Hands-On System Programming with Linux

Wait scenario #1

It's the simple case (one we've already come across): a process forks, creating one child process. The parent subsequently issues the wait API; it now blocks on a status change in it's child process; recall, the possible status changes the child can possibly go through are these:

• State transition from running (R): dead; that is to say, the child terminates (normally/abnormally)
• State transition from running/asleep (R|S|D) to stopped state (T); that is to say, it receives a signal causing it be stopped
• State transition from stopped state (T) to ready-to-run (R); that is to say, from a stopped state to a ready-to-run state

(The state transitions and the letters representing the process state are covered in Chapter 17,