How to Kill a Process in Unix

A computer process is a computer program that is executing and has a unique process identification or PID. On the Unix Operating System (OS), a process may be running in the background, foreground, or be in a suspended state. On Unix, the OS shell will not return the prompt to the end-user until the current process that is executing finishes. As a result, many processes that take a significant amount of time to run and keep you from using the Unix console until it finishes running. A common task that arises for Unix users is to kill or background a process in order to conduct other tasks on the computer. In order to about or kill a process a signal has to be sent via keystroke or the Unix kill command.

Steps to Kill a Unix Process with a Single Keystroke

Step 1 – Enter the following command to get specific information on the running process on your computer:

% ps

Step 2 – Depress the “RUB” or “DEL” key if your computer keyboard does not have the “RUB” key and the “_” key at the same time. This will send the interrupt signal to the executing process.

Step 3 – When using the keystroke method to kill a Unix process, you will want to remove the “core” file saved to the computer’s hard drive as a result of using the command. To do so, enter the following command to remove the file:

rm -f core

Steps to Kill a Unix Process with the “Kill Command”

Step 1 – Enter the “ps” command as outlined above to retrieve the PID for the process that you need to kill on Unix. For example,

ps myProcess

will return something similar to:


1234 dz07 0:45 edit myBook

1235 dz07 0:37 -csh

Step 2- Enter the following command to kill the first process listed in the example in step 1:

kill -1 1234

to kill the second process that is active enter:

kill -1 1235

Step 3 – If the Kill -1 switch does not work, you may need to use the -9 argument to clear the process from your computer:

kill -9 1234

kill -9 1235

Step 4 – You can alternatively kill all instances of a given process by using the killall command. The syntax for this command is:

killall <pname>

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  • Xagyg

    I usually use – in this order
    kill something       # i.e. kill -15 something (15 is software interrupt)
    kill -1 something   # (1 is terminal line hangup)
    kill -2 something   # (2 interrupt program)
    kill -3 something   # (3 quit program)
    kill -9 something   # (9 destroy) – last resort
    All signals prior to 9 gives the process some chance to clean up. If none of them terminate the process use the sledgehammer (-9).