Checks the status of specified ports on a system output as columnar data including protocol, local address, process name, and PID

check_ports.sh

#!/bin/bash

# Port Checker Script
# This Bash script checks the status of specified network ports on a system.
# It utilizes the `ss` command to determine if each port is being listened to 
# and retrieves associated process information, including the protocol (Netid), 
# local address, process name, and PID. The output is formatted in a columnar 
# structure for easy reading. The script requires elevated privileges to access 
# process information.
#
# Usage:
# ./check_ports.sh <port1> <port2> ... <portN>

# Check if at least one argument (port) is provided
if [ "$#" -eq 0 ]; then
    echo "Usage: $0 <port1> <port2> ... <portN>"
    exit 1
fi

# Use sudo to execute the ss command
sudo ss -tulnp &> /dev/null
if [ $? -ne 0 ]; then
    echo "This script requires elevated privileges to check the ports."
    echo "Please run it with sudo."
    exit 1
fi

# Print header
printf "%-10s %-10s %-30s %-20s %-10s\n" "PortNum" "Netid" "LocalAddress" "ProcessName" "PID"
printf "%-10s %-10s %-30s %-20s %-10s\n" "-------" "-----" "-------------" "------------" "----"

# Sort the ports numerically and iterate over each provided port
for port in $(printf "%s\n" "$@" | sort -n); do
    # Use 'ss' to check if the port is being listened to and get the process name
    output=$(sudo ss -tulnp | grep ":$port ")

    if [ -n "$output" ]; then
        # Process multiple lines of output for the same port
        while IFS= read -r line; do
            # Extract fields
            netid=$(echo "$line" | awk '{print $1}')                    # Extract Netid (protocol)
            local_address=$(echo "$line" | awk '{print $5}')           # Extract Local Address
            process_name=$(echo "$line" | grep -oP 'users:\(\("\K[^"]+')  # Extract Process Name
            pid=$(echo "$line" | grep -oP '(?<=pid=)\d+')                # Extract PID

            # Handle empty process name case
            if [[ -z $process_name ]]; then
                process_name="<No Process>"
            fi
            
            # Handle empty PID case
            if [[ -z $pid ]]; then
                pid="<N/A>"
            fi

            # Output in columnar format
            printf "%-10s %-10s %-30s %-20s %-10s\n" "$port" "$netid" "$local_address" "$process_name" "$pid"
        done <<< "$output"
    else
        # If the port is not being listened to, print in the same format
        printf "%-10s %-10s %-30s %-20s %-10s\n" "$port" "<N/A>" "<Not Listening>" "<N/A>" "<N/A>"
    fi
done