arm-2011.03/share/doc/arm-arm-none-linux-gnueabi/html/libc/Interface-Naming.html - nest-cam/v366/arm-none-linux-gnueabi-i686-pc-linux-gnu - Git at Google

 <html lang="en">
 <head>
 <title>Interface Naming - The GNU C Library</title>
 <meta http-equiv="Content-Type" content="text/html">
 <meta name="description" content="The GNU C Library">
 <meta name="generator" content="makeinfo 4.13">
 <link title="Top" rel="start" href="index.html#Top">
 <link rel="up" href="Sockets.html#Sockets" title="Sockets">
 <link rel="prev" href="Socket-Addresses.html#Socket-Addresses" title="Socket Addresses">
 <link rel="next" href="Local-Namespace.html#Local-Namespace" title="Local Namespace">
 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
 <!--
 This file documents the GNU C library.

 This is Edition 0.12, last updated 2007-10-27,
 of `The GNU C Library Reference Manual', for version
 2.8 (Sourcery G++ Lite 2011.03-41).

 Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002,
 2003, 2007, 2008, 2010 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
 any later version published by the Free Software Foundation; with the
 Invariant Sections being ``Free Software Needs Free Documentation''
 and ``GNU Lesser General Public License'', the Front-Cover texts being
 ``A GNU Manual'', and with the Back-Cover Texts as in (a) below.  A
 copy of the license is included in the section entitled "GNU Free
 Documentation License".

 (a) The FSF's Back-Cover Text is: ``You have the freedom to
 copy and modify this GNU manual.  Buying copies from the FSF
 supports it in developing GNU and promoting software freedom.''-->
 <meta http-equiv="Content-Style-Type" content="text/css">
 <style type="text/css"><!--
   pre.display { font-family:inherit }
   pre.format  { font-family:inherit }
   pre.smalldisplay { font-family:inherit; font-size:smaller }
   pre.smallformat  { font-family:inherit; font-size:smaller }
   pre.smallexample { font-size:smaller }
   pre.smalllisp    { font-size:smaller }
   span.sc    { font-variant:small-caps }
   span.roman { font-family:serif; font-weight:normal; }
   span.sansserif { font-family:sans-serif; font-weight:normal; }
 --></style>
 <link rel="stylesheet" type="text/css" href="../cs.css">
 </head>
 <body>
 <div class="node">
 <a name="Interface-Naming"></a>
 <p>
 Next:&nbsp;<a rel="next" accesskey="n" href="Local-Namespace.html#Local-Namespace">Local Namespace</a>,
 Previous:&nbsp;<a rel="previous" accesskey="p" href="Socket-Addresses.html#Socket-Addresses">Socket Addresses</a>,
 Up:&nbsp;<a rel="up" accesskey="u" href="Sockets.html#Sockets">Sockets</a>
 <hr>
 </div>

 <h3 class="section">16.4 Interface Naming</h3>

 <p>Each network interface has a name.  This usually consists of a few
 letters that relate to the type of interface, which may be followed by a
 number if there is more than one interface of that type.  Examples
 might be <code>lo</code> (the loopback interface) and <code>eth0</code> (the first
 Ethernet interface).

    <p>Although such names are convenient for humans, it would be clumsy to
 have to use them whenever a program needs to refer to an interface.  In
 such situations an interface is referred to by its <dfn>index</dfn>, which is
 an arbitrarily-assigned small positive integer.

    <p>The following functions, constants and data types are declared in the
 header file <samp><span class="file">net/if.h</span></samp>.

 <!-- net/if.h -->
 <div class="defun">
 &mdash; Constant: size_t <b>IFNAMSIZ</b><var><a name="index-IFNAMSIZ-1666"></a></var><br>
 <blockquote><p>This constant defines the maximum buffer size needed to hold an
 interface name, including its terminating zero byte.
 </p></blockquote></div>

 <!-- net/if.h -->
 <!-- IPv6 basic API -->
 <div class="defun">
 &mdash; Function: unsigned int <b>if_nametoindex</b> (<var>const char *ifname</var>)<var><a name="index-if_005fnametoindex-1667"></a></var><br>
 <blockquote><p>This function yields the interface index corresponding to a particular
 name.  If no interface exists with the name given, it returns 0.
 </p></blockquote></div>

