135 lines
4.9 KiB
HTML
135 lines
4.9 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>ftruncate64()--Truncate File (Large File Enabled)</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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<!-- 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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<!-- 011022 JTROUS Changes from API Review 1, V5R2 -->
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<!-- 020514 JET This file has undergone html cleanup -->
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<!-- 030217 JTROUS : Add words about offset not updated -->
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<!-- 050415 JTROUS Changes from API Review 1, V5R4, no change flag -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!--End Header Records --><!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>ftruncate64()--Truncate File (Large File Enabled)</h2>
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<div class="box" style="width: 70%;">
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<br>
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Syntax<br>
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<pre>
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#include <unistd.h>
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int ftruncate64(int <em>file_descriptor</em>, off64_t <em>length</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>ftruncate64()</strong> function truncates the file indicated by
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the open file descriptor <em>file_descriptor</em> to the indicated <em>
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length</em>. <em>file_descriptor</em> must be a "regular file" that is open for
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writing. (A regular file is a stream file that can support positioning the file
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offset.) If the file size exceeds <em>length</em>, any extra data is discarded.
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If the file size is smaller than <em>length</em>, the file is extended and
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filled with binary zeros to the indicated length. (In the QSYS.LIB and
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independent ASP QSYS.LIB file systems, blanks are used instead of zeros to pad
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records after a member is extended.)
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The <strong>ftruncate64()</strong> function does not modify the current file offset
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for any open file descriptions associated with the file.
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</p>
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<p><strong>ftruncate64()</strong> is enabled for large files. It is capable of
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operating on files larger than 2GB minus 1 byte as long as the file has been
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opened by either of the following:</p>
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<ul compact>
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<li>Using the <strong>open64()</strong> function (see <a href="open64.htm">
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open64()--Open File (Large File Enabled)</a>).</li>
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<li>Using the <strong>open()</strong> function (see <a href="open.htm">
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open()--Open File</a>) with the O_LARGEFILE flag set in the oflag
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parameter.</li>
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</ul>
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<p>If <strong>ftruncate64()</strong> completes successfully, it marks the
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change time and modification times of the file. If <strong>
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ftruncate64()</strong> is not successful, the file is unchanged.</p>
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<p>For additional information about parameters, authorities, error conditions,
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and examples, see <a href="ftruncat.htm">ftruncate()--Truncate File</a>.</p>
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<br>
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<h3><a name="usage_notes">Usage Notes</a></h3>
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<ol type="1">
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<li>For file systems that do support large files, this function will fail with
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the [EFBIG] error if the <em>length</em> specified is greater than 2GB minus 1
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byte and O_LARGEFILE is not set in the oflag.<br><br>
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</li>
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<li>For file systems that do not support large files, this function will fail
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with the [EINVAL] error if the <em>length</em> specified is greater than 2GB
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minus 1 byte.<br><br>
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</li>
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<li>QFileSvr.400 File System Differences
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<p>Although QFileSvr.400 does not support large files, it will return [EFBIG]
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if the <em>length</em> specified is greater than 2GB minus 1 byte.</p>
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</li>
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<li>When you develop in C-based languages, the prototypes for the 64-bit APIs
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are normally hidden. To use the <strong>ftruncate64()</strong> API and the
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off64_t data type, you must compile the source with _LARGE_FILE_API
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defined.<br><br>
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</li>
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<li>All of the usage notes for <strong>ftruncate()</strong> apply to <strong>
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ftruncate64()</strong>. See <a href="ftruncat.htm#HDRFTRNUSG">Usage Notes</a>
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in the <strong>ftruncate()</strong> API.</li>
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</ol>
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<br>
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<hr>
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API introduced: V4R4
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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