cancel - Cancel a task
cancel stops all processing of a task. If --all is used, all of the current user’s running tasks will be canceled.
If the task has already completed, or no tasks are currently running, a notice will be displayed but the command will succeed.
Cancel all of the current user’s pending tasks
Cancel a transfer task:
$ cancel a04d9872-aec7-11df-9563-1231380722ca
cancel returns 0 unless an internal error occurred or TASKID is not a valid task id. If the task had already completed, a notice will be displayed and cancel will still return 0.