 <!-- net/if.h -->
 <!-- IPv6 basic API -->
 <div class="defun">
 &mdash; Function: char * <b>if_indextoname</b> (<var>unsigned int ifindex, char *ifname</var>)<var><a name="index-if_005findextoname-1668"></a></var><br>
 <blockquote><p>This function maps an interface index to its corresponding name.  The
 returned name is placed in the buffer pointed to by <code>ifname</code>, which
 must be at least <code>IFNAMSIZ</code> bytes in length.  If the index was
 invalid, the function's return value is a null pointer, otherwise it is
 <code>ifname</code>.
 </p></blockquote></div>

 <!-- net/if.h -->
 <!-- IPv6 basic API -->
 <div class="defun">
 &mdash; Data Type: <b>struct if_nameindex</b><var><a name="index-struct-if_005fnameindex-1669"></a></var><br>
 <blockquote><p>This data type is used to hold the information about a single
 interface.  It has the following members:

           <dl>
 <dt><code>unsigned int if_index;</code><dd>This is the interface index.

           <br><dt><code>char *if_name</code><dd>This is the null-terminated index name.

         </dl>
         </p></blockquote></div>

 <!-- net/if.h -->
 <!-- IPv6 basic API -->
 <div class="defun">
 &mdash; Function: struct if_nameindex * <b>if_nameindex</b> (<var>void</var>)<var><a name="index-if_005fnameindex-1670"></a></var><br>
 <blockquote><p>This function returns an array of <code>if_nameindex</code> structures, one
 for every interface that is present.  The end of the list is indicated
 by a structure with an interface of 0 and a null name pointer.  If an
 error occurs, this function returns a null pointer.

         <p>The returned structure must be freed with <code>if_freenameindex</code> after
 use.
 </p></blockquote></div>

 <!-- net/if.h -->
 <!-- IPv6 basic API -->
 <div class="defun">
 &mdash; Function: void <b>if_freenameindex</b> (<var>struct if_nameindex *ptr</var>)<var><a name="index-if_005ffreenameindex-1671"></a></var><br>
 <blockquote><p>This function frees the structure returned by an earlier call to
 <code>if_nameindex</code>.
 </p></blockquote></div>

    </body></html>
	<html lang="en">
	<head>
	<title>Interface Naming - The GNU C Library</title>
	<meta http-equiv="Content-Type" content="text/html">
	<meta name="description" content="The GNU C Library">
	<meta name="generator" content="makeinfo 4.13">
	<link title="Top" rel="start" href="index.html#Top">
	<link rel="up" href="Sockets.html#Sockets" title="Sockets">
	<link rel="prev" href="Socket-Addresses.html#Socket-Addresses" title="Socket Addresses">
	<link rel="next" href="Local-Namespace.html#Local-Namespace" title="Local Namespace">
	<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
	<!--
	This file documents the GNU C library.

	This is Edition 0.12, last updated 2007-10-27,
	of `The GNU C Library Reference Manual', for version
	2.8 (Sourcery G++ Lite 2011.03-41).

	Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002,
	2003, 2007, 2008, 2010 Free Software Foundation, Inc.

	Permission is granted to copy, distribute and/or modify this document
	under the terms of the GNU Free Documentation License, Version 1.3 or
	any later version published by the Free Software Foundation; with the
	Invariant Sections being ``Free Software Needs Free Documentation''
	and ``GNU Lesser General Public License'', the Front-Cover texts being
	``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A
	copy of the license is included in the section entitled "GNU Free
	Documentation License".

	(a) The FSF's Back-Cover Text is: ``You have the freedom to
	copy and modify this GNU manual. Buying copies from the FSF
	supports it in developing GNU and promoting software freedom.''-->
	<meta http-equiv="Content-Style-Type" content="text/css">
	<style type="text/css"><!--
	pre.display { font-family:inherit }
	pre.format { font-family:inherit }
	pre.smalldisplay { font-family:inherit; font-size:smaller }
	pre.smallformat { font-family:inherit; font-size:smaller }
	pre.smallexample { font-size:smaller }
	pre.smalllisp { font-size:smaller }
	span.sc { font-variant:small-caps }
	span.roman { font-family:serif; font-weight:normal; }
	span.sansserif { font-family:sans-serif; font-weight:normal; }
	--></style>
	<link rel="stylesheet" type="text/css" href="../cs.css">
	</head>
	<body>
	<div class="node">
	<a name="Interface-Naming"></a>
	<p>
	Next: <a rel="next" accesskey="n" href="Local-Namespace.html#Local-Namespace">Local Namespace</a>,
	Previous: <a rel="previous" accesskey="p" href="Socket-Addresses.html#Socket-Addresses">Socket Addresses</a>,
	Up: <a rel="up" accesskey="u" href="Sockets.html#Sockets">Sockets</a>
	<hr>
	</div>

