freopen stdout and console

Question

Given the following function:

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

Redirects stdout into a file, how do I make it so stdout redirects back i

Answer 1

You should be able to use _dup to do this

Something like this should work (or you may prefer the example listed in the _dup documentation):

#include <io.h>
#include <stdio.h>

...
{
    int stdout_dupfd;
    FILE *temp_out;

    /* duplicate stdout */
    stdout_dupfd = _dup(1);

    temp_out = fopen("file.txt", "w");

    /* replace stdout with our output fd */
    _dup2(_fileno(temp_out), 1);
    /* output something... */
    printf("Woot!\n");
    /* flush output so it goes to our file */
    fflush(stdout);
    fclose(temp_out);
    /* Now restore stdout */
    _dup2(stdout_dupfd, 1);
    _close(stdout_dupfd);
}

Answer 2

An alternate solution is:

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

Per wikipedia "CON" is a special keyword which refers to the console.

Answer 3

After posting the answer I have noticed that this is a Windows-specific question. The below still might be useful in the context of the question to other people. Windows also provides _fdopen, so mayble simply changing 0 to a proper HANDLE would modify this Linux solution to Windows.

stdout = fdopen(0, "w")

#include <stdio.h>
#include <stdlib.h>
int main()
{
    freopen("file.txt","w",stdout);
    printf("dupa1");
    fclose(stdout);
    stdout = fdopen(0, "w");
    printf("dupa2");
    return 0;
}