836 lines
21 KiB
HTML
836 lines
21 KiB
HTML
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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>fclear()--Write (Binary Zeros) to Descriptor</title>
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<!-- Begin Header Records -->
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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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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<!-- 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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<!-- Change History: -->
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<!-- 020410 RTHEIS Created V5R3, DCR 99096 -->
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<!-- 020618 EMIG Updates for NFS threadsafety, V5R3 -->
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<!-- 050325 JTROUS: fix enums, no change flag, V5R4 -->
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<!-- 050427 JTROUS: Add QNTC restriction, 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 --><!-- Edited by Kersten Feb 02 -->
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>fclear()--Write (Binary Zeros) to Descriptor</h2>
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<div class="box" style="width: 60%;">
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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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off_t fclear
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(int <em>file_descriptor</em>, off_t <em>nbyte</em>);
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</pre>
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<br>
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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
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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>fclear()</strong> function writes <em>nbyte</em> bytes
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of binary zeros to the file associated with the <em>file_descriptor</em>.
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<em>nbyte</em> should not be greater than INT_MAX (defined in the
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<<strong>limits.h</strong>> header file). If it is, [EINVAL] will be returned.
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If <em>nbyte</em> is zero,
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<strong>fclear()</strong> simply returns a value of zero without attempting any
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other action.</p>
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<p>If <em>file_descriptor</em> refers to a "regular file" (a stream file that
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can support positioning the file offset), <strong>fclear()</strong>
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begins writing binary zeros at the file offset associated with <em>file_descriptor</em>.
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A successful
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<strong>fclear()</strong> increments the file offset by the number of bytes written.
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If the incremented file offset is greater than the previous length of
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the file, the length of the file is set to the new file offset.
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An unsuccessful <strong>fclear()</strong> will not change the file offset.
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If the <em>file_descriptor</em> does not refer to a "regular file", [EINVAL] will be returned.</p>
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<p>If O_APPEND (defined in the <<strong>fcntl.h</strong>> header file) is
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set for the file, <strong>fclear()</strong> does <b>not</b> set the file offset to the end of
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the file before writing the output. Instead, it begins writing binary zeros at the current file
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offset associated with the <em>file_descriptor</em>.</p>
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<p>If <b>fclear()</b> is called such that <em>nbyte</em>
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plus the current file offset will cause the size of the file to exceed
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2GB minus 1 bytes when the file is <b>not</b> opened for large file access,
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the system allowed maximum file size when the file is opened for large file access,
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or the process soft file size limit, [EFBIG] will be returned.</p>
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<p>If <strong>fclear()</strong> is successful and <em>nbyte</em> is greater than
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zero, the change and modification times for the file are updated.</p>
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<p>If <em>file_descriptor</em> refers to a descriptor obtained using the
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<strong>open()</strong> function with O_TEXTDATA specified, binary zeros are written
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to the file assuming they are in textual form. The data (binary zeros) is
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converted from the code page of the application, job, or system, to the code page of the file as
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follows:</p>
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<ul>
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<li>Only simple conversions are performed. That is, if one byte of binary zeros does not
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convert to one byte of binary zeros then [ENOTSUP] is returned.
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<li>When clearing a physical file in the QSYS.LIB file system the <b>fclear()</b> should not
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be performed across a record boundary. If it is, [ETRUNC] will be returned.
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</li>
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</ul>
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<p>Note: The conversion of binary zeros will always result in binary zeros.</p>
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<p>There are some important considerations if O_CCSID was specified on the
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<strong>open()</strong>.</p>
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<ul>
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<li>If an <b>fclear()</b> is performed when there are partial characters
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buffered internally due to a previous <b>write()</b>, the <b>fclear()</b> will fail
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with the [ENOTSUP] error.<br><br>
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</li>
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<li>Because of the above consideration and because of the possible expansion or
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contraction of converted data, applications using the O_CCSID flag should avoid
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assumptions about data size and the current file offset.</li>
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</ul>
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<p>If O_TEXTDATA was not specified on the <strong>open()</strong>, binary zeros
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are written to the file without conversion. The application is responsible for
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handling the data.</p>
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<p><strong>Note:</strong> When the <b>fclear</b> completes successfully, the S_ISUID
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(set-user-ID) and S_ISGID (set-group-ID) bits of the file mode will be cleared.
