Hands-On System Programming with Linux

Experiment 1 – on the CLI, no frills

Follow the simple steps here:

1. Fire up a shell (a Terminal window, typically, on a GUI-based Linux)
2. In the window, or more precisely, at the shell prompt, type this:

   $ exec ps

What do you notice? Can you explain it?

Hey, come on, please try it out first, and then read on. Yes, the terminal window process is the predecessor here; upon an exec it's overwritten by the successor process ps, which does its work and exits (you probably did not see the output as it disappeared too quickly). ps is the successor process, and, of course, we cannot return to the predecessor (the Terminal window)—ps has literally replaced its VAS. Thus, the Terminal window effectively disappears.