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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Program: REDIR.C
Author: F. PIETTE (2:293/2201.135)
Object: Demonstration of the output redirection
Creation: Augustus 2, 1991
Updates:
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#include <stdio.h>
#include <stdlib.h>
#include <io.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
void main(void)
{
int old_fh;
int new_fh;
fprintf(stdout, "This goes to the original standard output\n");
/* Duplicate the stdout file handle to restore it later */
old_fh = dup(fileno(stdout));
if (old_fh == -1) {
fprintf(stderr, "dup error\n");
exit(1);
}
/* Open the new file for output */
if ((new_fh = open("redir.txt", O_CREAT | O_TRUNC | O_WRONLY,
S_IREAD | S_IWRITE)) == -1) {
fprintf(stderr, "Unable to open redir.txt\n");
exit(1);
}
/* Duplicate the new handle to stdout */
dup2(new_fh, fileno(stdout));
/* We don't need new_fh any more, so close it */
close(new_fh);
/* stdout is now redirected, let's try it */
fprintf(stdout, "This goes to redir.txt file !\n");
/* If you run a program using spawn(), the child program will have */
/* its output redirected to REDIR.TXT file ! */
/* Now let's restore stdout to its original state */
fflush(stdout); /* First flush the outut buffer */
/* Then duplicate the original file handle to stdout */
dup2(old_fh, fileno(stdout));
/* Let's try if we canceled the redirection */
fprintf(stdout, "Back to original stdout\n");
exit(0);
}
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