Linux command to check if a shell script is running or not

Check this

ps aux | grep "aa.sh"

Adding to the answers above -

To use in a script, use the following :-

result=`ps aux | grep -i "myscript.sh" | grep -v "grep" | wc -l`
if [ $result -ge 1 ]
   then
        echo "script is running"
   else
        echo "script is not running"
fi

The simplest and efficient solution is :

pgrep -fl aa.sh