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c++linuxpipefile-descriptor

how to get back stdout after piping it with dup?

int mypipe[2];
pipe(mypipe);
int dupstdout=dup2(mypipe[1],1);
cout<<"hello";//not printed on terminal
fflush(stdout);

now how to print again on terminal or redirect mypipe[0] to stdout?

Solution 
  • #include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

int main() {
    int mypipe[2];
    pipe(mypipe);
    int dupstdout=dup2(mypipe[1], 1);
    printf("hello");//not printed on terminal
    fflush(stdout);

    close(dupstdout);

    int fd = open("/dev/tty", O_WRONLY);
    stdout = fdopen(fd, "w");

    printf("hello again\n");
}

    Anyway, it's better to not close stdout.

    If a descriptor passed as a second argument to dup2() is already opened, dup2() closes it ignoring all errors. It's safer to use close() and dup() explicitly.