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If the <b>fclear()</b> is unsuccessful, the bits are undefined.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>file_descriptor</strong></dt>
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<dd>(Input) The descriptor of the file to be cleared (write binary zeros).
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<br><br>
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</dd>
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<dt><strong>nbyte</strong></dt>
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<dd>(Input) Indicates the number of bytes to clear (write binary zeros).
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<br><br>
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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>No authorization is required.</p>
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<br>
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<h3>Return Value</h3>
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<table cellpadding="5">
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<!-- cols="10 90" -->
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<tr>
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<td align="left" valign="top"><em>value</em></td>
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<td align="left" valign="top"><strong>fclear()</strong> was successful. The
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return value is the number of bytes that have been
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successfully cleared. This number will be equal to <em>nbyte</em>.
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>-1</em></td>
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<td align="left" valign="top"><strong>fclear()</strong> was not successful. The
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<strong>fclear()</strong> was not able to clear all of the bytes requested.
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No indication is given as to how much data was successfully cleared. In addition,
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the file offset will remaind unchanged. The <em>errno</em> global variable is set
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to indicate the error.</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 Conditions</h3>
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<p>If <strong>fclear()</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#EBADF">EBADF</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#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#EFBIG">EFBIG</a>]</em></td>
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<td align="left" valign="top">
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<p>The size of the file would exceed 2GB minus 1 bytes when the file is <b>not</b>
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opened for large file access, the system allowed maximum file size when the file
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is opened for large file access, or the process soft file size limit.</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#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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</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#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#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#ENEWJRN">ENEWJRN</a>]</em></td>
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||
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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#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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<td align="left" valign="top">
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|
|
<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#ENOTSAFE">ENOTSAFE</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENXIO">ENXIO</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ERESTART">ERESTART</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ETRUNC">ETRUNC</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>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
<p>Additionally, if interaction with a file server is required to access the object,
|
||
|
|
<em>errno</em> could indicate one of the following errors:</p>
|
||
|
|
|
||
|
|
<table cellpadding="5">
|
||
|
|
<!-- cols="25 75" -->
|
||
|
|
<tr>
|
||
|
|
<th align="left" valign="bottom">Error condition</th>
|
||
|
|
<th align="left" valign="bottom">Additional information</th>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EADDRNOTAVAIL">EADDRNOTAVAIL</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ECONNABORTED">ECONNABORTED</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ECONNREFUSED">ECONNREFUSED</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ECONNRESET">ECONNRESET</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EHOSTDOWN">EHOSTDOWN</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EHOSTUNREACH">EHOSTUNREACH</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENETDOWN">ENETDOWN</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENETRESET">ENETRESET</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENETUNREACH">ENETUNREACH</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ETIMEDOUT">ETIMEDOUT</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EUNATCH">EUNATCH</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<br>
