1176 lines
31 KiB
HTML
1176 lines
31 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>write()--Write to Descriptor</title>
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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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<!-- Begin Header Records --><!-- 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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<!-- 010307 JTROUS Change to xref pread, pread64, pwrite, -->
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<!-- pwrite64 for V5R2, DCR 98686, also include -->
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<!-- changes from 98391, first PASE I0 for V5R2 -->
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<!-- 010320 JTROUS Include Journal ERRNOs, should have in V5R1 -->
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<!-- 010703 JTROUS Add ERESTART, EINTR, V5R2, DCR 98686, add dev/zero-->
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<!-- 011022 JTROUS Changes from API Review 1, V5R2 -->
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<!-- 020510 RTHEIS Add fclear() & fclear64() APIs, V5R3 -->
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<!-- 020618 EMIG: updated for NFS threadsafety, V5R3 -->
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<!-- 0206?? JET This file has undergone html cleanup -->
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<!-- 020718 MFENLON: updated for QFileSvr.400 threadsafety, V5R3 -->
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<!-- End Header Records -->
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<!-- Edited by Kersten Feb 02 -->
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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>write()--Write to Descriptor</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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ssize_t write
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(int <em>file_descriptor</em>, const void <em>*buf</em>, size_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 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>write()</strong> function writes <em>nbyte</em> bytes from <em>
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buf</em> to the file or socket associated with <em>file_descriptor</em>. <em>
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nbyte</em> should not be greater than INT_MAX (defined in the
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<<strong>limits.h</strong>> header file). If <em>nbyte</em> is zero,
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<strong>write()</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) or any other type of file on which the
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job can do an <strong>lseek()</strong> operation, <strong>write()</strong>
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begins writing at the file offset associated with <em>file_descriptor</em>,
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unless O_APPEND is set for the file (see below). A successful <strong>
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write()</strong> increments the file offset by the number of bytes written. If
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the incremented file offset is greater than the previous length of the file,
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the length of the file is set to the new file offset.</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>write()</strong> sets the file offset to the end of
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the file before writing the output.</p>
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<p>If there is not enough room to write the requested number of bytes (for
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example, because there is not enough room on the disk), the <strong>
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write()</strong> function writes as many bytes as the remaining space can
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hold.</p>
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<p>If <strong>write()</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, the data is written
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to the file assuming it is in textual form. The maximum number of bytes on a
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single write that can be supported for text data is 2,147,483,408 (2GB - 240)
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bytes. The data is converted from the code page of the application, job, or
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system to the code page of the file as follows:</p>
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<ul>
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<li>When writing to a true stream file, any line-formatting characters (such as
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carriage return, tab, and end-of-file) are just converted from one code page to
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another.<br>
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<br>
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</li>
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<li>When writing to a record file that is being used as a stream file:<br>
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<br>
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<ul>
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<li>End-of-line characters are removed.</li>
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<li>Records are padded with blanks (for a source physical file member) or nulls
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(for a data physical file member).</li>
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<li>Tab characters are replaced by the appropriate number of blanks to the next
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tab position.</li>
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</ul>
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</li>
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</ul>
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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>The <strong>write()</strong> will attempt to convert all of the data in the
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user's buffer. Successfully converted data will be written. Unconverted data is
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usually assumed to be a partial character. Partial characters will be buffered
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internally and data from the next consecutive write will be appended to the
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buffered data. If incorrect data is provided on a consecutive write, the write
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may fail with the [ECONVERT] error.
