Find available ports in bash

getUnusedPorts.sh

#!/usr/bin/env bash

# Get available ports to be used by webpack-dev-server and mock server.

IP=127.0.0.1
start_port=8000
end_port=8100

scanner() {
  local port="$start_port"
  local avail_ports=$(while [[ ! "$port" -gt "$end_port" ]]; do
    lsof -i ":$port" > /dev/null 2>&1 || echo "$port"
    ((port++))
  done)
  echo "$avail_ports"
  return $?
}

scanner

exit 0