Script with lsof works well on shell not on cron

Question

I have a small script do count open files on Linux an save results into a flat file. I intend to run it on Cron every minute to gather results later. Script follows:

/bin/echo "Timestamp: ` date +"%m-%d-%y %T"` Files: `lsof | grep app | wc -l`"

And the crontab is this:

*/1 * * * * /usr/local/monitor/appmon.sh >> /usr/local/monitor/app_stat.txt

If I run from shell ./script.sh it works well and outputs as:

Timestamp: 01-31-13 09:33:59 Files: 57

But on the Cron output is:

Timestamp: 01-31-13 09:33:59 Files: 0

Not sure if any permissions are needed or similar. I have tried with sudo on lsof without luck as well.

Any hints?

Answer 1

from your working cmd-line, do

which lsof
which grep
which wc
which date

Take the full paths for each of these commands and add them into your shell script, producing something like

/bin/echo "Timestamp: `/bin/date +"%m-%d-%y %T"` Files: `/usr/sbin/lsof | /bin/grep app | /bin/wc -l`"

OR you can set a PATH var to include the missing values in your script, i.e.

 PATH=/usr/sbin:${PATH}

Also unless you expect your script to be run from a true Bourne Shell environment, join the early 90's and use the form $( cmd ... ) for cmd-substitution, rather than backticks. The Ksh 93 book, published in 1995 remarks that backticks for command substitution are deprecated ;-)

IHTH