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<p>If an <strong>lseek()</strong> is performed, the file is closed, or the
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current job is ended, the buffered data will be discarded. Discarded data will
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not be written to the file. See <a href="lseek.htm">lseek()</a>--Set File
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Read/Write Offset for more information.</p>
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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. For example, the user
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may supply a buffer to 100 bytes, but after an application has written the
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buffer to a new file, the file size may be 50, 200, or something else,
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depending on the CCSIDs involved.</li>
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</ul>
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<p>If O_TEXTDATA was not specified on the <strong>open()</strong>, the data is
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written to the file without conversion. The application is responsible for
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handling the data.</p>
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<p>When <em>file_descriptor</em> refers to a socket, the <strong>
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write()</strong> function writes to the socket identified by the socket
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descriptor.</p>
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<p><strong>Note:</strong> When the write 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 write is unsuccessful, the bits are undefined.</p>
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<p>Write requests to a pipe or FIFO are handled the same as a regular file,
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with the following exceptions:</p>
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<ul>
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<li>The S_ISUID and S_ISGID file mode bits will not be cleared.<br>
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<br>
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</li>
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<li>There is no file offset associated with a pipe or FIFO. Each write request
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will append to the end of the pipe or FIFO.<br>
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<br>
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</li>
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<li>Write requests of [PIPE_BUF] bytes or less will not be interleaved with
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data from other threads performing writes on the same pipe or FIFO. Writes of
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greater than [PIPE_BUF] bytes may have data interleaved on arbitrary boundaries
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with writes by other threads, whether or not the O_NONBLOCK flag of the file
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status flags is set.<br>
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<br>
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</li>
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<li>If the O_NONBLOCK flag was not specified and the pipe or FIFO is full, the
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write request will block the calling thread until the requested amount of data
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in <em>nbyte</em> is written.<br>
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<br>
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</li>
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<li>If the O_NONBLOCK flag was specified, then the following pertain to various
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write requests:<br>
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<br>
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<ul>
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<li>The <strong>write()</strong> function will not block the calling
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thread.<br>
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<br>
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</li>
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<li>A write request for [PIPE_BUF] or fewer bytes will have the following
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effect:
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<p>If there is sufficient space available in the pipe or FIFO, <strong>
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write()</strong> will transfer all the data and return the number of bytes
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requested. If there is not sufficient space in the pipe or FIFO, <strong>
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write()</strong> will transfer no data, return -1, and set <em>errno</em> to
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[EAGAIN].</p>
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</li>
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<li>A write request for more than [PIPE_BUF] bytes will cause one of the
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following:
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<ul>
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<li>When at least one byte can be written, <strong>write()</strong> will
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transfer what it can and return the number of bytes written.<br>
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<br>
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</li>
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<li>When no data can be written, <strong>write()</strong> will transfer no
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data, return -1, and set <em>errno</em> to [EAGAIN].</li>
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</ul>
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</li>
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</ul>
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</li>
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</ul>
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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 which the data is to be written.<br>
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<br>
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</dd>
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<dt><strong>buf</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>nbyte</strong></dt>
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<dd>(Input) The size in bytes of the data to be written.</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>write()</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>.<br>
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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>write()</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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<br>
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<h3>Error Conditions</h3>
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<p>If <strong>write()</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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<p>If writing to a socket, this error code indicates one of the following:</p>
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<ul>
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<li>The destination address specified is a broadcast address and the socket
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option <samp>SO_BROADCAST</samp> was not set (with a <em>
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setsockopt()</em>).</li>
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||
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<li>The process does not have the appropriate privileges to the destination
|
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address. This error code can only be returned on a socket with an address
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family of <samp>AF_INET</samp> and a type of <samp>SOCK_DGRAM</samp>.</li>
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||
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</ul>
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||
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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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<p>If <em>file_descriptor</em> refers to a pipe or FIFO that has its O_NONBLOCK
|
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flag set, this error occurs if the <strong>write()</strong> would have blocked
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||
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the calling thread.</p>
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||
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</td>
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||
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</tr>
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||
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<tr>
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||
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<td align="left" valign="top">
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||
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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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||
|
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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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||
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<td align="left" valign="top">
|
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|
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<em>[<a href="unix14.htm#EDAMAGE">EDAMAGE</a>]</em></td>
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|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EFAULT">EFAULT</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EFBIG">EFBIG</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>The size of the object would exceed the system allowed maximum size or the
|
||
|
|
process soft file size limit.
