Implement Robust Error Handling and Logging in Bash

#!/bin/bash

# --- Configuration ---
LOG_FILE="/tmp/myscript.log"
DATE_FORMAT="+%Y-%m-%d %H:%M:%S"

# --- Logging Functions ---
log() {
  echo "$(date "$DATE_FORMAT") [INFO] $1" | tee -a "$LOG_FILE"
}

warn() {
  echo "$(date "$DATE_FORMAT") [WARN] $1" | tee -a "$LOG_FILE" >&2
}

error() {
  echo "$(date "$DATE_FORMAT") [ERROR] $1" | tee -a "$LOG_FILE" >&2
}

# --- Error Handling ---
_cleanup() {
  log "Script finished or terminated. Cleaning up..."
  # Add any cleanup commands here (e.g., remove temp files)
  # rm -f /tmp/mytempfile.txt
}

_error_exit() {
  local last_command="$BASH_COMMAND"
  local exit_code=$?
  error "Last command '${last_command}' failed with exit code ${exit_code} on line ${BASH_LINENO[0]}."
  _cleanup
  exit "${exit_code}"
}

# Exit immediately if a command exits with a non-zero status.
set -e

# Execute _error_exit function on EXIT signal (normal exit or error)
# trap '_error_exit' EXIT # This will call _error_exit on any exit, success or failure.
# A more common approach:
trap '_error_exit' ERR

# Execute _cleanup function on SIGHUP, SIGINT, SIGQUIT, SIGTERM
trap '_cleanup' SIGHUP SIGINT SIGQUIT SIGTERM

# --- Main Script Logic ---
log "Script started."

# Example commands (some might fail)
echo "Performing task 1..."
sleep 1
log "Task 1 complete."

echo "Attempting a command that might fail (e.g., trying to remove a non-existent dir with -r)..."
rm -r non_existent_directory_123 || warn "Could not remove non_existent_directory_123 as expected (it didn't exist)."

echo "Attempting a command that WILL fail and trigger error trap..."
# This command is expected to fail and exit due to 'set -e'
# The 'trap ERR' will then catch it.
cp /non/existent/source /tmp/destination_file

log "This line will not be reached if the above 'cp' command fails."

# If the script reaches here, it means no critical error occurred.
log "Script completed successfully."
_cleanup # Manual call if trap EXIT is not used and script ends successfully