How to discard the output from a system command?

Question

I recently wrote this code to execute system command in C. I just want to measure time performed by this system command.

However, I don't want the output results to be displayed upon executing this program.

#include <stdio.h>
int main(int argc, char* argv[])
{
    system("ls");
    return 0;
}

How do I discard the output from the system command?

Answer 1

If you want to measure time by the system command, you can redirect standout and stderr in the system call. Not sure this is the most elegant, but it works:

#include <stdlib.h>
#include <stdio.h>
int main() {
    system("ls >/dev/null 2>&1");
}

Note that you need the <stdlib.h> headers for system.

Answer 2

When you call system() from C, a shell is invoked to interpret your command. This means you can use shell redirects:

system("ls > /dev/null");

and if you want errors to also be suppressed

system("ls > /dev/null 2>&1");

However, due to the overhead of running a shell and the fragility of constructing shell commands, it's better to avoid system() when you can.