trellis

Interrupt Demo

This example demonstrates how to handle Global Signals (specifically SIGINT / Ctrl+C) in Trellis.

The Problem

In many CLI applications, pressing Ctrl+C kills the process immediately, leaving resources dangling or transactions incomplete. Trellis allows you to intercept this signal and transition to a specific node (e.g., a confirmation screen or cleanup routine) instead of crashing.

The Solution

The on_signal property in the start.md node defines the handler:

on_signal:
  interrupt: confirm_exit

When Ctrl+C is pressed, the engine pauses the current action and transitions to confirm_exit.

Running the Demo

go run ./examples/interrupt-demo

Expected Behavior

1. The flow starts and waits for input.
2. Press Ctrl+C.
3. Instead of exiting, the flow jumps to the confirm_exit node:

   “You pressed Ctrl+C. Are you sure you want to exit?”

4. Type y (or yes) to exit gracefully, or n to return to the start.

Windows Note

On Windows, Ctrl+C typically closes the standard input stream (os.Stdin), which can cause race conditions. Trellis automatically detects this and switches to CONIN$ to ensure the signal is caught correctly without killing the input stream.

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