blocks|key|5061704|text|freopen还可以与cin和cout一起使用。不需要搜索新的东西。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5061705|freopen("input.txt",+"r",+stdin);+//+redirects+standard+input
freopen("output.txt",+"w",+stdout);+//+redirects+standard+output

int+x;
cin+>>+x;+//+reads+from+input.txt
cout+<<+x+<<+endl;+//+writes+to+output.txt|code-block|syntax|javascript|5061706|编辑:来自C%2B%2B标准27.3.1的：|BOLD|5061707|5061708|对象cin控制来自与<cstdio>中声明的对象stdin相关联的流缓冲器的输入。|blockquote|5061709|5061710|5061711|所以根据标准，如果我们重定向stdin，它也会重定向cin。对于cout，反之亦然。|5061712|entityMap^0|0|7|B|3|F|4|0|0|0|H|0|0|A|8|0|0|0|E|5|Q|3|W|4|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@$9|16|A|17|B|M]]|D|@]|E|$]]|$1|N|3|-4|5|6|7|18|8|@]|D|@]|E|$]]|$1|O|3|P|5|Q|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]|$1|T|3|U|5|6|7|1E|8|@$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]]|D|@]|E|$]]|$1|V|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|W|$]]

<code>freopen</code> also works with <code>cin</code> and <code>cout</code>. No need to search for something new.

<pre><code>freopen("input.txt", "r", stdin); // redirects standard input
freopen("output.txt", "w", stdout); // redirects standard output

int x;
cin &gt;&gt; x; // reads from input.txt
cout &lt;&lt; x &lt;&lt; endl; // writes to output.txt
</code></pre>

Edit: From C++ standard 27.3.1:

<blockquote>
 The object cin controls input from a stream buffer associated with the object stdin, declared in <code>&lt;cstdio&gt;</code>.
</blockquote>

So according to the standard, if we redirect <code>stdin</code> it will also redirect <code>cin</code>. Vice versa for <code>cout</code>.

blocks|key|5061741|text|This新闻组帖子探索您的选择。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|5061742|5061743|这是系统相关的，海报没有指明系统，但cin.clear()应该可以工作。我已经在装有AT&T版本iostreams的UNIX系统上测试了附加的程序。|blockquote|5061744|5061745|5061746|#include+<iostream.h>
int+main()
{
++++for(;;)+{
++++++++if+(+cin.eof()+)+{
++++++++++++cout+<<+"EOF"+<<+endl;
++++++++++++cin.clear();
++++++++}
++++++++char+c+;
++++++++if+(+cin.get(c)+)+cout.put(c)+;
++++}
}+|code-block|syntax|javascript|5061747|5061748|是的，它在cfront和TC%2B%2B中工作得很好。在最先出现问题的g%2B%2B中，需要执行额外的操作：|5061749|5061750|5061751|++cin.clear();
++rewind+(+_iob+);+//+Seems+quite+out+of+place,+doesn't+it?
+++++++++++++++++++//+cfront+also+accepts+but+doesn't
+++++++++++++++++++//+require+this+rewind.+|5061752|虽然我注意到这是在1991年，但它应该仍然有效。记住使用现在标准的iostream标头，而不是iostream.h。|style|CODE|5061753|(顺便说一句，我发现这篇帖子的谷歌搜索词是"reopen+cin+c%2B%2B"，第二个结果。)|5061754|让我们知道你的进展如何。你也可以直接使用freopen。|5061755|entityMap|0|LINK|mutability|MUTABLE|url|http://groups.google.com/group/comp.lang.c%2B%2B/msg/80ca417acb84858f^0|0|4|0|0|0|0|0|0|0|0|0|0|0|0|X|8|1B|A|0|0|K|7|0^^$0|@$1|2|3|4|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|D|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|1G|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|1H|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|1I|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|1J|8|@]|9|@]|C|$M|N]]|$1|O|3|-4|5|6|7|1K|8|@]|9|@]|C|$]]|$1|P|3|Q|5|G|7|1L|8|@]|9|@]|C|$]]|$1|R|3|-4|5|6|7|1M|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1N|8|@]|9|@]|C|$]]|$1|T|3|U|5|L|7|1O|8|@]|9|@]|C|$M|N]]|$1|V|3|W|5|6|7|1P|8|@$A|1Q|B|1R|X|Y]|$A|1S|B|1T|X|Y]]|9|@]|C|$]]|$1|Z|3|10|5|6|7|1U|8|@]|9|@]|C|$]]|$1|11|3|12|5|6|7|1V|8|@$A|1W|B|1X|X|Y]]|9|@]|C|$]]|$1|13|3|-4|5|6|7|1Y|8|@]|9|@]|C|$]]]|14|$15|$5|16|17|18|C|$19|1A]]]]

<a href="http://groups.google.com/group/comp.lang.c++/msg/80ca417acb84858f" rel="nofollow">This</a> newsgroup posting explores your options.

