[plug] Crontab??

[Denis Brown]

Dear Jay,

On Wed, 28 Jul 2004, Jay Warwick wrote:

> On Tue, 2004-07-27 at 20:38, James Devenish wrote:
>
> > Also, note that it might not be a good idea to attempt a "long-running"
> > cron job. If you test the above and it works, you might then choose to
> > change it to this in future:
> >
> > 00      21      *       *       fri          env DISPLAY=:0 firefox &
>

<snip>

> be run instead. This brings me to my question - on the last line above,
> what is the meaning of the '&', does it allow the job to stay open for a
> longer period?
>
The & at the end of a command line causes the command, once initiated, to
be sent "to the background" for continued execution.   The means, for
example, that you can start a long job, then log off without the job
stopping (because you logged off.)

Thus you might have an hypothetical job "calculate pi to 10,000,000
decimal places" that will probably take quite some time to complete.   If
you did

myprompt> calcpi

and then logged off, the job would collapse.   On the other hand if you
added the & character

myprompt> calcpi &

you could safely log off, log back on in a week's time and check on
progress :-)   To return a job to the foreground, type fg and the job
number.   The job number can be found by using the jobs command.

I have a feeling that man bash givs more details, alterntively consult
something like the bash howto (Linux Documentation Project) or the Linux
Admnistrator's Guide (also Lin Doc Proj)

Hope this helps,
Denis