#!/bin/bash
# Usage: "Linux - RAM usage monitor.sh 80 95"
# 
# Description:
#   This script is used from inside of Tactical RMM instances to check the RAM usage. 
#   This script should be deployed as a check script.
#
# Options:
#   Arg1 - Warning limit
#   Arg2 - Error limit
#
# Author: D. de Kooker (info@dcomputers.nl)
# Sources: https://www.activexperts.com/support/network-monitor/online/linux/
# Changelog :
#   27-06-2022 - Initial script from source, tweaked for my environment
#   16-09-2023 - Changed the way the RAM performance is monitored to TOP, because of false positives in alerting.

# Default values for WARNING and ERROR limits (in percentage)
WARNING_LIMIT=85
ERROR_LIMIT=95

# Check for command line arguments
if [ $# -eq 2 ]; then
  WARNING_LIMIT=$1
  ERROR_LIMIT=$2
fi

# Function to check RAM usage
check_ram_usage() {
  RAM_TOTAL=$(free -m | awk '/^Mem:/ {print $2}')
  RAM_USED=$(free -m | awk '/^Mem:/ {print $3}')
  RAM_USAGE_PERCENTAGE=$(echo "scale=2; $RAM_USED / $RAM_TOTAL * 100" | bc)
  
  if [ "$(echo "$RAM_USAGE_PERCENTAGE >= $ERROR_LIMIT" | bc -l)" -eq 1 ]; then
    echo "ERROR: RAM usage is ${RAM_USAGE_PERCENTAGE}% (>= ${ERROR_LIMIT}%)"
    exit 1
  elif [ "$(echo "$RAM_USAGE_PERCENTAGE >= $WARNING_LIMIT" | bc -l)" -eq 1 ]; then
    echo "WARNING: RAM usage is ${RAM_USAGE_PERCENTAGE}% (>= ${WARNING_LIMIT}%)"
    exit 2
  else
    echo "OK: RAM usage is ${RAM_USAGE_PERCENTAGE}%"
    exit 0
  fi
}

check_ram_usage