在C中没有成功使用popen()? [英] unsuccessful use of popen() in C?

问题描述

我可以运行以下命令

xwd -root | xwdtopnm | pnmtojpeg > screen.jpg

在Linux下的终端中，它将产生我当前屏幕的屏幕截图.

in a terminal under linux and it will produce a screenshot of my current screen.

我尝试对代码执行以下操作:

I try to do the following with the code:

#include <stdio.h>
#include <stdlib.h>
int main()
{
   FILE *fpipe;
   char *command="xwd -root | xwdtopnm | pnmtojpeg";
   char line[256];

   if ( !(fpipe = (FILE*)popen(command,"r")) )
   {  // If fpipe is NULL
      perror("Problems with pipe");
      exit(1);
   }

   while ( fgets( line, sizeof line, fpipe))
   {
      //printf("%s", line);
      puts(line);
   }
   pclose(fpipe);
}

然后我编译并运行程序./popen > screen.jpg，但生成的文件screen.jpg无法识别.如何做到这一点，以便我可以正确地浏览程序?

then I compile and run the program ./popen > screen.jpg but the resulting file screen.jpg is unrecongizable. How can I do this so that I can pipe through my program correctly?

推荐答案

您不应使用fgets和puts处理二进制数据. fgets将在看到换行符时停止.更糟糕的是，puts将输出额外的换行符，并且每当遇到\ 0时它也会停止.改用fread和fwrite.

You shouldn't use fgets and puts for dealing with binary data. fgets will stop whenever it sees a newline. Worse, puts will output extra newlines and it will also stop whenever it runs into a \0. Use fread and fwrite instead.

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