Assuming you have are monitoring the /var filesystem on a Solaris system then you could use:

Code:

$ df -k /var
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/dsk/c0t0d0s3     138703    65426  59407    53%    /var
$

So to extract the value you could use:

Code:

$ df -k /var | grep /var$ | awk '{ print $5 }'

Which will extract the percentage full (the fifth item in the list) avoiding picking up the fifth item in the header line.

So in a script you would so:

Code:

PERCENTFULL=`df -k /var | grep /var$ | awk '{ print $5 }'`

You can then test for a value greater than 90% you can do:

Code:

if [ ${PERCENTFULL} -gt 90 ]; then
  send_an_email
fi

Sending an email depends on what you have on your system, on Solaris I would use mailx thus:

Code:

mailx -s "Subject heading" person@domain.com < inputfile

Where you have put what you want to send in the message in inputfile.

You would then call the resulting script from cron at 8pm every night:

Code:

0 20 * * * /usr/local/bin/yourscript.sh

HTH