SHELL

start a service in bash if stopped

#!/bin/bash
SERVICE="nginx"
if pgrep -x "$SERVICE" >/dev/null
then
    echo "$SERVICE is running"
else
    echo "$SERVICE stopped"
    # uncomment to start nginx if stopped
    # systemctl start nginx
    # mail  
fi

bash only start a service if not running

#!/bin/bash
service=replace_me_with_a_valid_service

if (( $(ps -ef | grep -v grep | grep $service | wc -l) > 0 ))
then
echo "$service is running!!!"
else
/etc/init.d/$service start
fi