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Amandasaurus
Asked: 2010-01-23 07:09:28 +0800 CST

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

  • 772

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.

linux unix bash command-line-interface job-control

6 Answers

  1. Best Answer
    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.

    • 42

  2. 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.

    • 37

  3. 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.

    • 28
    1. Press Ctrl-Z to suspend the script ;
    2. kill %%

    Credits, explanations and more details in this answer.

    • 12

  5. 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/
    • 8

  6. 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.

    • 1