Ubuntu – How to automatically execute a command every time a certain command terminates

aptcommand lineexecute-command

Example: Once the add-apt-repository process has terminated, immediately run apt-get update – without having to enter the command manually.

Is there a way to do this? Is it possible to set such a combination without the use of the sudo password? (although I don't mind either way)

I'm asking the following: How can I link two commands together, so that whenever I execute a particular command, it always executes the the linked command after it?

Best Answer

There are various issues hooking into this with an alias or a simple bash function, but you can write a little wrapper for a command and stick it in /usr/local/bin which takes priority in your path.

This is a little trick to create a script and chmod it at the same time.
It'll dump an executable wrapper script in /usr/local/bin/add-apt-repository.

sudo install -b -m 755 /dev/stdin /usr/local/bin/add-apt-repository << 'EOF'
/usr/bin/add-apt-repository "$@"
apt-get update

To reverse this, just delete /usr/local/bin/add-apt-repository.

If you want to do something fruitier (like linking apt-get install and apt-get update so you always update before installing), we just need to expand the script to look at the arguments.

sudo install -b -m 755 /dev/stdin /usr/local/bin/apt-get << 'EOF'
if [ "$1" = "install" ] ; then
    /usr/bin/apt-get update
/usr/bin/apt-get "$@"

Though consider that this will run an update before every apt-get install call. This might sound helpful but could be really tedious in practice.