Monitor Disk Space Usage with Threshold Alert

#!/bin/bash

# Configuration
THRESHOLD=85 # Percentage (e.g., 85 for 85%)
CHECK_PATH="/"
EMAIL_RECIPIENT="[email protected]"
EMAIL_SUBJECT="CRITICAL: Disk Space Alert on $(hostname)"

# Function to send email (requires 'mail' command or similar setup)
send_alert_email() {
  local subject="$1"
  local message="$2"
  echo -e "$message" | mail -s "$subject" "$EMAIL_RECIPIENT" || {
    echo "Error: Failed to send email alert." >&2
  }
}

# Get disk usage percentage for the specified path
# Using 'df -h' for human-readable, then 'awk' to get the percentage of the specific mount point
# The regex '[0-9]+%' handles different formatting of 'df' output for the percentage column
USED_PERCENT=$(df -h "$CHECK_PATH" | awk 'NR==2 {print $5}' | sed 's/%//g')

# Validate if USED_PERCENT is a number
if ! [[ "$USED_PERCENT" =~ ^[0-9]+$ ]]; then
  echo "Error: Could not retrieve disk usage percentage for '$CHECK_PATH'." >&2
  exit 1
fi

echo "Current disk usage for $CHECK_PATH: $USED_PERCENT%"

# Check if usage exceeds the threshold
if (( USED_PERCENT >= THRESHOLD )); then
  ALERT_MESSAGE="Disk space usage on $(hostname) for $CHECK_PATH is at ${USED_PERCENT}% which exceeds the ${THRESHOLD}% threshold.
Please take action immediately."
  echo "$ALERT_MESSAGE"
  send_alert_email "$EMAIL_SUBJECT" "$ALERT_MESSAGE"
  exit 1 # Exit with error code to indicate an issue
else
  echo "Disk space usage for $CHECK_PATH is healthy (${USED_PERCENT}% < ${THRESHOLD}%)."
  exit 0 # Exit successfully
fi