kill terminates the designated process IDs (shown under the PID heading in the ps listing). If you do not know the process ID, do a ps first to display the status of your processes.
In the following example, the "sleep n" command simply causes a process to "go to sleep" for n number of seconds. We enter two commands, sleep and who, on the same line, as a background process.
(sleep 60; who)& 21087 %
psPID TTY TIME COMMAND 20055 4 0:10 sh 21087 4 0:01 sh 21088 4 0:00 sleep 21089 4 0:02 ps %
kill 21088Terminated % tom tty2 Aug 30 11:27 grace tty4 Aug 30 12:24 tim tty5 Aug 30 07:52 dale tty7 Aug 30 14:34
We decided that 60 seconds was too long a time to wait for the output of who. The ps listing showed that sleep had the process ID number 21088, so we used this PID to kill the sleep process. You should see a message like "terminated" or "killed"; if you don't, use another ps command to be sure the process has been killed.
The who command is executed immediately, since it is no longer waiting on sleep; it lists the users logged into the system.
Some processes can be hard to kill. If a normal kill of these processes is not working, enter "kill -9 PID". This is a sure kill and can destroy almost anything, including the shell that is interpreting it.
In addition, if you've run an interpreted program (like a shell script), you may not be able to kill all dependent processes by killing the interpreter process that got it all started; you may need to kill them individually. However, killing a process that is feeding data into a pipe will generally kill any processes receiving that data.