259 lines
19 KiB
HTML
259 lines
19 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::basic_istream<CharT,Traits>::get</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_istream_get skin-cppreference2 action-view cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_istream<CharT,Traits>::</span>get</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-io.html">io</a>‎ | <a href="cpp-io-basic_istream.html">basic istream</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp">int_type get<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(1)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp">basic_istream<span class="sy3">&</span> get<span class="br0">(</span> char_type<span class="sy3">&</span> ch <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(2)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp">basic_istream<span class="sy3">&</span> get<span class="br0">(</span> char_type<span class="sy2">*</span> s, <a href="cpp-io-streamsize.html"><span class="kw1804">std::<span class="me2">streamsize</span></span></a> count <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(3)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp">basic_istream<span class="sy3">&</span> get<span class="br0">(</span> char_type<span class="sy2">*</span> s, <a href="cpp-io-streamsize.html"><span class="kw1804">std::<span class="me2">streamsize</span></span></a> count, char_type delim <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(4)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp">basic_istream<span class="sy3">&</span> get<span class="br0">(</span> basic_streambuf<span class="sy3">&</span> strbuf <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(5)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp">basic_istream<span class="sy3">&</span> get<span class="br0">(</span> basic_streambuf<span class="sy3">&</span> strbuf, char_type delim <span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(6)</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>从流释出字符或多个字符。</p>
|
|
<p>所有版本都表现为<a href="cpp-named_req-UnformattedInputFunction.html"><span style="font-style:italic">无格式输入函数</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(UnformattedInputFunction)</span></a> 。构造并检查 sentry 对象后,这些函数进行下列内容:</p>
|
|
<div class="t-li1"><span class="t-li">1)</span> 读取一个字符,若可用则返回它。否则,返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">eof</span><span class="br0">(</span><span class="br0">)</span></span></span> 并设置 <span class="t-lc"><a href="cpp-io-ios_base-iostate.html">failbit</a></span> 和 <span class="t-lc"><a href="cpp-io-ios_base-iostate.html">eofbit</a></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 读取一个字符,而若可用则存储于 <code>ch</code> 。否则,保留 <code>ch</code> 不修改并设置 <span class="t-lc"><a href="cpp-io-ios_base-iostate.html">failbit</a></span> 和 <span class="t-lc"><a href="cpp-io-ios_base-iostate.html">eofbit</a></span> 。注意此函数不在类型 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">signed</span> <span class="kw4">char</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">char</span></span></span> 重载,不同于有格式字符输入 operator>> 。</div>
|
|
<div class="t-li1"><span class="t-li">3)</span> 同 <span class="t-c"><span class="mw-geshi cpp source-cpp">get<span class="br0">(</span>s, count, widen<span class="br0">(</span><span class="st0">'<span class="es1">\n</span>'</span><span class="br0">)</span><span class="br0">)</span></span></span> ,即读取至多 <span class="t-c"><span class="mw-geshi cpp source-cpp">count<span class="sy2">-</span><span class="nu0">1</span></span></span> 个字符并存储它们到 <code>s</code> 所指向的字符串中,直至找到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">'<span class="es1">\n</span>'</span></span></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">4)</span> 读取字符并存储它们到首元素为 <code>s</code> 所指向的字符数组的相继位置。释出并存储字符,直至出现任何下列条件:</div>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>已存储 <span class="t-c"><span class="mw-geshi cpp source-cpp">count <span class="sy2">-</span> <span class="nu0">1</span></span></span> 个字符</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>输入序列中出现文件尾条件(调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">setstate<span class="br0">(</span>eofbit<span class="br0">)</span></span></span> )</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>下个可用输入字符 <code>c</code> 等于 <code>delim</code> ,以 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">eq</span><span class="br0">(</span>c, delim<span class="br0">)</span></span></span> 确定。不释出此字符(不同于 <span class="t-lc"><a href="cpp-io-basic_istream-getline.html">basic_istream::getline()</a></span> )。</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<div class="t-li1"><span class="t-li"></span> 若未释出字符,则调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">setstate<span class="br0">(</span>failbit<span class="br0">)</span></span></span> 。任何情况下,若 <code>count>0</code> ,则存储空字符( <span class="t-c"><span class="mw-geshi cpp source-cpp">CharT<span class="br0">(</span><span class="br0">)</span></span></span> )于数组的下个相继位置。</div>
|
|
