698 lines
15 KiB
HTML
698 lines
15 KiB
HTML
<!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>readlink()--Read Value of Symbolic Link</title>
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<!-- Begin Header Records ========================================== -->
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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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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<!-- Change History: -->
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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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<!--End Header Records -->
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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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<a name="Top_Of_Page"></a>
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<!-- 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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<h2>readlink()--Read Value of Symbolic Link</h2>
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<div class="box" style="width: 65%;">
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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 readlink(const char <em>*path</em>, char <em>*buf</em>, size_t <em>bufsiz</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>readlink()</strong> function places the contents of the symbolic
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link <em>path</em> in the buffer <em>buf</em>. The size of the buffer is set by
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<em>bufsiz</em>. The contents of the returned buffer do not include a
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terminating NULL. When <em>bufsiz</em> is 0, the number of bytes contained in
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the symbolic link is returned and the buffer is unchanged.</p>
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<p>If the buffer is too small to contain the contents of the symbolic link, the
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contents are truncated to the size of the buffer (<em>bufsiz</em>).</p>
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<p>A successful <strong>readlink()</strong>, where <em>bufsiz</em> is greater
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than zero, sets the access time of the symbolic link.</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>path</em></strong></dt>
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<dd>(Input) A pointer to the null-terminated path name of the symbolic link.
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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="readlinku.htm">QlgReadlink()</a>--Read Value of Symbolic Link
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for a description and an example of supplying the <em>path</em> in any
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CCSID.</p>
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<br>
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</dd>
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<dt><strong><em>buf</em></strong></dt>
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<dd>(Output) A pointer to the area in which the contents of the link should be
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stored.
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<p>This parameter will be returned in the CCSID currently in effect for the
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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.</p>
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<br>
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</dd>
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<dt><strong>bufsiz</strong></dt>
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<dd>(Input) The size of <em>buf</em> in bytes.</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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<strong><a name="TBLAREADLN">Authorization required for readlink()</a></strong>
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<table border width="80%">
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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 path name
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preceding the object</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">Object</td>
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<td align="center" valign="top">None</td>
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<td align="left" valign="top">None</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>value</em></dt>
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<dd><strong>readlink()</strong> was successful.
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<p>When <em>bufsiz</em> is greater than zero, the value returned is the number
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of bytes placed in the buffer. When <em>bufsiz</em> is zero, the value returned
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is the number of bytes contained in the symbolic link. The buffer is not
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changed.</p>
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<p>If the return value is equal to <em>bufsiz</em>, the entire contents of the
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symbolic link may not have been returned. You can determine the size of the
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contents of the symbolic link by using either <strong>lstat()</strong> or
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<strong>readlink()</strong> with a zero value for <em>bufsiz</em>.</p>
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</dd>
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<dt><em>-1</em></dt>
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<dd><strong>readlink()</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>readlink()</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#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#EINTR">EINTR</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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<p>For example, the named file is not a symbolic link.</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#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#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#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#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#ENOTAVAIL">ENOTAVAIL</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#ENOTDIR">ENOTDIR</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#ENOTSAFE">ENOTSAFE</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#ENOTSUP">ENOTSUP</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#EROOBJ">EROOBJ</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#ESTALE">ESTALE</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, the file
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may have been deleted at the server.</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#EUNKNOWN">EUNKNOWN</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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</table>
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<p>If interaction with a file server is required to access the object, <em>
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errno</em> could indicate one of the following errors:</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#EADDRNOTAVAIL">EADDRNOTAVAIL</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#ECONNABORTED">ECONNABORTED</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#ECONNREFUSED">ECONNREFUSED</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#ECONNRESET">ECONNRESET</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#EHOSTDOWN">EHOSTDOWN</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#EHOSTUNREACH">EHOSTUNREACH</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#ENETDOWN">ENETDOWN</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#ENETRESET">ENETRESET</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#ENETUNREACH">ENETUNREACH</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#ESTALE">ESTALE</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, the file
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may have been deleted at the server.</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#ETIMEDOUT">ETIMEDOUT</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#EUNATCH">EUNATCH</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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</table>
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<br>
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<br>
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<h3>Error Messages</h3>
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<p>The following messages may be sent from this function:</p>
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<table width="100%">
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<tr>
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<th align="left" valign="top">Message ID</th>
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<th align="left" valign="top">Error Message Text</th>
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</tr>
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<tr>
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<td width="15%" valign="top">CPE3418 E</td>
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|
<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>
|
|
<br>
|
|
<h3><a name="USAGE_NOTES">Usage Notes</a></h3>
|
|
|
|
<ol type="1">
|
|
<li>
|
|
<p>This function will fail with error code [ENOTSAFE] when all the following
|
|
conditions are true:</p>
|
|
|
|
<ul>
|
|
<li>Where multiple threads exist in the job.</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:
|
|
|
|
<ul>
|
|
<li>"Root" (/)</li>
|
|
|
|
<li>QOpenSys</li>
|
|
|
|
<li>User-defined</li>
|
|
|
|
<li>Network File System</li>
|
|
|
|
<li>QFileSvr.400</li>
|
|
</ul>
|
|
|
|
<br>
|
|
</li>
|
|
</ul>
|
|
|
|
<br>
|
|
</li>
|
|
|
|
<li>The following file systems do not support <strong>readlink()</strong>.</p>
|
|
|
|
<ul>
|
|
<li>QSYS.LIB</li>
|
|
|
|
<li>Independent ASP QSYS.LIB</li>
|
|
|
|
<li>QDLS</li>
|
|
|
|
<li>QOPT</li>
|
|
|
|
<li>QNetWare</li>
|
|
|
|
<li>QNTC</li>
|
|
</ul>
|
|
</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>)</li>
|
|
|
|
<li><a href="lstat.htm">lstat()</a>--Get File or Link Information</li>
|
|
|
|
<li><a href="readlinku.htm">QlgReadlink()</a>--Read Value of Symbolic Link</li>
|
|
|
|
<li><a href="stat.htm">stat()</a>--Get File Information</li>
|
|
|
|
<li><a href="symlink.htm">symlink()</a>--Make Symbolic Link</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>readlink()</strong>:</p>
|
|
|
|
<pre>
|
|
#include <unistd.h>
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <fcntl.h>
|
|
|
|
main() {
|
|
char fn[]="readlink.file";
|
|
char sl[]="readlink.symlink";
|
|
char buf[30];
|
|
int file_descriptor;
|
|
|
|
if ((file_descriptor = creat(fn, S_IWUSR)) < 0)
|
|
perror("creat() error");
|
|
else {
|
|
close(file_descriptor);
|
|
if (symlink(fn, sl) != 0)
|
|
perror("symlink() error");
|
|
else {
|
|
if (readlink(sl, buf, sizeof(buf)) < 0)
|
|
perror("readlink() error");
|
|
else printf("readlink() returned '%s' for '%s'\n", buf, sl);
|
|
|
|
unlink(sl);
|
|
}
|
|
unlink(fn);
|
|
}
|
|
}
|
|
</pre>
|
|
|
|
<p><strong>Output:</strong></p>
|
|
|
|
<pre>
|
|
readlink() returned 'readlink.file' for 'readlink.symlink'
|
|
</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>
|
|
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