runwhenidle is a Linux utility that can be used to run a computationally or IO-intensive program when user is not in front of the computer, pausing it once the user is back, resuming once the user left, often without requiring adaptation from the program being ran.

runwhenidle runs a command given to it, pauses it if the user is active by sending SIGTSTP to the command, when the user activity stops, runwhenidle resumes the command by sending it SIGCONT signal. It then checks once per second if user activity has resumed, and once it is, pauses the command again.

runwhenidle uses XScreenSaverQueryInfo() to check when last user activity happened therefore a running X server is required. Wayland is not currently supported.

Compiling

Make sure you have gcc, make and libxss-dev installed. Run make release. This should produce a binary file runwhenidle in the project directory.

If you want to install it system-wide, run sudo make install or simply sudo cp ./runwhenidle /usr/bin.

I will package this for popular distros in case there is demand.

Usage

runwhenidle [--timeout|-t timeout_value_in_seconds] [--verbose|-v] [--quiet|-q] shell_command_to_run

--timeout or -t specifies how many seconds of user inactivity are enough to resume the command. Default value is 300/5 minutes.

--verbose or -v adds additional debug output --quiet or -q suppresses all the output from runwhenidle and only displays output from the command that is running.

Example 1:

runwhenidle -t 100 -v "cp /filea /fileb"

Run the cp command and pause it while user is active. When user is inactive for 100 seconds, resume the command. Output debug information to stderr.

Example 2:

runwhenidle --timeout=300 -q "cat /dev/zero"

Run the cat /dev/zero command and pause it while user is active. -q option makes sure runwhenidle doesn't output anything other than the output of cat /dev/zero.

Building Ubuntu/Debian package:

Make sure you have docker installed and run:

make debian-package

The .deb file will be generated in package-build/ directory.