prevent that two same scripts run concurrently

concurrently.sh

#!/bin/sh

PIDFILE=/tmp/update_index.pid

if [ -e $PIDFILE ]
then
	PID=$(cat $PIDFILE)

	PSCNT=$(ps -p $PID | grep -v CMD | wc -l)

	if [ $PSCNT -le 0 ]
	then
		echo "Invalid PID file"
		rm -rf $PIDFILE
	else
		PROCINFO=$(ps --ppid $PID | grep -v CMD)
		echo "Another process is running.."
		echo $PROCINFO
		exit
	fi
fi

echo $$ > $PIDFILE

/usr/bin/python  /var/www/SearchSource/Market/UpdateIndex.py

rm -rf $PIDFILE