Sooner or later you will want to kill a process, whether it be some code executed in the background that is taking too long or simply a program that is misbehaving.
If the code has been executed by the user in the background, then one can use the jobs command with the kill command:
michael@michael-laptop:~$ jobs [1]+ Running ./test & michael@michael-laptop:~$ kill -9 %1 michael@michael-laptop:~$ [1]+ Killed ./test
The second term specifies which signal to send, as specified in CTRL + C sends the SIGINT interrupt signal to the program and CTRL + Z sends the SIGSTOP pause signal. The -9 sends the SIGKILL signal, which is slightly more forceful than the default SIGTERM which is obtained by -15 or omitting this field. SIGKILL forces the program to end immediately whereas SIGTERM can be intercepted or ignored by the program. The latter is the gentler approach as it can allow the program to clean itself up before finishing. ?using the latter would have produced this line of code [1]+ Terminated ./test as opposed to Killed
top command
Alternatively, you can use the top command to display processes in order of CPU demand. N.B. It is called “top” because only the top most demanding processes are shown.
top - 12:26:34 up 23 days, 12:39, 2 users, load average: 8.00, 8.01, 8.05 Tasks: 152 total, 10 running, 142 sleeping, 0 stopped, 0 zombie Cpu(s): 64.4%us, 0.2%sy, 0.0%ni, 35.4%id, 0.0%wa, 0.0%hi, 0.1%si, 0.0%st Mem: 24732896k total, 24581112k used, 151784k free, 531980k buffers Swap: 3999676k total, 9080k used, 3990596k free, 21636732k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2447 laemmel 20 0 122m 111m 972 R 100 0.5 9880:20 BD-concn-semifl 2486 lindon 20 0 58676 40m 1492 R 100 0.2 9875:24 hing 4053 laemmel 20 0 122m 111m 972 R 100 0.5 9672:33 BD-concn-semifl 7782 sturm 20 0 19496 7100 1220 R 100 0.0 1520:41 tfpulling 20031 sturm 20 0 23384 10m 1220 R 100 0.0 5330:51 tfpulling 26339 sturm 20 0 22616 10m 1220 R 100 0.0 4374:08 tfpulling 30841 glaser 20 0 44.5g 473m 344m R 100 2.0 10974:30 hoomd 1093 sturm 20 0 58764 45m 1184 R 100 0.2 10176:04 tfpulling
Within top, you can press k (for kill) and then enter the PID (process ID) of the process you would like to kill. To exit top, press q. If you know the PID, which you can get from top, you can use the kill command in a regular terminal by entering kill -9 PID