Ubuntu – xprintidle doesn’t work in cronjob. Why

cronidle

I have lxle (Lubuntu) 12.04 installed and I spent lots of time looking for working solution to make PC shutdown after some period of idle state.

After checking many programs which haven't worked I decided to spend much time of shell script solution run by cronjob

I am stuck on 2 problems here.

xprintidle doesn't give any results (empty string) when it is run by cronjob – no matter in crontab file or shell file in those environments it just give empty string instead of number of milliseconds of idle.
Secondly it seems not simple for me to run my script from crontab for shutdown commend as a root.

Could you give me a link explaining that topic? I know only sudo as a user, but script shouldn't ask for password but just shutdown system.

Best Answer

You need to set the DISPLAY environment variable before calling it, you can try this in the virtual consoles (Ctrl-Alt-F1) since they don't have the DISPLAY variable set, they will act exactly like the cron script will act.

DISPLAY=:0 xprintidle

export DISPLAY=:0
xprintidle

either should work.

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Ubuntu – Cronjob didn’t work

Make sure you are creating your cronjob using:

crontab -e

What ever user you are logged in as when you run the above command will be the user that the cronjob is executed as. If you want your cronjob run as root, you will need to be logged in as root or use the sudo command:

sudo crontab -e

If you create your job using the above command, that "root" part will break things. Your job should look like this:

  * * * * * /bin/bash /home/alan/Desktop/clientscript.sh > /home/alan/Desktop/alan.txt

Always use absolute paths in cronjobs otherwise they could break.

As noted by PerlDuck:

When the above is a cronjob in some /etc/cron.d/ file, then the root part is mandatory. But only there, as you correctly point out. cronjobs below /etc/cron.d are so called system cronjobs. The syntax is almost the same, except you must state the user as which the job is to be run in an additional column after the time specification. And of course you must be root to create files in that directory – PerlDuck

So, if you are manually creating a cron file in /etc/cron.d then the original cron job will be correct:

  * * * * * root /bin/bash /home/alan/Desktop/clientscript.sh > /home/alan/Desktop/alan.txt

IMHO, creating cronjobs with crontab -e is much easier.

Finally, you can see any output from your cronjobs by running:

 grep CRON /var/log/syslog

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