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16 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>link()--Create Link to File</title>
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<!-- Begin Header Records ========================================== -->
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Change History: -->
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<!-- YYMMDD USERID Change description -->
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<!-- file cleaned -->
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<!-- Unix2 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 -->
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<!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 -->
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<!-- 010320 JTROUS Include Journal ERRNOs, should have in V5R1 -->
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<!-- 011022 JTROUS Changes from API Review 1, V5R2 -->
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<!-- 020618 EMIG: updated for NFS threadsafety, V5R3 -->
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<!-- 0205?? JET This file has undergone html cleanup -->
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<!-- 020719 MFENLON: updated for QFileSvr.400 threadsafety, V5R3 -->
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<!-- 050404 JTROUS: fix enums, no change flag, V5R4 -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!--End Header Records --><!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>link()--Create Link to File</h2>
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<div class="box" style="width: 70%;">
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<br>
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Syntax<br>
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<pre>
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#include <unistd.h>
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int link(const char <em>*existing</em>, const char <em>*new</em>);
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</pre>
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Service Program Name: QP0LLIB1<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Conditional; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>link()</strong> function provides an alternative path name for
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the existing file, so that the file can be accessed by either the existing name
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or the new name. <strong>link()</strong> creates a link with a path name <em>
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new</em> to an existing file whose path name is <em>existing</em>. The link can
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be stored in the same directory as the original file or in a different
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directory.</p>
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<p>The <strong>link()</strong> function creates a hard link, which guarantees
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the existence of a file even after the original path name has been removed.</p>
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<p>If <strong>link()</strong> successfully creates the link, it increments the
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<em>link count</em> of the file. The link count indicates how many links there
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are to the file. If <strong>link()</strong> fails for some reason, the link
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count is not incremented.</p>
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<p>If the <em>existing</em> argument names a symbolic link, <strong>
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link()</strong> creates a link that refers to the file that results from
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resolving the path name contained in the symbolic link. If <em>new</em> names a
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symbolic link, <strong>link()</strong> fails and sets <em>errno</em> to
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[EEXIST].</p>
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<p>A successful link updates the change time of the file, and the change time
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and modification time of the directory that contains <em>new</em> (parent
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directory).</p>
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<p>If the file is checked out by another user (a user profile other than the
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user profile of the current job), <strong>link()</strong> fails with the
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[EBUSY] error.</p>
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<p>Links created by this function are not allowed to cross file systems. For
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example, you cannot create a link to a file in the QOpenSys directory from the
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"root" (/) directory.</p>
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<p>Links are not allowed to directories. If <em>existing</em> names a
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directory, <strong>link()</strong> fails and sets <em>errno</em> to
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[EPERM].</p>
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<p>A job must have access to a file to link to it.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong><em>existing</em></strong></dt>
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<dd>(Input) A pointer to a null-terminated path name naming an existing file to
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which a new link is to be created.
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<p>This parameter is assumed to be represented in the CCSID (coded character
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set identifier) currently in effect for the job. If the CCSID of the job is
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65535, this parameter is assumed to be represented in the default CCSID of the
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job.</p>
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<p>See <a href="linku.htm">QlgLink()--Create Link to File</a> for a description
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and an example of supplying the <em>existing</em> in any CCSID.</p>
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<br>
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</dd>
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<dt><strong><em>new</em></strong></dt>
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<dd>(Input) A pointer to a null-terminated path name that is the name of the
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new link.<br>
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<br>
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<p>This parameter is assumed to be represented in the CCSID currently in effect
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for the job. If the CCSID of the job is 65535, this parameter is assumed to be
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represented in the default CCSID of the job. The new link name is assumed to be
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represented in the language and country or region currently in effect for the
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job.</p>
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<p>See <a href="linku.htm">QlgLink()--Create Link to File</a> for a description
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and an example of supplying the <em>new</em> in any CCSID.</p>
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</dd>
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</dl>
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<br>
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<h3>Authorities</h3>
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<p><strong>Note:</strong> Adopted authority is not used.</p>
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<p><strong><a name="TBLALINK">Authorization Required for
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link()</a></strong></p>
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<table border>
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<tr>
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<th align="left" valign="bottom">Object Referred to</th>