|
||
|
|
<h3>Error Messages</h3>
|
||
|
|
|
||
|
|
<p>The following messages may be sent from this function:</p>
|
||
|
|
|
||
|
|
<table width="100%" cellpadding="5">
|
||
|
|
<!-- cols="15 85" -->
|
||
|
|
<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 align="left" valign="top">CPF3CF2 E</td>
|
||
|
|
<td align="left" valign="top">Error(s) occurred during running of &1
|
||
|
|
API.</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">CPF9872 E</td>
|
||
|
|
<td align="left" valign="top">Program or service program &1 in library
|
||
|
|
&2 ended. Reason code &3.</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">CPFA081 E</td>
|
||
|
|
<td align="left" valign="top">Unable to set return value or error code.</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">CPFA0D4 E</td>
|
||
|
|
<td align="left" valign="top">File system error occurred. Error number
|
||
|
|
&1.</td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<br>
|
||
|
|
<h3><a name="USAGE_NOTES">Usage Notes</a></h3>
|
||
|
|
|
||
|
|
<ol>
|
||
|
|
<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>
|
||
|
|
<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>QFileSvr.400</li>
|
||
|
|
|
||
|
|
<li>Network File System</li>
|
||
|
|
|
||
|
|
</ul>
|
||
|
|
</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>QSYS.LIB and independent
|
||
|
|
ASP QSYS.LIB File System
|
||
|
|
Differences
|
||
|
|
|
||
|
|
<p>This function will fail with error code [ENOTSAFE] if the object on which
|
||
|
|
this function is operating is a save file and multiple threads exist in the
|
||
|
|
job.</p>
|
||
|
|
|
||
|
|
<p>An <b>fclear()</b> request should not be done on a save file. If it is,
|
||
|
|
unpredictable results may occur.</p>
|
||
|
|
|
||
|
|
<p>A successful <strong>fclear()</strong> updates the change, modification, and
|
||
|
|
access times for a database member using the normal rules that apply to
|
||
|
|
database files. At most, the access time is updated once per day.</p>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
|
||
|
|
<li>QOPT File System Differences
|
||
|
|
|
||
|
|
<p>The change and modification times of the file are updated when the file is
|
||
|
|
closed.</p>
|
||
|
|
|
||
|
|
<p>When writing to files on volumes formatted in Universal Disk Format (UDF),
|
||
|
|
byte locks on the range being cleared are ignored.</p>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>Network File System Differences
|
||
|
|
|
||
|
|
<p>Local access to remote files through the Network File System may produce
|
||
|
|
unexpected results due to conditions at the server. Once a file is open,
|
||
|
|
subsequent requests to perform operations on the file can fail because file
|
||
|
|
attributes are checked at the server on each request. If permissions on the
|
||
|
|
file are made more restrictive at the server or the file is unlinked or made
|
||
|
|
unavailable by the server for another client, your operation on an open file
|
||
|
|
descriptor will fail when the local Network File System receives these updates.
|
||
|
|
The local Network File System also impacts operations that retrieve file
|
||
|
|
attributes. Recent changes at the server may not be available at your client
|
||
|
|
yet, and old values may be returned from operations (several options on the Add
|
||
|
|
Mounted File System (ADDMFS) command determine the time between refresh
|
||
|
|
operations of local data).</p>
|
||
|
|
|
||
|
|
<p>Reading, writing, and clearing of files with the Network File System relies on
|
||
|
|
byte-range locking to guarantee data integrity. To prevent data inconsistency,
|
||
|
|
use the <a href="fcntl.htm">fcntl()</a> API to get and release these locks.</p>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>QFileSvr.400 File System Differences
|
||
|
|
|
||
|
|
<p>This file system does not support <strong>fclear()</strong> or
|
||
|
|
<strong>fclear64()</strong>, [ENOTSUP] will be returned.</p>
|
||
|
|
</li>
|
||
|
|
<li><img src="delta.gif" alt="Start of change">QNTC File System Differences
|
||
|
|
|
||
|
|
<p>This file system does not support <strong>fclear()</strong> or
|
||
|
|
<strong>fclear64()</strong>, [ENOTSUP] will be returned.
|
||
|
|
<img src="deltaend.gif" alt="End of change"></p></li>
|
||
|
|
<li>File System Differences
|
||
|
|
|
||
|
|
<p>File systems other than "root" (/), QOpenSys, user-defined,
|
||
|
|
<img src="delta.gif" alt="Start of change">QNTC and QFileSvr.400
|
||
|
|
<img src="deltaend.gif" alt="End of change">
|
||
|
|
will be restricted
|
||
|
|
to doing <b>fclear()</b>s no larger than 2GB minus 1 bytes. If this rule
|
||
|
|
is violated [EINVAL] will be returned. </p></li>
|
||
|
|
|
||
|
|
<li>For the file systems that do not support large files,
|
||
|
|
<strong>fclear()</strong> will return [EINVAL] if <em>nbyte</em>
|
||
|
|
plus the file offset exceeds 2GB minus 1 bytes, regardless of how the file was opened.
