Represents an optional interrupt request.

A constant for a no request. clr nothing does nothing.

req ~seconds requests an interrupt in the form of a signal delivered to the thread that made the request within the specified number of seconds. Blocking Unix IO calls typically raise an error with the Unix.EINTR error code when they are interrupted by a signal.

Regardless of whether the signal gets triggered or a system call gets interrupted, the request must be cleared.

⚠️ Due to limitations of the OCaml system modules and unlike with typical timeout mechanisms, the interrupt may also be triggered sooner.

clr req either cancels or acknowledges the interrupt request. Every req must be cleared!