Trouble with simple bash script to append crontab file

Question

I have a simple script that is not working as expected:

#!/bin/bash
CRONFILE="/tmp/temp_cron"
crontab -l > "$CRONFILE" 
grep "* * * * * /usr/local/bin/temp_cpu_gmetric.sh" /tmp/temp_cron
CRONCONT=`grep "* * * * * /usr/local/bin/temp_cpu_gmetric.sh" /tmp/temp_cron`
echo $CRONCONT

My crontab consists of one line, which is * * * * * /usr/local/bin/temp_cpu_gmetric.sh -- exactly the thing being grep'd for. The first instance of grep returns one instance of this character string, as expected.

However, the echo $CRONCONT instance returns with * * * * * replaced by a whole bunch of stuff. This includes the contents of the directory from which the script is run, but also many other things that I don't immediately know the location of.

If I remove * * * * * from my cronfile, the problem goes away, but I can't figure out why it shouldn't work with the * * * * * present.

Answer 1

Basically one problem is that * is a meta-character for grep . If you want to search for * you should quote it like \\* . To see why your pattern had worked out, see: this comment by chepner .

Or replace the grep command with fgrep (search for exact string.

The other problem is, that * is a meta-character for shell expansion, so you should do echo "${YOURVARIABLE}" .