Find the next available port when starting the Rails server

rserv-func.sh

function rserv()
{
  rport=3000
  port_taken=`lsof -i tcp:${rport}`
  while [ $port_taken ]
  do  
    echo "Port ${rport} taken..."
    (( rport++ ))
    port_taken=`lsof -n -i tcp:${rport}`
  done
  echo "Port ${rport} free, starting server..."
  rails s -p ${rport}
}