[Sussex] Regular scheduled jobs?

[John D.]

On Fri, 2005-04-01 at 11:50 +0100, Richie Jarvis wrote:
> John D. wrote:
> > I suspect that I was getting rather lost, because it went off into
> > technospeak at quite an early stage - and not being able to find
> > anything on the system that remotely resembled what the howto was
> > talking about, threw me somewhat!
> Hi John,
> 
> Firstly, forget about anacron and vixie-cron - they are not what you 
> want to achieve, they simply execute missed jobs when the machine wasn't 
> turned on, or cron wasn't running.
> 
> For a first cut in cron land, try this:
> 
> The command you want is crontab.  It has 2 (important) options: -l and -e
> 
> crontab -l will list the contents of that users crontab.  Cron maintains 
> a different schedule list for each user, and therefore what you see in 
> the crontab -l listing for one user will be different to another.  Here 
> is one of my machines root user crontab:
> 
> Example of crontab -l:
> 
> -bash-2.05b# crontab -l
> # DO NOT EDIT THIS FILE - edit the master and reinstall.
> # (/tmp/crontab.4593 installed on Tue Oct 26 12:56:21 2004)
> # (Cron version -- $Id: crontab.c,v 2.13 1994/01/17 03:20:37 vixie Exp $)
> 00 20 * * * /data/dbbackups/mysql/windward-backup-script.sh
> 
> The above crontab shows 1 job - the other lines prefixed by # are 
> comments.
> 
> crontab -e simply starts your chosen editor (usually vi) in the crontab 
> file, which allows you to enter new jobs and modify or delete existing 
> jobs.  Each job must be on one line in the crontab file.
> 
> There are 6 fields in the cron job shown above, separated by a space 
> character:
> 
> position 	field          	allowed values
> --------	-----          	--------------
> 1		minute         	0-59
> 2		hour           	0-23
> 3		day of month   	1-31
> 4		month          	1-12 (or names, see below)
> 5		day of week    	0-7 (0 or 7 is Sun, or use names)
> 6		command	 	the command or script you wish to run
> 
> So, to make cron dump the output from dmesg to file at at 03:35 on every 
> tuesday, I would enter the following into the crontab file:
> 
> 35 03 * * 2 dmesg > /var/log/dmesgoutput
> 
> The * values mean that the day of month and month values are to be ignored.
> 
> To confirm that cron has done its job, check the /var/log/cron file (on 
> FC3 systems - may be different on Gentoo) This file shows an entry each 
> time cron executes a job, or crontab is used to list or edit the job list.
> 
> Example of /var/log/cron from an FC3 system:
> 
> Apr  1 11:30:00 windward CROND[3563]: (apache) CMD (php 
> /var/www/html/cacti/cmd.php > /var/log/cacti.log 2> /dev/null)
> Apr  1 11:30:00 windward CROND[3564]: (root) CMD (/usr/lib/sa/sa1 1 1)
> Apr  1 11:35:00 windward CROND[5309]: (apache) CMD (php 
> /var/www/html/cacti/cmd.php > /var/log/cacti.log 2> /dev/null)
> Apr  1 11:35:12 windward crontab[5405]: (cc) LIST (cc)
> Apr  1 11:35:19 windward crontab[5455]: (richie) LIST (richie)
> Apr  1 11:35:27 windward crontab[5544]: (root) LIST (root)
> Apr  1 11:40:00 windward CROND[7086]: (apache) CMD (php 
> /var/www/html/cacti/cmd.php > /var/log/cacti.log 2> /dev/null)
> Apr  1 11:40:00 windward CROND[7087]: (root) CMD (/usr/lib/sa/sa1 1 1)
> 
> Anyway, that is a quick intro to cron.  You can do other funky things, 
> like making cron execute a job every X minutes, or hours.  And also you 
> can make cron mail different users, or discard the output.  The 
> possibilities are (almost) endless.
> 
> The next part of your task once you have got to grips with cron (from 
> what you said to me last night) is to find a command to dump a colour 
> print job to a printer.  I must admit I am not sure what to advise on 
> that score.  Personally, I would probably make test page, and then write 
> the postscript to file, and then write that file directly to the printer 
> port - whether that will work or not, I don't know (never tried it!), 
> but that would be my first port of call.

Thanks for that Richie, I'm not sure if you saw the post that replied to
one from Thomas, but it wasn't until I'd actually emerged anacron (and
vixie-cron, which was a dependency of anacron), that I got anything like
a reply from the command man crontab. I'm not sure why that might have
been, because there did seem to be some sort of cron installed already
(as far as I could tell).

I'm gonna check out your post fully later on in the week, as we're off
out to eat tonight. Plus, between sorting my fish, trying to get to the
BCF tomorrow, starting moving stuff to decorate the main bedroom, etc
etc, I suspect that if I sit down in front of the monitor for any longer
than it takes to check my e-mail I suspect i'll end up "in the
doghouse"!

Thanks for the assist thus far (ditto Thomas Adam), I suspect that I'll
have more Q's a little later in the week.

regards

John D.