WNOWAIT

WNOWAIT is a term encountered in discussions of concurrent and asynchronous programming to describe a non-blocking wait or a non-blocking attempt to proceed without blocking the executing thread. It is not a universally standardized API term, but rather a concept that appears in various libraries, samples, and documentation to indicate that a call should return immediately if the requested resource is not yet ready.

In practice, a WNOWAIT-like behavior means that a function or operation will not stall the caller. If the resource or condition is not currently available, the call returns with an indication such as an error code or a special status rather than blocking until the resource becomes ready. This pattern is common in event-driven and poll-based designs, where an application performs work and periodically checks for readiness or handles I/O readiness events.

Because WNOWAIT is not a single standardized option across platforms, its exact meaning and return values vary by API. It is often implemented through non-blocking I/O modes (for example, using non-blocking file descriptors) or through explicit try/attempt patterns that may return immediately with a would-block condition.

Considerations for using a WNOWAIT approach include increased complexity from handling partial results and retry logic, potential busy-wait or polling overhead, and the need for an effective event or notification mechanism to resume work when resources become available. Alternatives include asynchronous callbacks, futures/promises, or proper non-blocking I/O APIs.

In summary, WNOWAIT represents the general idea of non-blocking waiting across various systems, rather than a single standardized feature. When encountered in code, its exact behavior should be verified against the specific platform or library documentation.