Bash Loop - How to stop the loop when I press Control-C inside a command?

Question

I am rsyncing a few directories. I have a bash terminal open and am executing something like this:

for DIR in * ; do rsync -a $DIR example.com:somewhere/ ; done

However if I want to stop the whole things, I press Control-C. That stops the rsync, but then it keeps going to the next one. In this case I realize what has happened and then just press Control-C like a madman until things work again.

Is there some way to 'fix' this. I want it so if I have a loop like that, and press Control-C, that it will return me to my bash shell.

Dennis' answer is the right one, but you if you didn't do that, you don't have to 'press it like a madman', just hold it and let the keyboard repeat handle it :-) — Kyle Brandt, Jan 22 '10 at 15:52

score 48 · Accepted Answer · answered Feb 03 '10 at 19:03

48

for DIR in * ; do rsync -a $DIR example.com:somewhere/ || break; done

This will also exit the loop if an individual rsync run fails for some reason.

answered Feb 03 '10 at 19:03

Kenster

2,162

8

Additional tip: if you're in a nested loop, and want to completely terminate, use break 2 (or replace "2" with the number of nested loops you want to terminate). – Dolan Antenucci Jan 23 '13 at 20:33

score 40 · Answer 2 · answered Jul 16 '10 at 00:17

40

To expand on Dennis' answer, your code might look like:

trap "echo Exited!; exit;" SIGINT SIGTERM

For a working example (that happens to involve rsync), check out http://gist.github.com/279849.

answered Jul 16 '10 at 00:17

Ian Greenleaf Young

659

Thanks, this is a generic solution that worked for me – wi1 Jul 30 '18 at 15:14
2

Best answer I think. Trapping both SIGINT and SIGTERM seems to more-consistently kill an infinite while loop than trapping SIGINT alone. UPDATE: eh, maybe not. I'm not sure. I still get some occasions where I have to hit Ctrl + C twice! I'm not sure why. – Gabriel Staples Dec 09 '21 at 19:31
The OP said they were running in a shell, not a shell script. Therefore this will not work. – Oliver Feb 03 '23 at 21:10

score 30 · Answer 3 · edited Jul 02 '18 at 18:57

30

You can set a trap for Control-C.

trap <command> SIGINT

will execute the command when Control-C is pressed. Just put the trap statement somewhere in your script at a point where you want it to become effective.

edited Jul 02 '18 at 18:57

Ondra Žižka

444

answered Jan 22 '10 at 15:16

Dennis Williamson

62,879

1

Example: to force an exit with code 2 whenever Ctrl + C is pressed: trap 'exit 2' SIGINT – Gabriel Staples Nov 18 '21 at 23:31
Even better: also print Ctrl + C just prior to exiting with return code 2: trap 'printf "%s\n" "Ctr + C"; exit 2' SIGINT – Gabriel Staples Nov 18 '21 at 23:35
I can also confirm that SIGINT alone doesn't always seem to work to kill an infinite while loop. Doing trap <cmd> SIGINT SIGTERM, as this answer shows, seems to work better. – Gabriel Staples Dec 09 '21 at 19:30
1

The OP said they were running in a shell, not a shell script. Therefore this will not work for the OP question. – Oliver Feb 03 '23 at 21:10
@Oliver: The OP is running a loop. That is "script-like". – Dennis Williamson Feb 04 '23 at 00:01
@denniswilliamson There's a big difference between exiting a loop and exiting a script. What command will you run to break the loop in a shell (not a shell script), without exiting the shell? – Oliver Feb 04 '23 at 18:11
@DennisWilliamson: OP question: "I have a bash terminal open" – karatedog Jul 20 '23 at 10:13

score 18 · Answer 4 · edited Apr 13 '17 at 12:37

18

Press Ctrl-Z to suspend the script ;
kill %%

Credits, explanations and more details in this answer.

edited Apr 13 '17 at 12:37

Community

1

answered Aug 03 '14 at 10:29

Skippy le Grand Gourou

1,265

This is great because it works "post facto" when you want to interrupt a long-running loop you already started. – Nick Matteo Sep 23 '19 at 17:06
the best answer, thank you! – Kostanos Nov 30 '19 at 17:51
This is the best solution because it works even if you forget to add the || break (@kenster answer) or the parentheses (@amphetamachine answer) – Oliver Feb 03 '23 at 21:11

amphetamachine · Answer 5 · 2023-01-24T17:51:47.733

10

When you put a string of commands inside parentheses, the string will act as a single process, and will receive the SIGINT and terminate when you hit Ctrl-C:

(for DIR in * ; do rsync -a "$DIR" example.com:somewhere/ ; done)

But! In the case of the rsync command, it allows multiple sources, so the code you wrote would be better-written as:

rsync -a * example.com:somewhere/

edited Jan 24 '23 at 17:51

answered Feb 22 '11 at 04:06

amphetamachine

862

This should be at the top. Cheers! – Ammaro Jan 26 '22 at 19:17

score 1 · Answer 6 · answered Mar 04 '14 at 15:53

I tend to put another command in my loop that can easily be interrupted. It requires two ctrl-C's to be pressed.

for DIR in * ; do rsync -a $DIR example.com:somewhere/ ; sleep 1 ; done

It's not such a great solution for this rsync, which you probably want to run quickly. But it does work well for other loops, like this one:

while true ; do ping -c 10 example.com ; sleep 1 ; done

This loop will re-lookup the address of example.com every time through the loop, which is useful if you're watching for a DNS change.

Bash Loop - How to stop the loop when I press Control-C inside a command?

6 Answers6