blocks|key|1478203|text|要使用代码1，您必须像这样调用您的程序：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1478204|App.exe+<+inputfile+>+outputfile|code-block|syntax|javascript|1478205|您还可以使用：|1478206|App.exe+<+inputfile+>>+outputfile|1478207|在这种情况下，输出不会用命令的每次运行来重写，但是输出将被附加到已经存在的文件中。|1478208|有关在Windows中重定向输入和输出的更多信息，您可以找到这里。|offset|length|1478209|请注意，<、>和>>符号将逐字输入--它们不只是用于本解释中的表示目的。因此，例如：|style|CODE|1478210|App.exe+<+file1+>>+file2|1478211|entityMap|0|LINK|mutability|MUTABLE|url|http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/redirection.mspx?mfr=true^0|0|0|0|0|0|U|2|0|0|4|1|6|1|8|2|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|16|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@$O|1A|P|1B|1|1C]]|A|$]]|$1|Q|3|R|5|6|7|1D|8|@$O|1E|P|1F|S|T]|$O|1G|P|1H|S|T]|$O|1I|P|1J|S|T]]|9|@]|A|$]]|$1|U|3|V|5|D|7|1K|8|@]|9|@]|A|$E|F]]|$1|W|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]]]

To use your code [1] you have to call your program like this:

<pre><code>App.exe &lt; inputfile &gt; outputfile
</code></pre>

You can also use:

<pre><code>App.exe &lt; inputfile &gt;&gt; outputfile
</code></pre>

In this case the output wouldn't be rewritten with every run of the command, but output will be appended to already existing file.

More information about redirecting input and output in Windows you can find <a href="http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/redirection.mspx?mfr=true" rel="noreferrer">here</a>.

<hr>

Note that the <code>&lt;</code>, <code>&gt;</code> and <code>&gt;&gt;</code> symbols are to be entered verbatim &mdash; they are not just for presentation purposes in this explanation. So, for example:

<pre><code>App.exe &lt; file1 &gt;&gt; file2
</code></pre>

blocks|key|401987|text|除了原来的重定向，>/+>>和<|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|401988|您也可以重定向std::cin和std::cout。|401989|如下所示：|401990|int+main()
{
++++//+Save+original+std::cin,+std::cout
++++std::streambuf+*coutbuf+=+std::cout.rdbuf();
++++std::streambuf+*cinbuf+=+std::cin.rdbuf();+

++++std::ofstream+out("outfile.txt");
++++std::ifstream+in("infile.txt");

++++//Read+from+infile.txt+using+std::cin
++++std::cin.rdbuf(in.rdbuf());

++++//Write+to+outfile.txt+through+std::cout+
++++std::cout.rdbuf(out.rdbuf());+++

++++std::string+test;
++++std::cin+>>+test;+++++++++++//from+infile.txt
++++std::cout+<<+test+<<+"++";+//to+outfile.txt

++++//Restore+back.
++++std::cin.rdbuf(cinbuf);+++
++++std::cout.rdbuf(coutbuf);+

}|code-block|syntax|javascript|401991|entityMap^0|9|1|C|2|F|1|0|7|8|G|9|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|12|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|13|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|P|$]]

In addition to original redirection <code>&gt;</code>/ <code>&gt;&gt;</code> and <code>&lt;</code>

You can redirect <code>std::cin</code> and <code>std::cout</code> too.

Like following:

<pre><code>int main()
{
 // Save original std::cin, std::cout
 std::streambuf *coutbuf = std::cout.rdbuf();
 std::streambuf *cinbuf = std::cin.rdbuf(); 

 std::ofstream out("outfile.txt");
 std::ifstream in("infile.txt");

 //Read from infile.txt using std::cin
 std::cin.rdbuf(in.rdbuf());

 //Write to outfile.txt through std::cout 
 std::cout.rdbuf(out.rdbuf()); 

 std::string test;
 std::cin &gt;&gt; test; //from infile.txt
 std::cout &lt;&lt; test &lt;&lt; " "; //to outfile.txt

 //Restore back.
 std::cin.rdbuf(cinbuf); 
 std::cout.rdbuf(coutbuf); 

}
</code></pre>

blocks|key|402048|text|我只是在解释有关的命令行参数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|402049|您可以将文件名作为命令行输入提供给可执行文件，但随后需要在代码中打开它们。|402050|喜欢|402051|您提供了两个命令行参数，即inputfile+&+outputfile。|402052|App.exe+inputfile+outputfile|offset|length|style|CODE|402053|现在在你的代码中|402054|#include<iostream>
#include<fstream>
#include<string>

int+main(int+argc,+char+*+argv[])
{
+++//argv[0]+:=+A.exe
+++//argv[1]+:=+inputFile
+++//argv[2]+:=+outputFile

+++std::ifstream+vInFile(argv[1],std::ios::in);+
+++//+notice+I+have+given+first+command+line+argument+as+file+name

