Cancellation¶

make-cancellation-token creates a thread-safe token. cancel is idempotent, and cancellation-requested-p observes its state.

(let ((token (process-kit:make-cancellation-token)))
  (process-kit:cancel token)
  (process-kit:run-command
   (process-kit:make-command "/bin/sleep" (list "10"))
   :cancellation-token token
   :on-cancel :return))
;; => a PROCESS-RESULT whose cancelled-p is true

Where a token can be passed¶

Pass the token as cancellation-token to:

run, communicate, run-command, and run-pipeline

Tasks own their cancellation token

communicate-async and run-command-async reject an explicit cancellation-token — the returned process-task owns its own token, and cancel-process (task) is how you cancel it. See Asynchronous Execution.

Escalation and outcome¶

Cancellation sends SIGTERM to the process group, waits the grace period, and sends SIGKILL if needed — the same process-group-wide escalation a timeout uses, so a cancelled shell pipeline's forked descendants are terminated too.

on-cancel :error (the default) signals process-cancelled-error; :return returns a result with process-result-cancelled-p true. See Results and Conditions for the condition's full accessor list.