Most of the time programs running on your Mac behave, but occasionally they freeze up and stubbornly refuse to close or respond. Usually you can force an application to quit by pressing Option+Command+Escape, selecting the wayward program, and clickng the Force Quit button. If that fails there is another trick to close a frozen program. Morbidly enough it’s a command called kill.
The kill command is very powerful and therefore needs a very specific target, so you don’t kill the wrong thing. One way to identify the program to kill is through the Activity Monitor from the Utilities folder in Applications. Opening the Activity Monitor will show you a detailed list of everything that is running on your computer. Scroll down the list until you find your misbehaving program (Firefox in the example below). Next, take note of the PID or Process ID, a unique number assigned to a program each time it starts running. Now that you have the PID (in this example 681), you can sic kill on it. Open the terminal, again from the Utilities folder in Applications. Once it’s open type:
kill [the PID of your frozen program]
Then press Enter.Usually that forces your program to close. If it doesn’t, you can always turn off your computer by holding down the power button, or get in touch with IT by sending an email to: helpdesk [at] uua.org