How can I run `watch` as a background job?

Question

When I run:

watch 'cmd >> output.txt' &

the job gets suspended by the system:

3569 Stopped (tty output)

Is there a workaround?

Answer 1

The purpose of watch is to show the results of a command full-screen and update continuously; if you're redirecting the output into a file and backgrounding it there's really no reason to use watch in the first place.

If you want to just run a command over and over again with a delay (watch waits two seconds by default), you can use something like this:

while true; do
    cmd >> output.txt
    sleep 2
done

Answer 2

I'm not sure about your motivations, but maybe this would be enough?

while true; do sleep 2; cmd >>output.txt; done &

Otherwise, please explain why you really need watch.

Answer 3

tee is your friend. For example, here's how you could show the number of files in the current directory, and append it to count.txt every 2 seconds:

watch 'find . -maxdepth 1 -printf " " | wc -c | tee --append count.txt'

Answer 4

You can use screen command.

http://www.cyberciti.biz/tips/linux-screen-command-howto.html