+++std::ofstream+vOutFile(argv[2],std::ios::out+%7C+std::ios::app);
+++//+notice+I+have+given+second+command+line+argument+as+file+name

+++if+(vInFile.is_open())
+++{
+++++std::string+line;

+++++getline+(vInFile,line);+//Fixing+it+as+per+the+comment+made+by+MSalters

+++++while+(+vInFile.good()+)
+++++{
+++++++++vOutFile+<<+line+<<+std::endl;
+++++++++getline+(vInFile,line);++++++++++
+++++}
+++++vInFile.close();
+++++vOutFile.close();
++}

++else+std::cout+<<+"Unable+to+open+file";

++return+0;
}|code-block|syntax|javascript|402055|entityMap^0|0|0|0|0|0|S|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|10|8|@$J|11|K|12|L|M]]|9|@]|A|$]]|$1|N|3|O|5|6|7|13|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|14|8|@]|9|@]|A|$S|T]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

[I am just explaining the command line argument used in Question]

You can provide file name as command line input to the executible, but then you need to open them in your code. 

Like

You have supplied two command line arguments namely inputfile &amp; outputfile

[ <code>App.exe inputfile outputfile</code> ]

Now in your code

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

int main(int argc, char * argv[])
{
 //argv[0] := A.exe
 //argv[1] := inputFile
 //argv[2] := outputFile

 std::ifstream vInFile(argv[1],std::ios::in); 
 // notice I have given first command line argument as file name

 std::ofstream vOutFile(argv[2],std::ios::out | std::ios::app);
 // notice I have given second command line argument as file name

 if (vInFile.is_open())
 {
 std::string line;

 getline (vInFile,line); //Fixing it as per the comment made by MSalters

 while ( vInFile.good() )
 {
 vOutFile &lt;&lt; line &lt;&lt; std::endl;
 getline (vInFile,line); 
 }
 vInFile.close();
 vOutFile.close();
 }

 else std::cout &lt;&lt; "Unable to open file";

 return 0;
}
</code></pre>

blocks|key|402072|text|理解重定向的概念非常重要。重定向标准输入、标准输出和标准错误。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|402073|常见的重定向命令是：|402074|>将命令的标准输出重定向到文件，覆盖以前的内容。
$+command+>+file|unordered-list-item|CODE|402075|>>将命令的标准输出重定向到文件，并将新内容附加到旧内容中。
$+command+>>+file|402076|<将标准输入重定向到命令。
$+command+<+file|402077|%7C将命令的标准输出重定向到另一个命令。
$+command+%7C+another_command|402078|2>将标准错误重定向到文件。
$++command+2>+file
$+command+>+out_file++2>+error_file|402079|2>&1将stderr重定向到stdout被重定向到的同一个文件。
$+command+>+file+2>&1|402080|您可以组合重定向：|402081|#+redirect+input,+output+and+error+redirection
$+command+<+in_file+>+out_file++2>+error_file
#+redirect+input+and+output
$+command+<+in_file+>+out_file
#+redirect+input+and+error
$+command+<+in_file+2>+error_file
#+redirect+output+and+error
$+command+>+out_file++2>+error_file|code-block|syntax|javascript|402082|即使这不是您问题的一部分，当与重定向命令相结合时，您也可以使用其他强大的命令：|402083|sort：按字母顺序排列文本行。|402084|uniq：过滤重复的，相邻的文本行。|402085|grep：搜索文本模式并输出它。|402086|sed：搜索文本模式，修改它，并输出它。|402087|entityMap|0|LINK|mutability|MUTABLE|url|https://www.geeksforgeeks.org/sort-command-linuxunix-examples/|1|https://www.geeksforgeeks.org/uniq-command-in-linux-with-examples/|2|https://www.geeksforgeeks.org/grep-command-in-unixlinux/|3|https://www.geeksforgeeks.org/sed-command-in-unix/^0|2|3|0|0|0|1|P|G|0|0|2|V|H|0|0|1|E|G|0|0|1|K|R|0|0|2|F|I|Y|Z|0|0|4|Y|L|0|0|0|0|0|4|0|4|0|0|0|4|0|4|1|0|0|4|0|4|2|0|0|3|0|3|3|0^^$0|@$1|2|3|4|5|6|7|1Q|8|@$9|1R|A|1S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1T|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1U|8|@$9|1V|A|1W|B|K]|$9|1X|A|1Y|B|K]]|D|@]|E|$]]|$1|L|3|M|5|J|7|1Z|8|@$9|20|A|21|B|K]|$9|22|A|23|B|K]]|D|@]|E|$]]|$1|N|3|O|5|J|7|24|8|@$9|25|A|26|B|K]|$9|27|A|28|B|K]]|D|@]|E|$]]|$1|P|3|Q|5|J|7|29|8|@$9|2A|A|2B|B|K]|$9|2C|A|2D|B|K]]|D|@]|E|$]]|$1|R|3|S|5|J|7|2E|8|@$9|2F|A|2G|B|K]|$9|2H|A|2I|B|K]|$9|2J|A|2K|B|K]]|D|@]|E|$]]|$1|T|3|U|5|J|7|2L|8|@$9|2M|A|2N|B|K]|$9|2O|A|2P|B|K]]|D|@]|E|$]]|$1|V|3|W|5|6|7|2Q|8|@]|D|@]|E|$]]|$1|X|3|Y|5|Z|7|2R|8|@]|D|@]|E|$10|11]]|$1|12|3|13|5|6|7|2S|8|@]|D|@]|E|$]]|$1|14|3|15|5|J|7|2T|8|@$9|2U|A|2V|B|K]]|D|@$9|2W|A|2X|1|2Y]]|E|$]]|$1|16|3|17|5|J|7|2Z|8|@$9|30|A|31|B|K]]|D|@$9|32|A|33|1|34]]|E|$]]|$1|18|3|19|5|J|7|35|8|@$9|36|A|37|B|K]]|D|@$9|38|A|39|1|3A]]|E|$]]|$1|1A|3|1B|5|J|7|3B|8|@$9|3C|A|3D|B|K]]|D|@$9|3E|A|3F|1|3G]]|E|$]]|$1|1C|3|-4|5|6|7|3H|8|@]|D|@]|E|$]]]|1D|$1E|$5|1F|1G|1H|E|$1I|1J]]|1K|$5|1F|1G|1H|E|$1I|1L]]|1M|$5|1F|1G|1H|E|$1I|1N]]|1O|$5|1F|1G|1H|E|$1I|1P]]]]

