Other clock sources
We've seen the clock source CLOCK_REALTIME, and mentioned that a POSIX conforming implementation may supply as many different clock sources as it feels like, provided that it at least provides CLOCK_REALTIME.
Kernel timeouts QNX Neutrino lets you have a timeout associated with all kernel blocking states. We talked about the blocking states in the Processes and Threads chapter, in the section “Kernel states.” Most often, you'll want to use this with message passing; a client will send a message to a server, but the client won't want to wait “forever” for the server to respond. In that case, a kernel timeout is suitable. Kernel timeouts are also useful with the pthread_join() function. You might want to wait for a thread to finish, but you might not want to wait too long.
Summary
We've looked at QNX Neutrino's time-based functions, including timers and how they can be used, as well as kernel timeouts. Relative timers provide some form of event “in a certain number of seconds,” while absolute timers provide this event “at a certain time.” Timers (and, generally speaking, the struct sigevent) can cause the delivery of a pulse, a signal, or a thread to start.