<blockquote>
 This is system dependent and the poster didn't indicate the
 system, but cin.clear() should work. I have tested the attached
 program on a UNIX system with AT&amp;T version's of iostreams. 
</blockquote>

<pre><code>#include &lt;iostream.h&gt;
int main()
{
 for(;;) {
 if ( cin.eof() ) {
 cout &lt;&lt; "EOF" &lt;&lt; endl;
 cin.clear();
 }
 char c ;
 if ( cin.get(c) ) cout.put(c) ;
 }
} 
</code></pre>

<blockquote>
 Yes, that works okay in cfront and TC++.
 In g++ where the problem first arose an additional action is required:
</blockquote>

<pre><code> cin.clear();
 rewind ( _iob ); // Seems quite out of place, doesn't it?
 // cfront also accepts but doesn't
 // require this rewind. 
</code></pre>

Though I note that this was in 1991, it should still work. Remember to use the now-standard <code>iostream</code> header, not <code>iostream.h</code>.

(BTW I found that post with the Google search terms "reopen cin c++", second result.)

Let us know how you get on. You could also just use <code>freopen</code>.

blocks|key|5061757|text|#include+<iostream>
#include+<fstream>

int+main()+{

++//+Read+one+line+from+stdin
++std::string+line;
++std::getline(std::cin,+line);
++std::cout+<<+line+<<+"\n";

++//+Read+a+line+from+/etc/issue
++std::ifstream+issue("/etc/issue");
++std::streambuf*+issue_buf+=+issue.rdbuf();
++std::streambuf*+cin_buf+=+std::cin.rdbuf(issue_buf);
++std::getline(std::cin,+line);
++std::cout+<<+line+<<+"\n";

++//+Restore+sanity+and+read+a+line+from+stdin
++std::cin.rdbuf(cin_buf);
++std::getline(std::cin,+line);
++std::cout+<<+line+<<+"\n";
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|5061758|http://www.cplusplus.com/reference/iostream/ios/rdbuf/|unstyled|offset|length|5061759|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1I|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|Q|8|@]|9|@$G|R|H|S|1|T]]|A|$]]|$1|I|3|-4|5|F|7|U|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|E]]]]

<pre><code>#include &lt;iostream&gt;
#include &lt;fstream&gt;

int main() {

 // Read one line from stdin
 std::string line;
 std::getline(std::cin, line);
 std::cout &lt;&lt; line &lt;&lt; "\n";

 // Read a line from /etc/issue
 std::ifstream issue("/etc/issue");
 std::streambuf* issue_buf = issue.rdbuf();
 std::streambuf* cin_buf = std::cin.rdbuf(issue_buf);
 std::getline(std::cin, line);
 std::cout &lt;&lt; line &lt;&lt; "\n";

 // Restore sanity and read a line from stdin
 std::cin.rdbuf(cin_buf);
 std::getline(std::cin, line);
 std::cout &lt;&lt; line &lt;&lt; "\n";
}
</code></pre>

<a href="http://www.cplusplus.com/reference/iostream/ios/rdbuf/" rel="noreferrer">http://www.cplusplus.com/reference/iostream/ios/rdbuf/</a>

When programming with c-style i/o I sometimes use freopen() to reopen stdin for testing purposes so that I don't have to retype the input over and over. I was wondering if there is an equivalent for c++ i/o streams. Also, I know that I can use pipes to redirect it on the command line/terminal/whateveritis but I was wondering if there was a way to do it inside my code (because as you can see, I'm not very knowledgeable about the cl/t/w).

freopen() equivalent for c++ streams

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

当使用c风格的i/o编程时，我有时会使用freopen()重新打开stdin进行测试，这样我就不必一次又一次地重新输入输入。我想知道是否有用于c++ i/o流的等价物。此外，我知道我可以使用管道在命令行/终端/其他地方重定向它，但我想知道是否有一种方法可以在我的代码中做到这一点(因为正如你所看到的，我对cl/t/w不是...

问c++ streams的freopen()等效项
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问c++ streams的freopen()等效项EN