Question

Is there a difference between having the following code at the begining of program ‘progX’

if(daemon(0, 0) == -1)
{
    printf("daemon error: %s", strerror(errno));
}

or running ‘progX’ via the command: progX & 2>/dev/null 1>/dev/null 0>/dev/null

Answer 1

daemon() does several things:

• Re-parents the process to init by forking and then exiting the parent. Look in the ps list and you’ll see that daemons are owned by PID 1.
• Calls setsid().
• Changes directory to /.
• Redirects standard in, out, and error to /dev/null.

Your redirections handle the last action but not the rest.