856 lines
22 KiB
HTML
856 lines
22 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>pwrite()--Write to Descriptor with Offset</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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<!-- 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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<!-- 010308 JTROUS Creation date based on write, for V5R2, DCR 98686 -->
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<!-- 010703 JTROUS Add ERESTART, EINTR, V5R2, DCR 98686, Change -->
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<!-- CCSID restriction, SE01918, add dev/zero -->
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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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<!-- 020624 RTHEIS: Add fclear() and fclear64(), 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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<!-- 030730 VONBERGE: Add comment about qsys mbrs in text mode -->
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<!-- 050406 JTROUS: fix enums, no change flag, V5R4 -->
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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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<!-- 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>pwrite()--Write to Descriptor with Offset</h2>
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<div class="box" style="width: 60%;">
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<br>
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Syntax
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<pre>
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#include <unistd.h>
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ssize_t pwrite
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(int <em>file_descriptor</em>, const void <em>*buf</em>,
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size_t <em>nbyte</em>, off_t <em>offset</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>pwrite()</strong> function writes <em>nbyte</em> bytes from <em>
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buf</em> to the file associated with <em>file_descriptor</em>. The <em>
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offset</em> value defines the starting position in the file and the file
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pointer position is not changed.</p>
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<p>See <a href="write.htm">write()--Write to Descriptor</a> for more
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information relating to writing to a descriptor.</p>
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<p>The <em>offset</em> will also be ignored if <em>file_descriptor</em> refers
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to a descriptor obtained using the <strong>open()</strong> function with
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O_APPEND specified.</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>file_descriptor</em></strong></dt>
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<dd>(Input) The descriptor of the file to which the data is to be written.<br>
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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>(Input) A pointer to a buffer containing the data to be written.<br>
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<br>
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</dd>
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<dt><strong><em>nbyte</em></strong></dt>
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<dd>(Input) The size in bytes of the data to be written.<br>
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<br>
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</dd>
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<dt><strong><em>offset</em></strong></dt>
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<dd>(Input) The offset to the desired starting position in the file.</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>pwrite()</strong> was successful. The
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value returned is the number of bytes actually written. This number is less
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than or equal to <em>nbyte</em>.</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>pwrite()</strong> was not successful. The
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<em>errno</em> global variable is set to indicate the error.</td>
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</tr>
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</table>
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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>pwrite()</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#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 object would exceed the system allowed maximum size or the
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process soft file size limit.
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The file is a regular file, <em>nbyte</em> is greater than 0, and the
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starting offset is greater than or equal to 2 GB minus 2 bytes.</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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<p>The file system that the file resides in does not support large files, and
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the starting offset exceeds 2GB minus 2 bytes.
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This will also occur if the <em>offset</em> value is less than 0.</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#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><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#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#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#ENXIO">ENXIO</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#ERESTART">ERESTART</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#ETRUNC">ETRUNC</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#ESPIPE">ESPIPE</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>
|
||
|
|
</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>
|
||
|
|
|
||
|
|
<p>If interaction with a file server is required to access the object, <em>
|
||
|
|
errno</em> could also 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#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#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">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</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 align="left" valign="top">CPE3418 E</td>
|
||
|
|
<td align="left" 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>
|
||
|
|
<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>
|
||
|
|
<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>QSYS.LIB and Independent ASP QSYS.LIB File System Differences
|
||
|
|
|
||
|
|
<p>
|
||
|
|
For a physical file member opened in text mode, the <em>offset</em> must be equal to the current file position. Otherwise, this operation will fail with error code [EIO].
|
||
|
|
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<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>If the file specified is a save file, only complete records will be written
|
||
|
|
into the save file. A <strong>pwrite()</strong> request that does not provide
|
||
|
|
enough data to completely fill a save file record will cause the partial
|
||
|
|
record's data to be saved by the file system. The saved partial record will
|
||
|
|
then be combined with additional data on subsequent <strong>pwrite()</strong>'s
|
||
|
|
until a complete record may be written into the save file. If the save file is
|
||
|
|
closed prior to a saved partial record being written into the save file, then
|
||
|
|
the saved partial record is discarded, and the data in that partial record will
|
||
|
|
need to be written again by the application.</p>
|
||
|
|
|
||
|
|
<p>A successful <strong>pwrite()</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>
|
||
|
|
|
||
|
|
<p>You should be careful when writing end-of-file characters in the QSYS.LIB
|
||
|
|
and independent ASP QSYS.LIB file systems. For these file systems, end-of-file
|
||
|
|
characters are symbolic; that is, they are stored outside the file member.
|
||
|
|
However, some situations can result in actual, nonsymbolic end-of-file
|
||
|
|
characters being written to a member. These nonsymbolic end-of-file characters
|
||
|
|
could cause some tools or utilities to fail. For example:<br>
|
||
|
|
<br>
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>If you previously wrote an end-of-file character as the last character of a
|
||
|
|
member, do not continue to write data after that end-of-file character.
