Linux Pocket Guide

Killing a Command in Progress

If you’ve launched a command from the shell running in the foreground, and want to kill it immediately, type ^C. The shell recognizes ^C as meaning, “terminate the current foreground command right now.” So if you are displaying a very long file (say, with the cat command) and want to stop, type ^C:

$ cat bigfile
This is a very long file with many lines. Blah blah blah
blah blah blah blahblahblah ^C
$

To kill a program running in the background, you can bring it into the foreground with fg and then type ^C, or alternatively, use the kill command (see Controlling Processes).

In general, ^C is not a friendly way to end a program. If the program has its own way to exit, use that when possible. You see, ^C kills the program immediately, not giving it any chance to clean up after itself. Killing a foreground program may leave your shell in an odd or unresponsive state, perhaps not displaying the keystrokes you type. If this happens:

1. Press ^J to get a shell prompt. This produces the same character as the Enter key (a newline) but will work even if Enter does not.

2. Type the word reset (even if the letters don’t appear while you type) and press ^J again to run this command. This should reset your shell.

^C works only when typed into a shell. It will likely have no effect if typed in a window that is not a shell window. Additionally, some programs are written to “catch” the ^C and ignore it: an example is the text editor emacs.