Check if a Port is in Use or a Service is Running

#!/bin/bash

# Configuration
CHECK_PORT=80 # Port number to check
CHECK_SERVICE_KEYWORD="nginx" # Keyword to search in process list (e.g., "apache2", "node", "php-fpm")

# --- Functions ---
log_message() {
    echo "[$(date +'%Y-%m-%d %H:%M:%S')] $1"
}

check_port_status() {
    PORT=$1
    # Using ss (socket statistics) is more modern and often faster than netstat
    # -t: TCP, -l: listening, -n: numeric ports, -p: show process
    if ss -tlnp | grep -q ":$PORT\b"; then
        log_message "Port $PORT is OPEN and listening."
        ss -tlnp | grep ":$PORT\b"
        return 0 # Port is in use
    else
        log_message "Port $PORT is CLOSED or not listening."
        return 1 # Port is not in use
    fi
}

check_service_status() {
    KEYWORD=$1
    # pgrep finds processes by name or other attributes
    if pgrep -f "$KEYWORD" > /dev/null; then
        log_message "Service/Process matching '$KEYWORD' is RUNNING."
        pgrep -fla "$KEYWORD" # Show full details
        return 0 # Service is running
    else
        log_message "Service/Process matching '$KEYWORD' is NOT running."
        return 1 # Service is not running
    fi
}

# --- Main Script ---
log_message "Starting system checks..."

log_message "
--- Checking Port $CHECK_PORT ---"
check_port_status "$CHECK_PORT"
PORT_STATUS=$?

log_message "
--- Checking Service '$CHECK_SERVICE_KEYWORD' ---"
check_service_status "$CHECK_SERVICE_KEYWORD"
SERVICE_STATUS=$?

log_message "
--- Summary ---"
if [ $PORT_STATUS -eq 0 ]; then
    log_message "Port $CHECK_PORT: IN USE"
else
    log_message "Port $CHECK_PORT: NOT IN USE"
fi

if [ $SERVICE_STATUS -eq 0 ]; then
    log_message "Service '$CHECK_SERVICE_KEYWORD': RUNNING"
else
    log_message "Service '$CHECK_SERVICE_KEYWORD': NOT RUNNING"
fi

log_message "Finished system checks."