Despite a tiny setback, I managed to regraded your Lab 4.  Grades have been sent to your SoC email account (with @comp.nus.edu.sg address) which you can read by logging into sunfire and run mutt or pine, or by logging into SoC webmail.

One more common error emerges from this regrading.  I noticed many of you call either wait() or waitpid() without specifying the PID of the process you are waiting for (in the case of foreground process).  This can cause a problem, as any of the previously running background process can interrupt the wait.