How to check process is running from its pid number, in bash

13 March 2017 
#!/bin/sh

PID=`cat /var/www/etecnic/shared/tmp/pids/http_server.pid`
RESULT=`ps aux | grep http_server | grep $PID`

if [ "${RESULT:-null}" = null ]; then
    echo ">>>> :( OCPP SERVER NOT RUNNING !!!"
else
    echo ">>>> OK - OCPP SERVER RUNNING"
fi