Kill process running on a port

kill_port.sh

#!/bin/bash
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
NC='\033[0m'

if [ $# -eq 0 ] ; then
	echo -e "${RED}Error: No port given${NC}"
	exit 1
fi

if ! [[ $1 =~ ^[0-9]+$ ]] ; then
	echo -e "${RED}Error: Port is not a number${NC}"
	exit 1
fi

PID="$(lsof -i :$1 -t)"

if [[ -z "${PID// }" ]] ; then
	echo -e "No process running on port ${YELLOW}${1}${NC}"
else
	echo -e "Process with pid ${GREEN}${PID}${NC} running on port ${YELLOW}${1}${NC}"
	echo -e "Killing process…"
	kill -- -$(ps -o pgid= $PID | grep -o [0-9]*)
fi