Bash Script - Running current or new instance of an application

Question

I added a shortcut to an application in ubuntu. Each time i press shortcut keys, a new instance of application is created. I need only one instance, what script i can use to open the existing instance of application or creates a new one if the application is not running?

Answer 1

It depends greatly on the application. The most trivial case would be the known process name which can only be run by you (that is, no stray instances on the system):

pidof applicaton || /usr/bin/application

Opening an existing application may get tricky and, again, depends on the application. I'd suggest that you take a look at alltray thingie and pay special attention to the alltray --help output.

Edit by ypnos: If you want to restrict this to the current user only, you should use pgrep instead of pidof, like this:

pgrep -u `id -u` application || application

Answer 2

You can also try a script like this:

#! /bin/bash
user=`id -un`
lock=/tmp/$user-$1-lock
if [ -e $lock ]; then
    exit #app is already running
fi

touch $lock
$@
rm $lock

If you called the script 'runner.sh', you can use it like this:

runner.sh xcalc

Is for cases where pidof doesn't work. Else go for hacker's solution, which is also more robust.