What to do when Ctrl-C won't kill running job?

Question

Sometimes, processes ignore the SIGINT signal sent by Ctrl-C in Bash. For instance, man and vi. Assuming you don't want to google or read the manual on how to exit the running process, is there any key sequence that will always work (without leaving the terminal)?

Answer 1

Send the SIGQUIT signal with Ctrl+\.

.. $ sleep 10
^\Quit

→ This is equivalent to kill -3 pid. Programs run in user-space don't ignore sigquit.

There is also a set of Magic SysRq keyboard shortcuts. One of the more interesting ones is this: Alt+SysRq+k. It kills every process on the current virtual console. If one of your ttys is completely and utterly broken, this can be used to go back. On the tty running X.org, it can be used to kill X without mercy.

The SysRq key is, on most keyboards, the same as the Print Key. On my notebook, it can be invoked using the Fn key; I.e. Alt→Fn→Print→k in that order.

Here are some of the basic process management shortcuts:

• Ctrl+Z: pause a process (plus bg to resume in the background, fg to raise to foreground)
• Ctrl+C: politely ask the process to shut down now
• Ctrl+\: mercilessly kill the process that is currently in the foreground
• Alt+SysRq+s: Write data to disk (always do this before killing anything important)
• Alt+SysRq+s, k: mercilessly kill all current processes on a given virtual console
• Alt+SysRq+s, b: mercilessly reboot without unmounting,
• Alt+SysRq+r, e, i, s, u, b: Safely reboot even if the system is utterly broken,

Note: Ctrl+Z, in contrast to Ctrl+C and Ctrl+\, also works for man, vi, less, and the like.

When in doubt, the follwing procedure will almost always work:

~$ sleep 10
^Z
[5]+  Stopped              sleep 10
~$ ps
  PID TTY          TIME CMD
 4804 pts/0    00:00:00 bash
 6207 pts/0    00:00:00 sleep
 6208 pts/0    00:00:00 ps
~$ kill -9 6207
[5]+  Killed                  sleep 10
~$ 

^Z of course indicates that Ctrl+Z has been pressed.

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For a more in-depth look at Shells and Terminals, also see my answers on:

• What are shells?
• Why is a virtual terminal "virtual", and what/why/where is the "real" terminal?

Answer 2

You can try Ctrl+\

Answer 3

Sometimes the CTRL+C is getting sent to the wrong program or input channel. This is especially common with editors such as vi, with commands with piped output, complex bash commands involving loops, etc.

A simple, quick solution is to suspend the job CTRL+Z and then kill it by job number: kill %1 or kill -9 %1, etc.

Answer 4

• Try one of these:

  Ctrl+4

  Ctrl+\

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• Or:

  Ctrl+Z and then run:

  kill %1

Where %1 is the number of job which was returned when you pressed Control-Z. Add -9 to force the kill.

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When you're in text console, you could also try: Ctrl-SysRq. The kernel should kill the process.

Or SysRq-k, kill all processes on the current virtual console (can kill X and svgalib programs as well).

Note: When magic SysRq keys are used to kill a frozen graphical program, the program has no chance to restore text mode. This can make everything unreadable.

See: Magic SysRq key and its command combinations.

Answer 5

It's possible, that you changed the shortcut of copy from:

CTRL+SHIFT+C

To

CTRL+C

That way, when you try to kill a process, the CTRL+C doesn't work.

Try to replace the copy shortcut to CTRL+SHIFT+C.

Answer 6

To quit from man, use q To leave vi use :q

Answer 7

Open Terminal → Preferences → Shortcuts and search if by mistake you have replaced any key with Ctrl+C.

Answer 8

Try Ctrl+Alt+Backspace

If you are using ubuntu 10.04 you wanna enable this key to work.

To enable Control-Alt-Backspace

Goto System-->Preferences-->Keyboard

Select the Layouts tab and click on the Layout Options.

Select Key sequence to kill the X server and enable Control + Alt +Backspace.

Note:

Pressing Ctrl-Alt-Backspace will restart your X server.