|
||
|
|
Continuing to write data will cause a nonsymbolic end-of-file to be written. As
|
||
|
|
a result, a compile of the member could fail.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If you previously wrote an end-of-file character as the last character of a
|
||
|
|
member, do not write other end-of-file characters preceding it in the file.
|
||
|
|
This will cause a nonsymbolic end-of-file to be written. As a result, a compile
|
||
|
|
of the member could fail.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If you previously used the integrated file system interface to manipulate a
|
||
|
|
member that contains an end-of-file character, avoid using other interfaces
|
||
|
|
(such as the Source Entry Utility or database reads and writes) to manipulate
|
||
|
|
the member. If you use other interfaces after using the integrated file system
|
||
|
|
interface, the end-of-file information will be lost.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
</ul>
|
||
|
|
</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 written 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 and writing to files with the Network File System relies on
|
||
|
|
byte-range locking to guarantee data integrity. To prevent data inconsistency,
|
||
|
|
use the <strong>fcntl()</strong> API to get and release these locks.</p>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>QFileSvr.400 File System Differences
|
||
|
|
|
||
|
|
<p>The largest buffer size allowed is 16 megabytes. If a larger buffer is
|
||
|
|
passed, the error EINVAL will be received.</p>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>For the file systems that do not support large files, <strong>
|
||
|
|
pwrite()</strong> will return [EINVAL] if the starting offset exceeds 2GB minus
|
||
|
|
2 bytes, regardless of how the file was opened. For the file systems that do
|
||
|
|
support large files, <strong>pwrite()</strong> will return [EFBIG] if the
|
||
|
|
starting offset exceeds 2GB minus 2 bytes and the file was not opened for large
|
||
|
|
file access.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>Using this function successfully on the /dev/null or /dev/zero character
|
||
|
|
special file results in a return value of the total number of bytes requested
|
||
|
|
to be written. No data is written to the /dev/null or /dev/zero character
|
||
|
|
special file. In addition, the change and modification times for the file are
|
||
|
|
updated.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If the write exceeds the process soft file size limit, signal SIFXFSZ is
|
||
|
|
issued.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If <em>file_descriptor</em> refers to a descriptor obtained using the
|
||
|
|
<strong>open()</strong> function with O_TEXTDATA and O_CCSID specified, the
|
||
|
|
file CCSID and open CCSID are not the same, and the converted data could expand
|
||
|
|
or contract, then the <em>offset</em> value must be 0.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If <em>file_descriptor</em> refers to a character special file, the <em>
|
||
|
|
offset</em> value is ignored.</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="fclear.htm">fclear()</a>--Write (Binary Zeros) to 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="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="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="send.htm">send()</a>--Send Data</li>
|
||
|
|
|
||
|
|
<li><a href="sendms.htm">sendmsg()</a>--Send Data or Descriptors or Both</li>
|
||
|
|
|
||
|
|
<li><a href="sendto.htm">sendto()</a>--Send Data</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 writes a specific number of bytes to a file:</p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <sys/types.h>
|
||
|
|
#include <sys/stat.h>
|
||
|
|
#include <fcntl.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <stdlib.h>
|
||
|
|
|
||
|
|
#define mega_string_len 1000000
|
||
|
|
|
||
|
|
main() {
|
||
|
|
char *mega_string;
|
||
|
|
int file_descriptor;
|
||
|
|
int ret;
|
||
|
|
off_t off=5;
|
||
|
|
char fn[]="write.file";
|
||
|
|
|
||
|
|
if ((mega_string = (char*) malloc(mega_string_len+off)) == NULL)
|
||
|
|
perror("malloc() error");
|
||
|
|
else if ((file_descriptor = creat(fn, S_IWUSR)) < 0)
|
||
|
|
perror("creat() error");
|
||
|
|
else {
|
||
|
|
memset(mega_string, '0', mega_string_len);
|
||
|
|
if ((ret = pwrite(file_descriptor, mega_string, mega_string_len, off)) == -1)
|
||
|
|
perror("pwrite() error");
|
||
|
|
else printf("pwrite() wrote %d bytes at offset %d\n", ret, off);
|
||
|
|
if (close(file_descriptor)!= 0)
|
||
|
|
perror("close() error");
|
||
|
|
if (unlink(fn)!= 0)
|
||
|
|
perror("unlink() error");
|
||
|
|
}
|
||
|
|
free(mega_string);
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<strong>Output:</strong>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
pwrite() wrote 1000000 bytes at offset 5
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
API introduced: V5R2
|
||
|
|
|
||
|
|
<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>
|
||
|
|
|