|
||
|
|
The file is a regular file, <em>nbyte</em> is greater than 0, and the
|
||
|
|
starting offset is greater than or equal to 2 GB minus 2 bytes.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EINTR">EINTR</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EINVAL">EINVAL</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>For example, the file system that the file resides in does not support large files, and
|
||
|
|
the starting offset exceeds 2GB minus 2 bytes.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EIO">EIO</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EJRNDAMAGE">EJRNDAMAGE</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EJRNENTTOOLONG">EJRNENTTOOLONG</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EJRNINACTIVE">EJRNINACTIVE</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EJRNRCVSPC">EJRNRCVSPC</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr><tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENEWJRN">ENEWJRN</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENEWJRNRCV">ENEWJRNRCV</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENOMEM">ENOMEM</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENOSPC">ENOSPC</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENOTAVAIL">ENOTAVAIL</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#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>
|
||
|
|
|
||
|
|
<p>When the descriptor refers to a socket, <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#ECONNREFUSED">ECONNREFUSED</a>]</em></td>
|
||
|
|
|
||
|
|
<td>
|
||
|
|
<p>This error code can only be returned on sockets that use a connectionless
|
||
|
|
transport service.</p>
|
||
|
|
</td></tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EDESTADDRREQ">EDESTADDRREQ</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>A destination address has not been associated with the socket pointed to by
|
||
|
|
the <em>fildes</em> parameter. This error code can only be returned on sockets
|
||
|
|
that use a connectionless transport service.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EHOSTDOWN">EHOSTDOWN</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>This error code can only be returned on sockets that use a connectionless
|
||
|
|
transport service.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EHOSTUNREACH">EHOSTUNREACH</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>This error code can only be returned on sockets that use a connectionless
|
||
|
|
transport service.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EINTR">EINTR</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EMSGSIZE">EMSGSIZE</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>The data to be sent could not be sent atomically because the size specified
|
||
|
|
by <em>nbyte</em> is too large.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENETDOWN">ENETDOWN</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>This error code can only be returned on sockets that use a connectionless
|
||
|
|
transport service.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENETUNREACH">ENETUNREACH</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>This error code can only be returned on sockets that use a connectionless
|
||
|
|
transport service.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENOBUFS">ENOBUFS</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#ENOTCONN">ENOTCONN</a>]</em></td>
|
||
|
|
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<p>This error code is returned only on sockets that use a connection-oriented
|
||
|
|
transport service.</p>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EPIPE">EPIPE</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>
|
||
|
|
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">
|
||
|
|
<em>[<a href="unix14.htm#EWOULDBLOCK">EWOULDBLOCK</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 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>
|
||
|
|
|
||
|
|
|
||
|
|
<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>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>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>write()</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>write()</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>write()</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. 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.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<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 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>Sockets Usage Notes<br>
|
||
|
|
<br>
|
||
|
|
<ol>
|
||
|
|
<li><strong>write()</strong> only works with sockets on which a <strong>
|
||
|
|
connect()</strong> has been issued, since it does not allow the caller to
|
||
|
|
specify a destination address.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>To broadcast on an <samp>AF_INET</samp> socket, the socket option <samp>
|
||
|
|
SO_BROADCAST</samp> must be set (with a <strong>setsockopt()</strong>).<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>When using a connection-oriented transport service, all errors except
|
||
|
|
<samp>[EUNATCH]</samp> and <samp>[EUNKNOWN]</samp> are mapped to <samp>
|
||
|
|
[EPIPE]</samp> on an output operation when either of the following occurs:<br>
|
||
|
|
<br>
|
||
|
|
<ul>
|
||
|
|
<li>A connection that is in progress is unsuccessful.</li>
|
||
|
|
|
||
|
|
<li>An established connection is broken.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>To get the actual error, use <strong>getsockopt()</strong> with the <samp>
|
||
|
|
SO_ERROR</samp> option, or perform an input operation (for example, <strong>
|
||
|
|
read()</strong>).</p>
|
||
|
|
</li>
|
||
|
|
</ol>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>For the file systems that do not support large files, <strong>
|
||
|
|
write()</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>write()</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 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.</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="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="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="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;
|
||
|
|
char fn[]="write.file";
|
||
|
|
|
||
|
|
if ((mega_string = (char*) malloc(mega_string_len)) == 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 = write(file_descriptor, mega_string, mega_string_len)) == -1)
|
||
|
|
perror("write() error");
|
||
|
|
else printf("write() wrote %d bytes\n", ret);
|
||
|
|
if (close(file_descriptor)!= 0)
|
||
|
|
perror("close() error");
|
||
|
|
if (unlink(fn)!= 0)
|
||
|
|
perror("unlink() error");
|
||
|
|
}
|
||
|
|
free(mega_string);
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<p><strong>Output:</strong></p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
write() wrote 1000000 bytes
|
||
|
|
</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>
|
||
|
|
|