Creates a new dispatch source to monitor low-level system events.
- iOS 4.0+
- macOS 10.6+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
The underlying system handle to monitor. The interpretation of this argument is determined by the constant provided in the type parameter.
A mask of flags specifying which events are desired. The interpretation of this argument is determined by the constant provided in the type parameter.
The dispatch queue to which the event handler block is submitted.
A new dispatch source object or
NULL if the dispatch source could not be created.
Dispatch sources are not reentrant. Any events received while the dispatch source is suspended or while the event handler block is currently executing are coalesced and delivered after the dispatch source is resumed or the event handler block has returned.
Dispatch sources are created in a suspended state. After creating the source and setting any desired attributes (for example, the handler or the context), your application must call
dispatch to begin event delivery.