A port scanner in bash. No netcat / nmap is required. Might be useful when discover open ports in internal network on a Linux server.

scan_ports_with_bash.sh

#!/bin/bash

# Example of using bash with array
port_arr=(80 22 3306)
max_timeout=2 # Timeout requires coreutils (on Debian-based system)

function do_scan_port {
  # If use array like above, use the line above
  for port in "${port_arr[@]}"; do
  # Otherwise, use the port range
  # for port in $(seq 9990 10000); do
    # Check open ports
    { timeout $max_timeout bash -c "echo \"\" >/dev/tcp/$1/$port && echo \"Open port: ${1}:${port}\"" ;} 2>/dev/null
  done
}

do_scan_port google.com

# Example of using bash for IP range
# 172.16.1.3/24
#for ip in 172.16.1.{1..254}; do
#  do_scan_port $ip
#done

# 172.16.1.3/20
#for ip in 10.11.{48..63}.{1..254}; do
#  do_scan_port $ip
#done

Update time out so script wont hang.

Add & to end of line of scan command could running multiple processes scanning the host?