.SH NAME
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inet_aton, inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof,
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inet_netof \- Internet address manipulation routines
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.SH SYNOPSIS
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.nf
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.B #include <sys/socket.h>
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.B #include <netinet/in.h>
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.B #include <arpa/inet.h>
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.sp
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.BI "int inet_aton(const char *" cp ", struct in_addr *" inp );
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.sp
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.BI "in_addr_t inet_addr(const char *" cp );
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.sp
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.BI "in_addr_t inet_network(const char *" cp );
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.sp
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.BI "char *inet_ntoa(struct in_addr " in );
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.sp
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.BI "struct in_addr inet_makeaddr(int " net ", int " host );
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.sp
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.BI "in_addr_t inet_lnaof(struct in_addr " in );
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.sp
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.BI "in_addr_t inet_netof(struct in_addr " in );
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.fi
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.SH DESCRIPTION
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.BR inet_aton ()
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converts the Internet host address \fIcp\fP from the
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standard numbers-and-dots notation into binary data and stores it in
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the structure that \fIinp\fP points to.
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.BR inet_aton ()
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returns
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non-zero if the address is valid, zero if not.
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.PP
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The
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.BR inet_addr ()
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function converts the Internet host address
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\fIcp\fP from numbers-and-dots notation into binary data in network
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byte order.
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If the input is invalid, INADDR_NONE (usually \-1) is returned.
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This is an \fIobsolete\fP interface to
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.BR inet_aton (),
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described
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immediately above; it is obsolete because \-1 is a valid address
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(255.255.255.255), and
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.BR inet_aton ()
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provides a cleaner way
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to indicate error return.
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.PP
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The
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.BR inet_network ()
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function extracts
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a number in host byte order suitable for use as an Internet address
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from \fIcp\fP, which is a string in numbers-and-dots notation.
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If the input is invalid, \-1 is returned.
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.PP
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The
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.BR inet_ntoa ()
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function converts the Internet host address
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\fIin\fP given in network byte order to a string in standard
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numbers-and-dots notation.
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The string is returned in a statically
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allocated buffer, which subsequent calls will overwrite.
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.PP
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The
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.BR inet_makeaddr ()
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function makes an Internet host address
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in network byte order by combining the network number \fInet\fP
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with the local address \fIhost\fP in network \fInet\fP, both in
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local host byte order.
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.PP
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The
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.BR inet_lnaof ()
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function returns the local host address part
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of the Internet address \fIin\fP.
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The local host address is returned
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in local host byte order.
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.PP
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The
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.BR inet_netof ()
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function returns the network number part of
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the Internet Address \fIin\fP.
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The network number is returned in
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local host byte order.
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.PP
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The structure \fIin_addr\fP as used in
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.BR inet_ntoa (),
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.BR inet_makeaddr (),
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.BR inet_lnoaf ()
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and
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.BR inet_netof ()
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is defined in \fInetinet/in.h\fP as:
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.sp
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.RS
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.nf
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struct in_addr {
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unsigned long int s_addr;
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}
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.fi
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.RE
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.PP
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Note that on the i80x86 the host byte order is Least Significant Byte
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first (little endian), whereas the network byte order, as used on the
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Internet, is Most Significant Byte first (big endian).
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.SH "CONFORMING TO"
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4.3BSD.
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.BR inet_addr (),
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.BR inet_aton (),
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and
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.BR inet_ntoa ()
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are specified in POSIX.1-2001.
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.SH NOTES
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When you using numbers-and-dots notation for addresses,
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be aware that each number will be interpreted as octal
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if preceded by a 0 and as hexadecimal if preceded by 0x.
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For example, \fBinet_aton("226.000.000.037", &t)\fP will
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interpret the address as \fI226.0.0.31\fP and not \fI226.0.0.37\fP.
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.SS Glibc Notes
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In order to expose the declaration of
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.BR inet_aton (),
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one of the feature test macros _BSD_SOURCE, _SVID_SOURCE, or
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_GNU_SOURCE must be defined.
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.SH "SEE ALSO"
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.BR gethostbyname (3),
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.BR getnetent (3),
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.BR inet_ntop (3),
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.BR inet_pton (3),
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.BR hosts (5),
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.BR networks (5)
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