Peek-a-Boo Process Actions

Peek-a-Boo allows you to control and manipulate processes in several ways. These can be initiated either from Peek-a-Boo’s Manage menu or from the process list’s toolbar.

Hide Process will hide all windows of the selected process.

Bring to Front brings the selected process to the front. You can also double-click on a process to bring it to the front.

Reveal in Finder will open the folder in which the process’ executable file is located.

Kill Process tells the selected process to quit. Peek-a-Boo uses an escalating mechanism to kill the process:

  • If the process you’re killing is an application (OS X Application or Classic Application), it starts out with a ‘quit’ Apple Event. If that fails to kill the process, then next time you choose Kill Process will try the next method. (If the process is a daemon or Darwin Process it will immediately try the next method.)
  • Peek-a-Boo uses a Unix “kill” command from the current user, using the “TERM” signal. This is a gentle enough signal that many Unix programs will catch it elegantly and clean themselves up before they quit.
  • If this fails, Peek-a-Boo’s daemon generates a Unix “kill” command. (This step uses the “TERM” signal and the daemon’s permissions.) If this fails to kill the process, then the next time you choose Kill Process will try the final method.
  • Peek-a-Boo will finally resort to a Unix “kill” command, passing a “KILL” signal (-9) and the daemon’s permissions.

If the selected process fails to quit after you choose Kill Process once, choose it again and Peek-a-Boo will try the next step in this escalating mechanism.

Halt Process sends a SIGSTOP message to the process, freezing it until it is continued.

This can be a dangerous command. If a process such as the Window Manager (or Peek-a-Boo itself) is halted, it can effectively freeze your entire user interface without an easy way to recover.

If you halt a process, the process list will show a “halted” icon in the indicator column.

Continue Process sends a SIGCONT message to a halted process, unfreezing it so it continues.

Halt and Continue may be used if, for example, a process is using a lot of CPU power and you just want to “pause” it for a few moments.

  Sample Process will invoke OS X’s sample tool for five seconds, after which it will report on how that process was using time. This can be tremendously valuable to developers analyzing CPU usage.



High, Normal, Low Priority will “renice” the process; you can adjust how much CPU time each process consumes.

With OS X’s method of time-slicing between all processes (and threads) which want CPU time (especially in contrast to OS 9’s cooperative multitasking), it’s possible that changing a process’ priority will not show an obvious result. If there’s enough CPU time for every process which is requesting time, then generally changing priority won’t show an effect. The environment where adjusting a process’ priority will show the most obvious results is where the CPU is maxed out so OS X is forced to choose between several processes that want CPU time. In this environment, it is easy to see the difference between a High Priority (reniced to -20) process and a Low Priority (reniced to +20) process.