重定向stdout

最新推荐文章于 2023-12-26 15:34:51 发布

转载最新推荐文章于 2023-12-26 15:34:51 发布 · 715 阅读

本文详细介绍了如何在C程序中使用freopen()函数将标准输出重定向到指定文件，并在适当的时候恢复默认输出。通过示例代码演示了重定向输出到文件和恢复到控制台的方法。

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Summary

This article explains how to redirect stdout to a file from a C program, then restore the original stdout at a later point in the same program. The C function typically used to redirect stdout or stdin is freopen(). To redirect stdout to a file called FILE.TXT, use the following call:

   freopen( "file.txt", "w", stdout );

This statement causes all subsequent output, which is typically directed towards stdout, to go to the file FILE.TXT.

To return stdout to the display (the default stdout), use the following call:

   freopen( "CON", "w", stdout );

In both of these cases, check the return value of freopen() to make sure that the redirection actually took place.

Below is a short program to demonstrate the redirection of stdout:

Sample Code


// Compile options needed: none

#include <stdio.h>
#include <stdlib.h>

void main(void)
{
   FILE *stream ;
   if((stream = freopen("file.txt", "w", stdout)) == NULL)
      exit(-1);

   printf("this is stdout output\n");

   stream = freopen("CON", "w", stdout);

   printf("And now back to the console once again\n");
}

This program assumes that stdout is to be redirected toward the console at the end of the program.