Implement Robust Script Cleanup with Trap

#!/bin/bash

# --- Configuration and temporary resource setup ---
# Create a unique temporary directory for this script instance
TMP_DIR=$(mktemp -d -t myapp-XXXXXXXX)
TMP_FILE="$TMP_DIR/temp_data.txt"
BACKGROUND_PID=""

# --- Cleanup function ---
# This function will be called on script exit or interruption
cleanup() {
  echo "
--- Running cleanup function ---"
  # Remove temporary directory and its contents
  if [ -d "$TMP_DIR" ]; then
    echo "Removing temporary directory: $TMP_DIR"
    rm -rf "$TMP_DIR"
  fi

  # Kill any background processes started by this script
  if [ -n "$BACKGROUND_PID" ]; then
    echo "Killing background process with PID: $BACKGROUND_PID"
    kill "$BACKGROUND_PID" 2>/dev/null # Suppress error if process already dead
  fi
  echo "Cleanup complete."
}

# --- Set up traps ---
# The cleanup function will be executed when the script receives:
#   EXIT:   Upon normal or abnormal termination
#   INT:    Interrupt signal (e.g., Ctrl+C)
#   TERM:   Terminate signal (e.g., `kill <pid>`)
trap cleanup EXIT INT TERM

echo "Script started. Temporary directory created: $TMP_DIR"

# --- Simulate script work ---
echo "Working with temporary file: $TMP_FILE"
echo "Hello World" > "$TMP_FILE"
cat "$TMP_FILE"

# Simulate a background process that needs to be cleaned up
( while true; do echo "Background process running..."; sleep 2; done ) & # Run in background
BACKGROUND_PID=$!
echo "Background process started with PID: $BACKGROUND_PID"

# Simulate a long-running task. Try pressing Ctrl+C during this sleep.
echo "
Sleeping for 10 seconds (try Ctrl+C to test cleanup)...
(You should see 'Cleaning up...' messages after interruption)"
sleep 10

echo "
Script finished successfully. (Cleanup will still run on EXIT)"