To pause or stop a process, we can either use keyboard shortcuts or send a signal to our process. Let's look at the keyboard shortcuts first, then dive into what sending signals is all about.
To interrupt a process, press ctrl+c. This interrupts the program by sending it a
INT (interrupt) signal.
To pause a process, press ctrl+z. This sends the program a TSTP command (Terminal Stop).
This is especially useful if you want to pause a program and come back to it later. For example, we could have Python running, then press ctrl+z. This will place Python to the background. If you want to return to Python, simply type
fg %1, and you'll be back where you left off.
Keyboard shortcuts are simply a convenient way to sending signals to jobs in our foreground.
As we have just seen, ctrl+c sends an
INT signal (for interrupt), and ctrl+z sends a
TSTP signal (terminal stop).
Besides sending an
INT (interrupt) or
TSTP (terminal stop) signal, there are many more signals that we can use with the
To use this command, specify a signal as the option, with the PID or the jobspec.
$ kill -s signal pid
If no signal is mentioned, the default signal is
Here is a list of Unix signals, which you may also see with the
kill -l command. When specifying the signal, you may either use the shortened word form, or its integer value. We've included an asterisk next to a signal to denote the most commonly used signals.
Here are a few examples with the above signals.
$ kill -3 13569 # Quits out of process with PID 13569 $ kill -INT 1239 # Interrupts process with PID 1239.
Even without the
kill command, a process can be shutdown. For instance, if you
ssh into a computer, start up a process, then logout, a SIGHUP command will be sent out, and your program will be shut down.
To prevent your process to shutting down, precede the process invokation with the
$ nohup python3 MyRedditBot.py
To shut down multiple processes, use the
killall command. This command uses a process' name instead of its PID. You may also place in the
-i option so that the terminal asks for confirmation before shutting down a process.
The following command will terminal all programs with the name
$ killall gedit
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