Question

I am working with a multi-thread program.

First I redirect my stdout to a certain file. No problem there (I used dup2(fd, 1) where fd is the file descriptor for the file).

Afterwards, I need to redirect my stdout to the terminal again.

My first approach:

      /*Declaration*/
      fpost_t  stream_sdout;
      /*code*/
      if ( fgetpos( stdout, &stream_sdout) == -1 )
          perror(Error:);

It says illegal seek.
No idea why this is happening.
But if I get this to work, then I only need to use fsetpos(stdout, &stream_stdout) and it should work.

My second idea, was to to copy the stdout using dup2(stdout, 4) to the file descriptor table, at position 4. But that ain’t working either.

How can I switch the standard output back to its original destination (terminal, pipe, file, whatever)?

Answer 1

#include <unistd.h>

...

int saved_stdout;

...

/* Save current stdout for use later */
saved_stdout = dup(1);
dup2(my_temporary_stdout_fd, 1);

... do some work on your new stdout ...

/* Restore stdout */
dup2(saved_stdout, 1);
close(saved_stdout);