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Old 03-31-2008, 04:18 PM   #1
Registered: Oct 2006
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single command in shell script not working

I have a shell script that is giving me a headache. It logs into a device runs a command and copies the output to a file. then an if grep "$sometrigger" test puts the network name of the device into a file. I then run "sort -u" on the file containing the list of device names that tested positive and start the process over with the list that tested positive the first pass to help eliminate false positives. I run "sort -u" on the list created by the second pass and put that into my final output file. I put this all together and tested in and it worked, then I added it to roots crontab to run every afternoon (I know I know it shouldn't be done as root)

the issue I am having is that neither "sort -u" command ever seems to work when run by cron. I checked the shebang and it is bash, the same shell I wrote and tested the script in. I ran "which sort" as both root and the user I wrote and tested as and the path is the same. I tried using the absolute path to sort even though which indicated it was using the same utility. I tried sorting the file and then piping to uniq separately, uniq didn't work because the file never sorted.

can someone please point me in the right direction so I can figure out why this script refuses to sort any of the files it has created?
Old 03-31-2008, 04:23 PM   #2
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Originally Posted by farkus888
the issue I am having is that neither "sort -u" command ever seems to work when run by cron.
The most common issues with cronjobs are related to its limited PATH.

So, either build PATH at the start of your script, or use the FQ path to the sort program.


edit: I missed this at first read:
Originally Posted by farkus888
I tried using the absolute path to sort...
Are you sure you tried that? If so, next I'd turn on trace (set -x) near the start of the script to see what's happening. You'll get stdout/stderr from the cronjob sent to the user's mail.

Last edited by anomie; 03-31-2008 at 04:25 PM.
Old 03-31-2008, 04:27 PM   #3
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Scripts run from cron do not have any system wide environment variables; such as PATH. The variables needed must be explicitly defined within your script. However, you can use the absolute path name to each of the executables executed within your cronjob, but I find it easier to echo $PATH from the shell I am testing the script in and include this within the script. ie,

# echo $PATH

#! /bin/sh
export PATH=/usr/sbin:/usr/ccs/bin


Last edited by prad77; 04-17-2008 at 03:32 AM.
Old 03-31-2008, 04:28 PM   #4
Registered: Oct 2006
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I have tried using the absolute pathname to the sort utility that I want used. I have all the cron jobs on this server set up to send all of their stdout and stderr to /dev/null to keep things cleaned up. I am in the process of running the script by hand as both accounts to see if any of the output differs right now. unfortunately its a time consuming process because of waiting for the output from 800+ devices.

Last edited by farkus888; 03-31-2008 at 04:45 PM.
Old 04-01-2008, 12:11 AM   #5
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Perhaps you can use nice to higher the sleeping rate of sort. Do 'man nice' for more info.. Also use absolute pathnames please.

# nice -n 4 /path/sort -u
Old 04-01-2008, 01:31 PM   #6
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I have not taken the absolute pathnames for each call of sort out of the script yet because I know they can't hurt. I did get an error running the script by hand last night that I am looking into, I will update with the fix if I find one.


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