How-to for crontab

[henriquemaia]

KDE has a program called KCron which does the trick, but I don't know if there's anything like it for Gnome.

Thanks for your reply, but that is not what I meant. I do not need a GUI tool for crontab or to create cron jobs (there are also a few for gnome), but I need cron to run GUI applications, like a music player or whatever. Thanks, anyway.

[evs]

Oh ok, sorry I can't help you with that. But I would be interested to find out how to do that as well.

[v0xel]

Would someone be interested in writing "Anacron HowTo", so we can have complete scheduling howto for Ubuntu?

[xtacocorex]

It didn't occur to me to use the export EDITOR=vi to get crontab -e to use vi. Must have been a brain fart when making my crons, since I have never done them until recently.

Thanks for the info.

[henriquemaia]

First, an explanation: this was meant to be a separate howto, but for some reason unknown to me, my thread didn't showed up.

To learn more about crontab, please refer to the parent post of this thread.

My motivation to find this out was because there are several radio shows I really like and I was always missing them. As such, I needed something to start amarok playing the chosen radio station at specific times. Probably this could be achieved through a more elegant solution, but this serves its purposes. Also, I knew that by learning how to do this, I could use it for many other things.

To accomplish this, you have to edit your crontab:

crontab -e

you can also use a nicer GUI tool to edit crontab, like Gnome Schedule (not in the repositories) or KCron (available on the repositories).

If you use a GUI tool, please adapt the instructions accordingly. I will explain this using as basis the default crontab editor.

To run a GUI command on cron, you'll have to tell cron what display the program should use. For that you use:

export DISPLAY=:0

:0 is the default. If you like the program to run on other display, please change the number accordingly (e.g. :1, :2, etc).

So, you add to what is explained here:

01 04 * * * /usr/bin/somedirectory/somecommand

the export variable, like this:

01 04 * * * export DISPLAY=:0 && /usr/bin/somedirectory/somecommand

So, in my case, as I want amarok to play Antena2 (radio station) at a specific time, I use:

30 16 * * 7     export DISPLAY=:0 && amarok mms://rdp.oninet.pt/antena2

This will make amarok start the Antena2 url every Sunday, at 16:30. But I want also to shut up amarok after the show is finished. So, I use:

0 17 * * 7     export DISPLAY=:0 && amarok -s

This will shut up amarok at 17:00 every Sunday.

You can use this export trick to the limits of your imagination with every kind of application you want.

Another example that occurs me is for file sharing and when your greedy ISPs only allows you a low monthly download limit, but have some kind of free download period (normally very late at night - this is the case of my ISP 8)). As such, I need to start nicotine (soulseek network application) only during that free period (3AM - 9AM). So, I use:

0 3 * * * export DISPLAY=:0 && nicotine

that will start nicotine everyday at 3AM. To shut it down, I use:

0 9 * * * killall nicotine

This will shut it down at 9AM.

Hope this helps some of you.

ps: I posted this here as it is related with the subject matter and to answer evs.

ps2: If one of the admins gets to see this, please find out what happened to my thread. I'm just wondering, because my browser looks kind of overbuggy lately (too many extensions ) and I don't even know if it was sent in the first place. Thanks a lot.

[shane2peru]

very informative, and nice howto on crontab's. Thanks.

30 23 05 * * tar cvpzf /home/shane/storage/homebackup.tgz --exclude=/Portable --exclude=/storage 
--exclude=/Pictures

Here is a simple backup crontab that I have added to mine. My question is how can I get this to do this for root, as root? Thanks. Or do I need to add this here:

crontab -u root -e

and then add my backup for my file system? Thanks.

Shane

[NobodySpecial]

shane2peru - I believe you log in as the root user, then set the crontab.

Or better yet, use the "su" command.

First, set a password for root:

sudo passwd root

Then become root:

su

Then issue your crontab commands as per above tutorial.

[shane2peru]

Oh, my bad, the real command I was using is:

sudo crontab -u root -e

Also I did get the logs to work. Unfortunately, there was some problem with my tar, and I tried to restore a backup file, and very much messed things up so I had to re-install.

Shane

[herbster]

How could I get cron to run weighttraninglog.xls every night at 11pm? I don't know what the command is to run an .xls file, which is associated with OpenOffice for me and works fine of course, just don't know the terminal command. Anyone ??

[pidgas]

To open an xls file on a schedule just requires a synthesis of what's been put in this thread so far. The only piece of missing info is the command for openoffice calc (like excel). That command is "oocalc". To open a file using oocalc from the command-line is just

oocalc /path/to/file.xls

To get a job to do this on a schedule just create a cron job to perform following command on the schedule you wish. The command(s) you need is/are:

export DISPLAY=:0 && oocalc /path/to/file.xls

This cron job line should do what you want to do (adjust path to your excel file as necessary)

00 23 * * * export DISPLAY=:0 && /usr/bin/oocalc /path/to/weigttraininglog.xls

Hope that helps!