Check if program is running with bash shell script? - shell

Question

This is an example of a bash script which checks for some running process (daemon or service) and does specific actions (reload, sends mail) if there is no such process running.
check_process(){
# check the args
if [ "$1" = "" ];
then
return 0
fi
#PROCESS_NUM => get the process number regarding the given thread name
PROCESS_NUM='ps -ef | grep "$1" | grep -v "grep" | wc -l'
# for degbuging...
$PROCESS_NUM
if [ $PROCESS_NUM -eq 1 ];
then
return 1
else
return 0
fi
}
# Check whether the instance of thread exists:
while [ 1 ] ; do
echo 'begin checking...'
check_process "python test_demo.py" # the thread name
CHECK_RET = $?
if [ $CHECK_RET -eq 0 ]; # none exist
then
# do something...
fi
sleep 60
done
However, it doesn't work. I got "ERROR: Garbage option." for the ps command. What's wrong with these scripts? Thanks!

Answer 1

You can achieve almost everything in PROCESS_NUM with this one-liner:
[ `pgrep $1` ] && return 1 || return 0
if you're looking for a partial match, i.e. program is named foobar and you want your $1 to be just foo you can add the -f switch to pgrep:
[[ `pgrep -f $1` ]] && return 1 || return 0
Putting it all together your script could be reworked like this:
#!/bin/bash
check_process() {
echo "$ts: checking $1"
[ "$1" = "" ] && return 0
[ `pgrep -n $1` ] && return 1 || return 0
}
while [ 1 ]; do
# timestamp
ts=`date +%T`
echo "$ts: begin checking..."
check_process "dropbox"
[ $? -eq 0 ] && echo "$ts: not running, restarting..." && `dropbox start -i > /dev/null`
sleep 5
done
Running it would look like this:
# SHELL #1
22:07:26: begin checking...
22:07:26: checking dropbox
22:07:31: begin checking...
22:07:31: checking dropbox
# SHELL #2
$ dropbox stop
Dropbox daemon stopped.
# SHELL #1
22:07:36: begin checking...
22:07:36: checking dropbox
22:07:36: not running, restarting...
22:07:42: begin checking...
22:07:42: checking dropbox
Hope this helps!

Answer 2

If you want to execute that command, you should probably change:
PROCESS_NUM='ps -ef | grep "$1" | grep -v "grep" | wc -l'
to:
PROCESS_NUM=$(ps -ef | grep "$1" | grep -v "grep" | wc -l)

Answer 3

PROCESS="process name shown in ps -ef"
START_OR_STOP=1 # 0 = start | 1 = stop
MAX=30
COUNT=0
until [ $COUNT -gt $MAX ] ; do
echo -ne "."
PROCESS_NUM=$(ps -ef | grep "$PROCESS" | grep -v `basename $0` | grep -v "grep" | wc -l)
if [ $PROCESS_NUM -gt 0 ]; then
#runs
RET=1
else
#stopped
RET=0
fi
if [ $RET -eq $START_OR_STOP ]; then
sleep 5 #wait...
else
if [ $START_OR_STOP -eq 1 ]; then
echo -ne " stopped"
else
echo -ne " started"
fi
echo
exit 0
fi
let COUNT=COUNT+1
done
if [ $START_OR_STOP -eq 1 ]; then
echo -ne " !!$PROCESS failed to stop!! "
else
echo -ne " !!$PROCESS failed to start!! "
fi
echo
exit 1