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<!DOCTYPE html>
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>ftell</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_io_ftell skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading">ftell</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="c.html">c</a>&lrm; | <a href="c-io.html">io</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code>&lt;stdio.h&gt;</code></div>
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<div><span class="mw-geshi c source-c"><span class="kw4">long</span> ftell<span class="br0">(</span> <a href="c-io.html"><span class="kw883">FILE</span></a> <span class="sy2">*</span>stream <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>&#36820;&#22238;&#27969; <code>stream</code> &#30340;&#25991;&#20214;&#20301;&#32622;&#25351;&#31034;&#22120;&#12290;</p>
<p>&#33509;&#27969;&#20197;&#20108;&#36827;&#21046;&#27169;&#24335;&#25171;&#24320;&#65292;&#21017;&#30001;&#27492;&#20989;&#25968;&#33719;&#24471;&#30340;&#20540;&#26159;&#20174;&#25991;&#20214;&#24320;&#22987;&#30340;&#23383;&#33410;&#25968;&#12290;</p>
<p>&#33509;&#27969;&#20197;&#25991;&#26412;&#27169;&#24335;&#25171;&#24320;&#65292;&#21017;&#30001;&#27492;&#20989;&#25968;&#36820;&#22238;&#30340;&#20540;&#26410;&#25351;&#23450;&#65292;&#19988;&#20165;&#33509;&#20316;&#20026; <span class="t-lc"><a href="c-io-fseek.html">fseek()</a></span> &#30340;&#36755;&#20837;&#25165;&#26377;&#24847;&#20041;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
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<td>stream</td>
<td>-</td>
<td>&#35201;&#26816;&#39564;&#30340;&#25991;&#20214;&#27969;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#25104;&#21151;&#26102;&#20026;&#25991;&#20214;&#20301;&#32622;&#25351;&#31034;&#22120;&#65292;&#33509;&#22833;&#36133;&#21457;&#29983;&#21017;&#20026; <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">-</span><span class="nu0">1L</span></span></span> &#12290;</p>
<p>&#22833;&#36133;&#26102;&#65292;&#35774; <span class="t-c"><span class="mw-geshi c source-c"><span class="kw2">errno</span></span></span> &#23545;&#35937;&#20026;&#23454;&#29616;&#23450;&#20041;&#30340;&#27491;&#20540;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<p>ftell&#24102;&#38169;&#35823;&#26816;&#26597;</p>
<div class="t-example-live-link"></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="c source-c">
<pre class="de1"><span class="co2">#include &lt;stdio.h&gt;</span>
<span class="co2">#include &lt;stdlib.h&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="coMULTI">/* &#20934;&#22791;&#28014;&#28857;&#20540;&#30340;&#25968;&#32452;&#12290; */</span>
<span class="co2">#define SIZE 5</span>
<span class="kw4">double</span> A<span class="br0">[</span>SIZE<span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">1</span>.,<span class="nu0">2</span>.,<span class="nu0">3</span>.,<span class="nu0">4</span>.,<span class="nu0">5</span>.<span class="br0">}</span><span class="sy4">;</span>
<span class="coMULTI">/* &#20889;&#25968;&#32452;&#21040;&#25991;&#20214;&#12290; */</span>
<a href="c-io.html"><span class="kw883">FILE</span></a> <span class="sy2">*</span> fp <span class="sy1">=</span> <a href="c-io-fopen.html"><span class="kw819">fopen</span></a><span class="br0">(</span><span class="st0">&quot;test.bin&quot;</span>, <span class="st0">&quot;wb&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-fwrite.html"><span class="kw826">fwrite</span></a><span class="br0">(</span>A,<span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">double</span><span class="br0">)</span>,SIZE,fp<span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-fclose.html"><span class="kw822">fclose</span></a> <span class="br0">(</span>fp<span class="br0">)</span><span class="sy4">;</span>
<span class="coMULTI">/* &#35835;&#21462;&#28014;&#28857;&#20540;&#21040;&#25968;&#32452; B&#12290; */</span>
<span class="kw4">double</span> B<span class="br0">[</span>SIZE<span class="br0">]</span><span class="sy4">;</span>
fp <span class="sy1">=</span> <a href="c-io-fopen.html"><span class="kw819">fopen</span></a><span class="br0">(</span><span class="st0">&quot;test.bin&quot;</span>,<span class="st0">&quot;rb&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">long</span> <span class="kw4">int</span> pos <span class="sy1">=</span> ftell<span class="br0">(</span>fp<span class="br0">)</span><span class="sy4">;</span> <span class="coMULTI">/* &#20301;&#32622;&#25351;&#31034;&#22120;&#22312;&#25991;&#20214;&#36215;&#22987; */</span>