It is important that you understand the concept of redirection. Redirection reroutes standard input, standard output, and standard error.

The common redirection commands are:

<ul>
<li><code>&gt;</code> redirects standard output of a command to a file, overwriting previous content.

<code>$ command &gt; file</code></li>
<li><code>&gt;&gt;</code> redirects standard output of a command to a file, appending new content to old content.

<code>$ command &gt;&gt; file</code></li>
<li><code>&lt;</code> redirects standard input to a command.

<code>$ command &lt; file</code></li>
<li><code>|</code> redirects standard output of a command to another command.

<code>$ command | another_command</code></li>
<li><code>2&gt;</code> redirects standard error to a file.

<code>$ command 2&gt; file</code>

<code>$ command &gt; out_file 2&gt; error_file</code></li>
<li><code>2&gt;&amp;1</code> redirects stderr to the same file that stdout was redirected to.

<code>$ command &gt; file 2&gt;&amp;1</code></li>
</ul>

You can combine redirection:

<pre><code># redirect input, output and error redirection
$ command &lt; in_file &gt; out_file 2&gt; error_file
# redirect input and output
$ command &lt; in_file &gt; out_file
# redirect input and error
$ command &lt; in_file 2&gt; error_file
# redirect output and error
$ command &gt; out_file 2&gt; error_file
</code></pre>

Even though, it is not part of your question, you can also use other commands are powerful when combined with redirection commands:

<ul>
<li><a href="https://www.geeksforgeeks.org/sort-command-linuxunix-examples/" rel="nofollow noreferrer"><code>sort</code></a>: sorts lines of text alphabetically.</li>
<li><a href="https://www.geeksforgeeks.org/uniq-command-in-linux-with-examples/" rel="nofollow noreferrer"><code>uniq</code></a>: filters duplicate, adjacent lines of text.</li>
<li><a href="https://www.geeksforgeeks.org/grep-command-in-unixlinux/" rel="nofollow noreferrer"><code>grep</code></a>: searches for a text pattern and outputs it.</li>
<li><a href="https://www.geeksforgeeks.org/sed-command-in-unix/" rel="nofollow noreferrer"><code>sed</code></a> : searches for a text pattern, modifies it, and outputs it.</li>
</ul>

For faster input, I read that you can do <code>file-redirection</code> and include a file with the <code>cin</code> inputs already set.

In theory it should be used like following:

<pre><code>App.exe inputfile outputfile
</code></pre>

As far as I understood from C++ Primer book, The following C++ code[1] should be reading <code>cin</code> input from the text file and shouldn't need to any other special indication like[2]

[2]

<pre><code>include &lt;fstream&gt;
ofstream myfile;
myfile.open ();
</code></pre>

[1] The following C++ code...

<pre><code>#include &lt;iostream&gt;
int main()
{
 int val;
 std::cin &gt;&gt; val; //this value should be read automatically for inputfile
 std::cout &lt;&lt; val;
 return 0;
}
</code></pre>

Am I missing something?

C++ file-redirection

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。

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为了获得更快的输入，我看到您可以执行file-redirection，并包含一个已经设置了cin输入的文件。从理论上讲，它的使用应如下所示：App.exe inputfile outputfile据我从C++入门书中了解到，下面的C++ code1应该读取文本文件中的cin输入，而不需要任何其他特殊指示like22in...

问C++文件重定向
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