|
||
|
|
For the file systems
|
||
|
|
that do support large files, <strong>fclear()</strong> will return [EFBIG] if
|
||
|
|
<em>nbyte</em>
|
||
|
|
plus the file offset exceeds 2GB minus 1 bytes and the file was not opened for
|
||
|
|
large file access.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If the <b>fclear()</b> exceeds the
|
||
|
|
process soft file size limit, signal SIFXFSZ is issued.</li>
|
||
|
|
|
||
|
|
</ol>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Related Information</h3>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>The <<strong>fcntl.h</strong>> file (see <a href="unix13.htm">Header
|
||
|
|
Files for UNIX-Type Functions</a>)
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>The <<strong>unistd.h</strong>> file (see <a href="unix13.htm">Header
|
||
|
|
Files for UNIX-Type Functions</a>)
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="creat.htm">creat()</a>--Create or Rewrite File
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="dup.htm">dup()</a>--Duplicate Open File Descriptor
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="dup2.htm">dup2()</a>--Duplicate Open File Descriptor to Another
|
||
|
|
Descriptor
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="fclear64.htm">fclear64()</a>--Write (Binary Zeros) to
|
||
|
|
Descriptor (Large File Enabled)
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="fcntl.htm">fcntl()</a>--Perform File Control Command
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ftruncat.htm">ftruncate()</a>--Truncate File
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ftrunc64.htm">ftruncate64()</a>--Truncate File (Large File Enabled)
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ioctl.htm">ioctl()</a>--Perform I/O Control Request
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="lseek.htm">lseek()</a>--Set File Read/Write Offset
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="open.htm">open()</a>--Open File
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href=
|
||
|
|
"pread.htm">pread()</a>--Read from Descriptor with Offset
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="pread64.htm">pread64()</a>--Read from Descriptor with Offset
|
||
|
|
(large file enabled)
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="pwrite.htm">pwrite()</a>--Write to Descriptor with Offset
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="pwrite64.htm">pwrite64()</a>--Write to Descriptor with Offset
|
||
|
|
(large file enabled)
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="read.htm">read()</a>--Read from Descriptor
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="readv.htm">readv()</a>--Read from Descriptor Using Multiple
|
||
|
|
Buffers
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="write.htm">write()</a>--Write to Descriptor
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="writev.htm">writev()</a>--Write to Descriptor Using Multiple
|
||
|
|
Buffers
|
||
|
|
</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 clears a specific number of bytes in a file:</p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
|
||
|
|
main() {
|
||
|
|
int fileDescriptor;
|
||
|
|
off_t ret;
|
||
|
|
int oflags = O_CREAT | O_RDWR;
|
||
|
|
mode_t mode = S_IRUSR | S_IWUSR | S_IXUSR;
|
||
|
|
|
||
|
|
if ((fileDescriptor = open("foo", oflags, mode)) < 0)
|
||
|
|
perror("open() error");
|
||
|
|
else {
|
||
|
|
if ((ret = fclear(fileDescriptor, 10)) == -1)
|
||
|
|
perror("fclear() error");
|
||
|
|
else printf("fclear() cleared %d bytes.\n", ret);
|
||
|
|
if (close(fileDescriptor)!= 0)
|
||
|
|
perror("close() error");
|
||
|
|
if (unlink("foo")!= 0)
|
||
|
|
perror("unlink() error");
|
||
|
|
}
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<p><strong>Output:</strong></p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
fclear() cleared 10 bytes.
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<p>API introduced: V5R3</p>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<table align="center" 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>
|
||
|
|
</body>
|
||
|
|
</html>
|
||
|
|
|