I have new to scripts .. I want to monitor service on the server - we have two scripts 1 - for checking service is running or not (checking.sh) 2 - start the service (start.sh)
I would like to merge two scripts into single (monitor.sh) and schedule/ cron it. how do I run second script based on first script result IF first script result is 0 need to start the service (second script need to run) ,if first script result is 1 second script no need to run and exit main script.
This is what exit codes are for. So, for your monitor script, we could do something like:
#!/bin/bash
# monitor.sh -- checks if a Thing is doing its Thing
if [[ -r /var/run/myjob.pid ]]; then
if kill -0 $( cat /var/run/myjob.pid ); then
exit 0 # The process is alive, job is presumably running
else
exit 1 # Well, we had a PID file, but it was orphaned.
fi
else
exit 2 # no PID file, job presumably not running
fi
We use a different exit code for each state we wish to handle. Then, for our service checker:
#!/bin/bash
# check.sh -- Checks to see if Thing is Thinging and, if not, start it
if ! /path/to/monitor.sh; then
/path/to/start.sh
fi
And now, the script that runs the job:
#!/bin/bash
# start.sh - do a Thing
if [[ -r /var/run/myjob.pid ]]; then
echo "A Thing is already being done!" 1>&2
exit 1
else
echo $$ > /var/run/myjob.pid
trap 'rm /var/run/myjob.pid' EXIT
do_Thing_related_things
fi