<span class="kw1">if</span> <span class="br0">(</span>pos <span class="sy1">==</span> <span class="sy2">-</span><span class="nu0">1L</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="c-io-perror.html"><span class="kw878">perror</span></a><span class="br0">(</span><span class="st0">&quot;ftell()&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-fprintf.html"><span class="kw852">fprintf</span></a><span class="br0">(</span><a href="c-io.html"><span class="kw887">stderr</span></a>,<span class="st0">&quot;ftell() failed in file %s at line # %d<span class="es1">\n</span>&quot;</span>, __FILE__,__LINE__<span class="sy2">-</span><span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-program-exit.html"><span class="kw488">exit</span></a><span class="br0">(</span><a href="c-program-EXIT_status.html"><span class="kw494">EXIT_FAILURE</span></a><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">&quot;%ld<span class="es1">\n</span>&quot;</span>, pos<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">int</span> ret_code <span class="sy1">=</span> <a href="c-io-fread.html"><span class="kw825">fread</span></a><span class="br0">(</span>B,<span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">double</span><span class="br0">)</span>,<span class="nu0">1</span>,fp<span class="br0">)</span><span class="sy4">;</span> <span class="coMULTI">/* &#35835;&#21462;&#19968;&#20010;&#28014;&#28857;&#20540; */</span>
pos <span class="sy1">=</span> ftell<span class="br0">(</span>fp<span class="br0">)</span><span class="sy4">;</span> <span class="coMULTI">/* &#35835;&#21462;&#19968;&#20010;&#28014;&#28857;&#20540;&#21518;&#30340;&#20301;&#32622;&#25351;&#31034;&#22120; */</span>
<span class="kw1">if</span> <span class="br0">(</span>pos <span class="sy1">==</span> <span class="sy2">-</span><span class="nu0">1L</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="c-io-perror.html"><span class="kw878">perror</span></a><span class="br0">(</span><span class="st0">&quot;ftell()&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-fprintf.html"><span class="kw852">fprintf</span></a><span class="br0">(</span><a href="c-io.html"><span class="kw887">stderr</span></a>,<span class="st0">&quot;ftell() failed in file %s at line # %d<span class="es1">\n</span>&quot;</span>, __FILE__,__LINE__<span class="sy2">-</span><span class="nu0">4</span><span class="br0">)</span><span class="sy4">;</span>
<a href="c-program-exit.html"><span class="kw488">exit</span></a><span class="br0">(</span><a href="c-program-EXIT_status.html"><span class="kw494">EXIT_FAILURE</span></a><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">&quot;%ld<span class="es1">\n</span>&quot;</span>, pos<span class="br0">)</span><span class="sy4">;</span>
<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">&quot;%.1f<span class="es1">\n</span>&quot;</span>, B<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span> <span class="coMULTI">/* &#25171;&#21360;&#28014;&#28857;&#20540; */</span>
<span class="kw1">return</span> <a href="c-program-EXIT_status.html"><span class="kw493">EXIT_SUCCESS</span></a><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">0
8
1.0</pre></div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">&#24341;&#29992;</span></h3>
<div class="t-ref-std-11">
<ul>
<li>C11 &#26631;&#20934;&#65288;ISO/IEC 9899:2011&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>7.21.9.4 The ftell function (p: 337-338)</li>
</ul>
</dd>
</dl>
<div class="t-ref-std-c99">
<ul>
<li>C99 &#26631;&#20934;&#65288;ISO/IEC 9899:1999&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>7.19.9.4 The ftell function (p: 303-304)</li>
</ul>
</dd>
</dl>
<div class="t-ref-std-c89">
<ul>
<li>C89/C90 &#26631;&#20934;&#65288;ISO/IEC 9899:1990&#65289;&#65306;</li>
</ul>
<dl>
<dd>
<ul>
<li>4.9.9.4 The ftell function</li>
</ul>
</dd>
</dl>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div class="t-dsc-member-div">
<div><a href="c-io-fgetpos.html"><span class="t-lines"><span>fgetpos</span></span></a></div>
</div>
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<td>&#33719;&#21462;&#25991;&#20214;&#20301;&#32622;&#25351;&#31034;&#22120;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="c-io-fseek.html"><span class="t-lines"><span>fseek</span></span></a></div>
</div>
</td>
<td>&#23558;&#25991;&#20214;&#20301;&#32622;&#25351;&#31034;&#31526;&#31227;&#21160;&#21040;&#25991;&#20214;&#20013;&#30340;&#25351;&#23450;&#20301;&#32622;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
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<div class="t-dsc-member-div">
<div><a href="c-io-fsetpos.html"><span class="t-lines"><span>fsetpos</span></span></a></div>
</div>
</td>
<td>&#23558;&#25991;&#20214;&#20301;&#32622;&#25351;&#31034;&#22120;&#31227;&#21160;&#21040;&#25991;&#20214;&#20013;&#30340;&#25351;&#23450;&#20301;&#32622;<br />
<span class="t-mark">(&#20989;&#25968;)</span></td>
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