Shell – Checking if a specific key is pressed in shell script

shell-script

Is there a way I can check if a specific key is pressed in a shell script which is running in background. Consider I am running a shell script which has to play a play list of songs as soon as I press a key or combinations of 2 or 3 keys. This shell script will be added to crontab , so it won't be running in terminal. So is it possible to capture the keys pressed in this shell script?

Best Answer

Your requirements are not very much clear. But if I understand correctly, I would suggest you to first try out autokey-gtk. It is a python based application in which you can write your scripts in Python which will be executed whenever you press a pre-defined set of keys. See if this fits your need.

Then, if you want to do manually, there are essentially two ways:

Solution#1 : Keylogger Approach

You can write a script which would keep on logging your keyboard keys and initiate an event whenever a certain combination is pressed. For logging keys, you could look at the code of pykeylogger.

Solution#2 : Keybinder Approach

First of all you need to bind your keys using some method. One of the methods is using keybinder. Or you could simply bind your keys using "Keyboard Shortcuts" in your settings. Now, whenever you press a certain set of keys, a script would run which will write some text into a certain XYZ file in you home folder.

In the background, your script which was started using crontab would be reading this XYZ file every 1 second. According to the content of the file, this script will initiate different actions.

Related Solutions

Shell Script – How to Exit Shell Script from a Subshell

You could kill the original shell (kill $$) before calling exit, and that'd probably work. But:

it seems rather ugly to me
it will break if you have a second subshell in there, i.e., use a subshell inside a subshell.

Instead, you could use one of the several ways to pass back a value in the Bash FAQ. Most of them aren't so great, unfortunately. You may just be stuck checking for errors after each function call (-e has a lot of problems). Either that, or switch to Perl.

Bash – Wait for key in shell script that may get piped to /bin/bash

This is really easy, actually, First, you need to set aside your stdin in some remembered descriptor:

exec 9<&0

There. You've made a copy. Now, let's pipe our commands at our shell.

echo 'echo foo; read <&9; echo bar' | bash

...well, that was easy. Of course, we're not really done yet. We should clean up.

exec 9<&-

Ok, now we're done.

But we can avoid the cleanup if we just group our commands a little...

{ echo 'echo foo; read <&9; echo bar' | bash; } 9<&0

The descriptor only survives as long as its assigned compound command does in that case.