	<h3 class="section">16.4 Interface Naming</h3>

	<p>Each network interface has a name. This usually consists of a few
	letters that relate to the type of interface, which may be followed by a
	number if there is more than one interface of that type. Examples
	might be <code>lo</code> (the loopback interface) and <code>eth0</code> (the first
	Ethernet interface).

	<p>Although such names are convenient for humans, it would be clumsy to
	have to use them whenever a program needs to refer to an interface. In
	such situations an interface is referred to by its <dfn>index</dfn>, which is
	an arbitrarily-assigned small positive integer.

	<p>The following functions, constants and data types are declared in the
	header file <samp><span class="file">net/if.h</span></samp>.

	<!-- net/if.h -->
	<div class="defun">
	— Constant: size_t <b>IFNAMSIZ</b><var><a name="index-IFNAMSIZ-1666"></a></var><br>
	<blockquote><p>This constant defines the maximum buffer size needed to hold an
	interface name, including its terminating zero byte.
	</p></blockquote></div>

	<!-- net/if.h -->
	<!-- IPv6 basic API -->
	<div class="defun">
	— Function: unsigned int <b>if_nametoindex</b> (<var>const char *ifname</var>)<var><a name="index-if_005fnametoindex-1667"></a></var><br>
	<blockquote><p>This function yields the interface index corresponding to a particular
	name. If no interface exists with the name given, it returns 0.
	</p></blockquote></div>

	<!-- net/if.h -->
	<!-- IPv6 basic API -->
	<div class="defun">
	— Function: char * <b>if_indextoname</b> (<var>unsigned int ifindex, char *ifname</var>)<var><a name="index-if_005findextoname-1668"></a></var><br>
	<blockquote><p>This function maps an interface index to its corresponding name. The
	returned name is placed in the buffer pointed to by <code>ifname</code>, which
	must be at least <code>IFNAMSIZ</code> bytes in length. If the index was
	invalid, the function's return value is a null pointer, otherwise it is
	<code>ifname</code>.
	</p></blockquote></div>

	<!-- net/if.h -->
	<!-- IPv6 basic API -->
	<div class="defun">
	— Data Type: <b>struct if_nameindex</b><var><a name="index-struct-if_005fnameindex-1669"></a></var><br>
	<blockquote><p>This data type is used to hold the information about a single
	interface. It has the following members:

	<dl>
	<dt><code>unsigned int if_index;</code><dd>This is the interface index.

	<br><dt><code>char *if_name</code><dd>This is the null-terminated index name.

	</dl>
	</p></blockquote></div>

	<!-- net/if.h -->
	<!-- IPv6 basic API -->
	<div class="defun">
	— Function: struct if_nameindex * <b>if_nameindex</b> (<var>void</var>)<var><a name="index-if_005fnameindex-1670"></a></var><br>
	<blockquote><p>This function returns an array of <code>if_nameindex</code> structures, one
	for every interface that is present. The end of the list is indicated
	by a structure with an interface of 0 and a null name pointer. If an
	error occurs, this function returns a null pointer.

	<p>The returned structure must be freed with <code>if_freenameindex</code> after
	use.
	</p></blockquote></div>

	<!-- net/if.h -->
	<!-- IPv6 basic API -->
	<div class="defun">
	— Function: void <b>if_freenameindex</b> (<var>struct if_nameindex *ptr</var>)<var><a name="index-if_005ffreenameindex-1671"></a></var><br>
	<blockquote><p>This function frees the structure returned by an earlier call to
	<code>if_nameindex</code>.
	</p></blockquote></div>

	</body></html>