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<th align="center" valign="bottom">Authority Required</th>
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<th align="left" valign="bottom">errno</th>
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</tr>
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<tr>
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<td align="left" valign="top" width="75%">Each directory in the <em>
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existing</em> path name that precedes the object being linked to</td>
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<td align="center" valign="top" width="15%">*X</td>
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<td align="left" valign="top" width="10%">EACCES</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>Existing</em> object</td>
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<td align="center" valign="top">*OBJEXIST</td>
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<td align="left" valign="top">EACCES</td>
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</tr>
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<tr>
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<td align="left" valign="top">Each directory in the <em>new</em> path name that
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precedes the object being linked to</td>
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<td align="center" valign="top">*X</td>
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<td align="left" valign="top">EACCES</td>
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</tr>
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<tr>
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<td align="left" valign="top">Parent directory of the new link</td>
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<td align="center" valign="top">*WX</td>
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<td align="left" valign="top">EACCES</td>
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</tr>
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</table>
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<br>
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<h3>Return Value</h3>
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<dl compact>
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<dt><em>0</em></dt>
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<dd><strong>link()</strong> was successful.</dd>
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<dt><em>-1</em></dt>
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<dd><strong>link()</strong> was not successful. The <em>errno</em> global
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variable is set to indicate the error.</dd>
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</dl>
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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>link()</strong> is not successful, <em>errno</em> usually
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indicates one of the following errors. Under some conditions, <em>errno</em>
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could indicate an error other than those listed here.</p>
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<table cellpadding="5">
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<!-- cols="25 75" -->
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<tr>
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<th align="left" valign="bottom">Error condition</th>
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<th align="left" valign="bottom">Additional information</th>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EACCES">EACCES</a>]</em></td>
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<td align="left" valign="top">
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<p>If you are accessing a remote file through the Network File System, update
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operations to file permissions at the server are not reflected at the client
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until updates to data that is stored locally by the Network File System take
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place. (Several options on the Add Mounted File System (ADDMFS) command
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determine the time between refresh operations of local data.) Access to a
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remote file may also fail due to different mappings of user IDs (UID) or group
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IDs (GID) on the local and remote systems.</p>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EAGAIN">EAGAIN</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EBADFID">EBADFID</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EBADNAME">EBADNAME</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EBUSY">EBUSY</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ECONVERT">ECONVERT</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EDAMAGE">EDAMAGE</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EEXIST">EEXIST</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EFAULT">EFAULT</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EFILECVT">EFILECVT</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EINVAL">EINVAL</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EIO">EIO</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EISDIR">EISDIR</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EJRNDAMAGE">EJRNDAMAGE</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EJRNENTTOOLONG">EJRNENTTOOLONG</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EJRNINACTIVE">EJRNINACTIVE</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EJRNRCVSPC">EJRNRCVSPC</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ELOOP">ELOOP</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EMLINK">EMLINK</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENAMETOOLONG">ENAMETOOLONG</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENEWJRN">ENEWJRN</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENEWJRNRCV">ENEWJRNRCV</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENOENT">ENOENT</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENOMEM">ENOMEM</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENOSPC">ENOSPC</a>]</em></td>
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<td align="left" valign="top">
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</td>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#ENOSYS">ENOSYS</a>]</em></td>
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|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#ENOTAVAIL">ENOTAVAIL</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#ENOTDIR">ENOTDIR</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#ENOTSAFE">ENOTSAFE</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#ENOTSUP">ENOTSUP</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#EPERM">EPERM</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
<p>Links to directories are not supported.</p>
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#EROOBJ">EROOBJ</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#ESTALE">ESTALE</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
<p>If you are accessing a remote file through the Network File System, the file
|
||
|
may have been deleted at the server.</p>
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#EUNKNOWN">EUNKNOWN</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
|
||
|
|
||
|
<tr>
|
||
|
<td align="left" valign="top">
|
||
|
<em>[<a href="unix14.htm#EXDEV">EXDEV</a>]</em></td>
|
||
|
|
||
|
<td align="left" valign="top">
|
||
|
|
||
|
</td>
|
||
|
</tr>
|
||
|
</table>
|
||
|
|
||
|
<br>
|
||
|
<br>
|
||
|
<h3>Error Messages</h3>
|
||
|
|
||
|
<p>The following messages may be sent from this function:</p>
|
||
|
|
||
|
<table width="100%">
|
||
|
<tr>
|
||
|
<th align="left" valign="top">Message ID</th>
|
||
|
<th align="left" valign="top">Error Message Text</th>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td width="15%" valign="top">CPE3418 E</td>
|
||
|
<td width="85%" valign="top">Possible APAR condition or hardware failure.</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td valign="top">CPFA0D4 E</td>
|
||
|
<td valign="top">File system error occurred. Error number &1.</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td valign="top">CPF3CF2 E</td>
|
||
|
<td valign="top">Error(s) occurred during running of &1 API.</td>
|
||
|
</tr>
|
||
|
|
||
|
<tr>
|
||
|
<td valign="top">CPF9872 E</td>
|
||
|
<td valign="top">Program or service program &1 in library &2 ended.
