如何将stdout重定向到ANSI C中的字符串

Question

I am a beginner in learning C language :-)

I have searched how to solve this in stackoverflow, but nothing I can understand. :-(

Before posting this thread, I always redirect stdout to a file, and then read it to a string by using fread

system ("print.exe > tempfile.tmp");
FILE *fp = fopen ( tempfile.tmp , "rb" );
char Str[Buf_Size];
fread (Str,sizeof(char),Buf_Size,fp);

If doing so, it'll waste lots of time in File I/O.

How can I redirect stdout to a string in C Language without redirecting to a tempfile?

Is it possible? Thanks.

Environment: Windows and GCC

Answer 1

In Unix you would:

• Create a pipe
• fork a child process
• The parent:
  • Closes the writing end of the pipe
  • Starts reading from the pipe
• The child:
  • Closes the reading end of the pipe
  • Closes stdout
  • dup2 's the write-end pipe to fd 1
  • exec 's the new program

Answer 2

The stdout can be redirected via popen routine:

#include <stdio.h>
...


FILE *fp;
int status;
char path[PATH_MAX];


fp = popen("ls *", "r");
if (fp == NULL)
    /* Handle error */;


while (fgets(path, PATH_MAX, fp) != NULL)
    printf("%s", path);


status = pclose(fp);
if (status == -1) {
    /* Error reported by pclose() */
    ...
} else {
    /* Use macros described under wait() to inspect `status' in order
   to determine success/failure of command executed by popen() */
   ...
}