Linux Desktop Hacks

226

|

Chapter 9, Administration and Automation

#73 Don’t Let Elvis Leave the Building

HACK

#!/bin/bash

# start up xcompmanager with drop shadows and fade effects

instances=`ps ax | grep "xcompmgr -cCfF" | grep -v grep | wc -l`

if [ $instances == 0 ]; then

while true; do xcompmgr -cCfF -l 0 -t 0 -r 5 -o .6 ; done

else

exit 1

fi

The first thing the script does is check to see if the command is already run-

ning. If so, the script exits. Perhaps you forgot you already started this

script, or perhaps you started the command manually. In either case, you

don’t want to start two instances, and this portion of the script prevents

that.

Notice that the

xcompmgr command is not followed with an ampersand. That

would launch xcompmgr in the background and return control to the script.

Then the script would proceed to try to launch more instances of xcompmgr

over and over again. Trust me. That’s a bad thing.

Now save your work and make this script executable with this command:

# chmod +x /usr/local/bin/keep-xcompmgr-running

The script is a simple infinite loop. But it doesn’t just start new instances of

xcompmgr over and over again. The xcompmgr program does not return

control to the script unless it fails, so this script will get to the point where it

launches the

xcompmgr command and its arguments, and then stop running.

If xcompmgr encounters a bug that causes it to exit unexpectedly, control

returns automatically