[ILUG] Bash script - technical question

[David Pintor]

That's great information Gareth. I figured out the crontab delay last night
and fix it.
The idea of the daemon + the crontab job controlling it sounds like a good
idea... I might give it a try...

Thanks!

David



On 1 November 2010 08:35, Gareth 'bigbro' Eason <bigbro at skynet.ie> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 30/10/10 17:05, David Pintor wrote:
> > Hi,
> >
> > Thanks for your responses... :-)
> >
> > Just in case anyone's interested, I found a more or less nice way to do
> > this, using a file that stores the seconds and using both sleep and the
> > crontab...
> >
> > Basically:
> >
> > if interval >= 1 min
> >    sleep ` cat secs.txt`
> [snip]
>
>        Note that Cron does not guarantee to run things at :00 seconds, so
> if
> you are looking to run a script at accurately spaced intervals it sounds
> to me like an ideal use of a daemon (which can use sleep and a couple of
> other checks to ensure accuracy depending on the level required.)
>
>        I had what sounds like a similar to yours some time ago and I found
> that the simplest, most reliable and most accurate way of achieving this
> was to write the script as a daemon, including appropriate /etc/init.d/
> scripts in place such that it was stopped and started correctly on
> system shutdown/restart.
>
>        A quick google yields
> http://www.netzmafia.de/skripten/unix/linux-daemon-howto.html which
> appears to be a very reasonable and simple tutorial (in C.) If you have
> a script that already contains the functionality you require, remember
> you can always just call that script from within the C daemon code,
> being careful of security issues (i.e. can someone replace the shell
> script and get your daemon to them run their code as root, or similar?)
>
>        In my case I also wrote a small crontab job to make sure that the
> daemon was still running, restarting it and raising an alarm if it
> discovered the daemon process wasn't there. This made a fairly reliable
> method of definitely running some process at fairly accurate fixed time
> intervals.
>
>        Hope this helps.
>
>        Best regards,
>        -->Gar
>
>
>        Hope that helps.
>
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.10 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
>
> iEYEARECAAYFAkzOe8IACgkQK36C50PvIR8DWQCfZt24zhiXdAjB4jXihukGovei
> R6sAniYBwJQ0ehZ0do/EoscwxtwiloKA
> =QLKU
> -----END PGP SIGNATURE-----
> --
> Irish Linux Users' Group mailing list
> About this list : http://mail.linux.ie/mailman/listinfo/ilug
> Who we are : http://www.linux.ie/
> Where we are : http://www.linux.ie/map/
>