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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>fwrite</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="fwrite"></a> <a name="tag_03_205"></a><!-- fwrite --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_205_01"></a>NAME</h4><blockquote>fwrite - binary output</blockquote><h4><a name="tag_03_205_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/stdio.h.html">stdio.h</a>><br><br> size_t fwrite(const void *restrict</tt> <i>ptr</i><tt>, size_t</tt> <i>size</i><tt>, size_t</tt> <i>nitems</i><tt>,<br> FILE *restrict</tt> <i>stream</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_205_03"></a>DESCRIPTION</h4><blockquote><div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers tothe ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div><p>The <i>fwrite</i>() function shall write, from the array pointed to by <i>ptr</i>, up to <i>nitems</i> elements whose size isspecified by <i>size</i>, to the stream pointed to by <i>stream</i>. For each object, <i>size</i> calls shall be made to the <ahref="../functions/fputc.html"><i>fputc</i>()</a> function, taking the values (in order) from an array of <b>unsigned char</b>exactly overlaying the object. The file-position indicator for the stream (if defined) shall be advanced by the number of bytessuccessfully written. If an error occurs, the resulting value of the file-position indicator for the stream is unspecified.</p><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> The<i>st_ctime</i> and <i>st_mtime</i> fields of the file shall be marked for update between the successful execution of<i>fwrite</i>() and the next successful completion of a call to <a href="../functions/fflush.html"><i>fflush</i>()</a> or <a href="../functions/fclose.html"><i>fclose</i>()</a> on the same stream, or a call to <a href="../functions/exit.html"><i>exit</i>()</a>or <a href="../functions/abort.html"><i>abort</i>()</a>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_205_04"></a>RETURN VALUE</h4><blockquote><p>The <i>fwrite</i>() function shall return the number of elements successfully written, which may be less than <i>nitems</i> if awrite error is encountered. If <i>size</i> or <i>nitems</i> is 0, <i>fwrite</i>() shall return 0 and the state of the streamremains unchanged. Otherwise, if a write error occurs, the error indicator for the stream shall be set, <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and<i>errno</i> shall be set to indicate the error. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_205_05"></a>ERRORS</h4><blockquote><p>Refer to <a href="fputc.html"><i>fputc</i>()</a>.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_205_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_205_07"></a>APPLICATION USAGE</h4><blockquote><p>Because of possible differences in element length and byte ordering, files written using <i>fwrite</i>() areapplication-dependent, and possibly cannot be read using <a href="../functions/fread.html"><i>fread</i>()</a> by a differentapplication or by the same application on a different processor.</p></blockquote><h4><a name="tag_03_205_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_205_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_205_10"></a>SEE ALSO</h4><blockquote><p><a href="ferror.html"><i>ferror</i>()</a>, <a href="fopen.html"><i>fopen</i>()</a>, <a href="printf.html"><i>printf</i>()</a>, <a href="putc.html"><i>putc</i>()</a>, <a href="puts.html"><i>puts</i>()</a>, <a href="write.html"><i>write</i>()</a>, theBase Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a></p></blockquote><h4><a name="tag_03_205_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_205_12"></a>Issue 6</h4><blockquote><p>Extensions beyond the ISO C standard are marked.</p><p>The following changes are made for alignment with the ISO/IEC 9899:1999 standard:</p><ul><li><p>The <i>fwrite</i>() prototype is updated.</p></li><li><p>The DESCRIPTION is updated to clarify how the data is written out using <a href="../functions/fputc.html"><i>fputc</i>()</a>.</p></li></ul></blockquote><div class="box"><em>End of informative text.</em></div><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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