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Old 11-18-2005, 10:44 AM   #1
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Registered: May 2004
Location: Glasgow, Scotland
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cron spawning extra crond - script fails


I have searched for cron in these forums and can't seem to finds anyone who has a similar problem. Hope you can help!

I have a script called metadata.refresh that I would like to execute every five minutes. If I execute this script as root, it runs successfully, copying the webpage to local files (then cleaning up) - basically doing all it should:

cd /root/downloads/SDSS
rm -f sdss-sites.*
rm -f sdss-trust.*
wget (website here)
wget (website here)
/usr/bin/siterefresh --out sdss-sites.xml --url (webpage)
/usr/bin/siterefresh --out sdss-trust.xml --url (webpage)
rm sdss-sites.xml
rm sdss-trust.xml
When setting up this as a cron job, I made the following crontab:

0,5,10,15,20,25,30,35,40,45,50,55 * * * * /usr/local/metadata.refresh
When the cron job executes I get the following on ps -ef (ignorning irrelevant procs):

root     3345      1  crond
root    21654  3345 CROND
root    21655 21654 /bin/sh /usr/local/metadata.refresh
root    21656 21655 wget (1st webpage in script)
root    21657 21654 /usr/sbin/sendmail -FCronDaemon -i -odi -oem root
Why is this extra CROND process spawning (i already have a cron daemon)? I thought it was the mail part messing it up so I put MAILTO="" at the top of my crontab, then I get the same output above except the sendmail line is missing. I have tried piping the output ( /dev/null 2>&1) but this doesn nothing. I have also put an extra empty line at the end of the crontab.

I don't understand why the script runs perfectly when executed normally, but the cronjob can't complete it.

Any ideas?

Much obliged
Old 11-19-2005, 06:29 AM   #2
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Registered: May 2005
Location: Atlanta Georgia USA
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root 3345 1 crond
root 21654 3345 CROND
Notice the CROND with PID (Process ID) 21654 has PPID (Parent Process ID) of 3345 and 3345 is the PID of crond. This means crond itself is spawning this so its not likely a problem. (Note: Case is signicant in UNIX/Linux so crond and CROND are NOT the same thing.)

The problem is most likely environmental. When a script is run from the command line it inherits the user's environment (/etc/profile, /etc/bashrc, $HOME/.profile, $HOME/.bashrc and perhaps others) so it knows full paths to commands. However when it runs from cron it does NOT inherit an environment so doesn't have full paths. Therefore one has to setup the environment in the script itself or just hard code the paths.

Instead of just rm... do /usr/bin/rm... (assuming rm is in /usr/bin - typing "which rm" will tell you where it is - I'm not in front of my Linux box at the moment).

Do same for wget. You don't need to for cd as it is an internal command of the shell.
Old 11-21-2005, 04:29 AM   #3
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Registered: May 2004
Location: Glasgow, Scotland
Posts: 4

Original Poster
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Thanks for your help! Problem solved. Script now looks like this:


export http_proxy=(our proxy)
export HTTP_PROXY=$http_proxy
cd /root/downloads/SDSS
/bin/rm -f sdss-sites.*
/bin/rm -f sdss-trust.*
/usr/bin/wget (website here)
/usr/bin/wget (website here)
/usr/bin/siterefresh --out sdss-sites.xml --url (webpage)
/usr/bin/siterefresh --out sdss-trust.xml --url (webpage)
/bin/rm sdss-sites.xml
/bin/rm sdss-trust.xml
I put the full paths in and had to define my proxy, but after that it works a treat.



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