# Class Shell_uq.system_handler_engine

    class system_handler_engine : Unixqueue.event_system -> [unit] system_handler_engine_type

This engine implements a `Shell_sys.system_handler`, and can be used to watch an already started `job_instance` as created by `Shell_sys.run_job` until the job is done. It is necessary to `Shell_sys.register_job` at the system handler.

When the job terminates the status of the engine changes to ``Done ()`. The status of the engine does not reflect whether the job was successful `Job_ok` or has failed `Job_error`.

The engine status ``Error` indicates an internal error. It is also used when callback functions raise exceptions.

When the engine goes to ``Error` or ``Aborted`, the job is terminated ( `Shell_sys.abandon_job` ).