Kernel#exit!

exit!(status = false)

Returns: Never returns · Updated March 13, 2026 · Kernel Methods

process exit termination status

The exit! method terminates the Ruby process immediately without running any cleanup code. Unlike exit, it does not run at_exit handlers or ensure finalizers.

Basic Usage

# Exit with default code 1
exit!

# Exit with specific code
exit!(0)  # Success
exit!(1)  # Error
exit!(2)  # Another error code

How It Differs from exit

# exit - runs at_exit handlers
at_exit { puts "Cleaning up..." }
exit
# Output: Cleaning up...

# exit! - immediate termination
at_exit { puts "Cleaning up..." }
exit!
# No output - exits immediately

Practical Examples

Fork Safety

# In parent process after fork
if fork.nil?
  # Child process
  # Exit immediately without running parent's at_exit
  exit!
end

Timeout Handling

# Kill process after timeout
begin
  Timeout.timeout(5) do
    long_running_task
  end
rescue Timeout::Error
  # Force exit without cleanup
  exit!(1)
end

Signal Handling

trap(:KILL) { exit! }  # Cannot trap KILL anyway
trap(:TERM) { exit!(1) }  # Force TERM to exit immediately

Testing

# Exit child in tests without running other code
def run_test_case(test)
  fork do
    begin
      test.run
    rescue => e
      puts "Test failed: #{e}"
      exit!(1)
    end
  end
end

Exit Codes

exit!(0)   # Success
exit!(1)   # General error
exit!(2)   # Misuse of command
exit!(126) # Command not executable
exit!(127) # Command not found
exit!(128) # Invalid exit argument

When to Use exit!

After fork to avoid double at_exit runs
When you need guaranteed immediate termination
In signal handlers where cleanup isn’t desired
Performance-critical code where cleanup overhead matters

When NOT to Use exit!

Normal application termination (use exit)
When you need cleanup code to run
In daemons that need to flush buffers
When at_exit handlers contain important cleanup