<div class="t-li1"><span class="t-li">5)</span> 同 <span class="t-c"><span class="mw-geshi cpp source-cpp">get<span class="br0">(</span>strbuf, widen<span class="br0">(</span><span class="st0">'<span class="es1">\n</span>'</span><span class="br0">)</span><span class="br0">)</span></span></span> ,即读取可用字符并插入它们到给定的 <a href="cpp-io-basic_streambuf.html"><tt>basic_streambuf</tt></a> 对象,直至找到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">'<span class="es1">\n</span>'</span></span></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">6)</span> 读取字符并插入它们到给定的 <a href="cpp-io-basic_streambuf.html"><tt>basic_streambuf</tt></a> 对象所控制的输出序列。释出并插入字符到 <code>strbuf</code> 中,直至出现任何下列条件:</div>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>输入序列中出现文件尾条件</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>插入输出序列失败(该情况下不释出无法插入的字符)</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>下个可用输入字符 <code>c</code> 等于 <code>delim</code> ,以 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">eq</span><span class="br0">(</span>c, delim<span class="br0">)</span></span></span> 确定。不释出此字符。</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<dl>
|
|
<dd>
|
|
<dl>
|
|
<dd>
|
|
<ul>
|
|
<li>出现异常(该情况下捕获而不重抛异常)。</li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
</dd>
|
|
</dl>
|
|
<div class="t-li1"><span class="t-li"></span> 若未释出字符,则调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">setstate<span class="br0">(</span>failbit<span class="br0">)</span></span></span> 。</div>
|
|
<p>所有版本都设置 <span class="t-lc"><a href="cpp-io-basic_istream-gcount.html">gcount()</a></span> 的值为释出的字符数。</p>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>ch</td>
|
|
<td>-</td>
|
|
<td>到要写入结果到的字符的引用</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>s</td>
|
|
<td>-</td>
|
|
<td>指向要存储结果到的字符串的指针</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>count</td>
|
|
<td>-</td>
|
|
<td><code>s</code> 所指向的字符串的大小</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>delim</td>
|
|
<td>-</td>
|
|
<td>用以停止释出的分隔字符。不释出且不存储它。</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>strbuf</td>
|
|
<td>-</td>
|
|
<td>要读取内容到的流缓冲</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<div class="t-li1"><span class="t-li">1)</span> 释出的字符或 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">eof</span><span class="br0">(</span><span class="br0">)</span></span></span></div>
|
|
<div class="t-li1"><span class="t-li">2-6)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span></div>
|
|
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
|
|
<div class="t-template-editlink" style=""></div>
|
|
若出现错误(错误状态标志不是 <span class="t-lc"><a href="cpp-io-ios_base-iostate.html">goodbit</a></span> )并且设置了 <span class="t-lc"><a href="cpp-io-basic_ios-exceptions.html">exceptions()</a></span> 为对该状态抛出则为 <span class="t-lc"><a href="cpp-io-ios_base-failure.html">failure</a></span> 。
|
|
<p>若内部操作抛出异常,则捕获它并设置 <span class="t-lc"><a href="cpp-io-ios_base-iostate.html">badbit</a></span> 。若对 <code>badbit</code> 设置了 <span class="t-lc"><a href="cpp-io-basic_ios-exceptions.html">exceptions()</a></span> ,则重抛该异常。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <sstream></span>
|
|
<span class="co2">#include <iostream></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-io-basic_istringstream.html"><span class="kw1735">std::<span class="me2">istringstream</span></span></a> s1<span class="br0">(</span><span class="st0">"Hello, world."</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw4">char</span> c1 <span class="sy1">=</span> s1.<span class="me1">get</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 读取'H'</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"after reading "</span> <span class="sy1"><<</span> c1 <span class="sy1"><<</span> <span class="st0">", gcount() == "</span> <span class="sy1"><<</span> s1.<span class="me1">gcount</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="kw4">char</span> c2<span class="sy4">;</span>
|
|
s1.<span class="me1">get</span><span class="br0">(</span>c2<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 读取 'e'</span>
|
|
<span class="kw4">char</span> str<span class="br0">[</span><span class="nu0">5</span><span class="br0">]</span><span class="sy4">;</span>
|
|
s1.<span class="me1">get</span><span class="br0">(</span>str, <span class="nu0">5</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 读取 "llo,"</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"after reading "</span> <span class="sy1"><<</span> str <span class="sy1"><<</span> <span class="st0">", gcount() == "</span> <span class="sy1"><<</span> s1.<span class="me1">gcount</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> c1 <span class="sy1"><<</span> c2 <span class="sy1"><<</span> str<span class="sy4">;</span>
|
|
s1.<span class="me1">get</span><span class="br0">(</span><span class="sy2">*</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 读取剩余,不包括 '\n'</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>After the last get(), gcount() == "</span> <span class="sy1"><<</span> s1.<span class="me1">gcount</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出:</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">after reading H, gcount() == 1
|
|
after reading llo,, gcount() == 4
|
|
Hello, world.
|
|
After the last get(), gcount() == 7</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-io-basic_istream-read.html"><span class="t-lines"><span>read</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>读并取走一块字符<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-io-basic_istream-operator_gtgt.html"><span class="t-lines"><span>operator>></span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>提取带格式数据<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-io-basic_istream-operator_gtgt2.html"><span class="t-lines"><span>operator>><span class="t-dsc-small">(std::basic_istream)</span></span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>提取字符和字符数组<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|