|
||
|
Reason code &3.</td>
|
||
|
</tr>
|
||
|
</table>
|
||
|
|
||
|
<br>
|
||
|
<h3><a name="usage_notes">Usage Notes</a></h3>
|
||
|
|
||
|
<ol type="1">
|
||
|
<li>This function will fail with error code [ENOTSAFE] when all the following
|
||
|
conditions are true:<br>
|
||
|
<br>
|
||
|
<ul>
|
||
|
<li>Where multiple threads exist in the job.<br>
|
||
|
</li>
|
||
|
|
||
|
<li>The object on which this function is operating resides in a file system
|
||
|
that is not threadsafe. Only the following file systems are threadsafe for this
|
||
|
function:<br>
|
||
|
<br>
|
||
|
<ul>
|
||
|
<li>"Root" (/)</li>
|
||
|
|
||
|
<li>QOpenSys</li>
|
||
|
|
||
|
<li>User-defined</li>
|
||
|
|
||
|
<li>QNTC</li>
|
||
|
|
||
|
<li>QSYS.LIB</li>
|
||
|
|
||
|
<li>Independent ASP QSYS.LIB</li>
|
||
|
|
||
|
<li>QOPT</li>
|
||
|
|
||
|
<li>Network File System</li>
|
||
|
|
||
|
<li>QFileSvr.400</li>
|
||
|
</ul>
|
||
|
</li>
|
||
|
</ul>
|
||
|
|
||
|
<br>
|
||
|
</li>
|
||
|
|
||
|
<li>The <strong>link()</strong> function should be used sparingly to avoid
|
||
|
potential performance degradation. The greater the number of hard links to an
|
||
|
object, the more time it will take to change the attributes of the object.<br><br>
|
||
|
</li>
|
||
|
|
||
|
<li>The following file systems do not support <strong>link()</strong>:</p>
|
||
|
|
||
|
<ul>
|
||
|
<li>QSYS.LIB</li>
|
||
|
|
||
|
<li>Independent ASP QSYS.LIB</li>
|
||
|
|
||
|
<li>QDLS</li>
|
||
|
|
||
|
<li>QOPT</li>
|
||
|
|
||
|
<li>QFileSvr.400</li>
|
||
|
|
||
|
<li>QNetWare</li>
|
||
|
|
||
|
<li>QNTC</li>
|
||
|
</ul>
|
||
|
|
||
|
<p>If <strong>link()</strong> is used in any of these file systems, a [ENOSYS]
|
||
|
error is returned.</p>
|
||
|
</li>
|
||
|
</ol>
|
||
|
|
||
|
<br>
|
||
|
<h3>Related Information</h3>
|
||
|
|
||
|
<ul>
|
||
|
<li>The <<strong>unistd.h</strong>> file (see <a href="unix13.htm">Header
|
||
|
Files for UNIX-Type Functions</a>)<br>
|
||
|
</li>
|
||
|
|
||
|
<li><a href="linku.htm">QlgLink()</a>--Create Link to File<br>
|
||
|
</li>
|
||
|
|
||
|
<li><a href="renamefs.htm">rename()</a>--Rename File or Directory<br>
|
||
|
</li>
|
||
|
|
||
|
<li><a href="unlink.htm">unlink()</a>--Remove Link to File</li>
|
||
|
</ul>
|
||
|
|
||
|
<br>
|
||
|
<h3>Example</h3>
|
||
|
|
||
|
<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
|
||
|
for information pertaining to code examples.</p>
|
||
|
|
||
|
<p>The following example uses <strong>link()</strong>:</p>
|
||
|
|
||
|
<pre>
|
||
|
#include <stdio.h>
|
||
|
#include <unistd.h>
|
||
|
#include <sys/types.h>
|
||
|
#include <sys/stat.h>
|
||
|
#include <fcntl.h>
|
||
|
#include <stdlib.h>
|
||
|
|
||
|
|
||
|
main()
|
||
|
{
|
||
|
char fn[]="link.example.file";
|
||
|
char ln[]="link.example.link";
|
||
|
int file_descriptor;
|
||
|
struct stat info;
|
||
|
|
||
|
if ((file_descriptor = creat(fn, S_IWUSR)) < 0)
|
||
|
perror("creat() error");
|
||
|
else {
|
||
|
close(file_descriptor);
|
||
|
puts("before link()");
|
||
|
stat(fn,&info);
|
||
|
printf(" number of links is %hu\n",info.st_nlink);
|
||
|
if (link(fn, ln) != 0) {
|
||
|
perror("link() error");
|
||
|
unlink(fn);
|
||
|
}
|
||
|
else {
|
||
|
puts("after link()");
|
||
|
stat(fn,&info);
|
||
|
printf(" number of links is %hu\n",info.st_nlink);
|
||
|
unlink(ln);
|
||
|
puts("after first unlink()");
|
||
|
stat(fn,&info);
|
||
|
printf(" number of links is %hu\n",info.st_nlink);
|
||
|
unlink(fn);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
</pre>
|
||
|
|
||
|
<p><strong>Output:</strong></p>
|
||
|
|
||
|
<pre>
|
||
|
before link()
|
||
|
number of links is 1
|
||
|
after link()
|
||
|
number of links is 2
|
||
|
after first unlink()
|
||
|
number of links is 1
|
||
|
</pre>
|
||
|
|
||
|
<br>
|
||
|
<hr>
|
||
|
API introduced: V3R1
|
||
|
|
||
|
<hr>
|
||
|
<center>
|
||
|
<table cellpadding="2" cellspacing="2">
|
||
|
<tr align="center">
|
||
|
<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
|
||
|
"unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td>
|
||
|
</tr>
|
||
|
</table>
|
||
|
</center>
|
||
|
</body>
|
||
|
</html>
|
||
|
|