POSIXtimerit

POSIX timers are a feature of the POSIX standard, which defines a set of APIs for operating systems to ensure compatibility and portability of applications. POSIX timers provide a mechanism for applications to create, manage, and handle time-based events. They are particularly useful for tasks that require precise timing, such as real-time applications, scheduling, and periodic tasks.

POSIX timers can be categorized into two types: interval timers and per-process timers. Interval timers are used to generate periodic signals at specified intervals, while per-process timers are used to generate a single signal after a specified time interval. Both types of timers can be set to be either relative or absolute, depending on whether the specified time is relative to the current time or an absolute point in time.

The POSIX timer API includes functions for creating, deleting, and manipulating timers. The timer_create function is used to create a new timer, while timer_delete is used to delete an existing timer. The timer_settime function is used to set the time for a timer, and timer_gettime is used to retrieve the current time for a timer. The timer_getoverrun function is used to determine the number of timer expirations that have occurred but have not yet been delivered.

POSIX timers are implemented using the SIGEV_SIGNAL or SIGEV_THREAD notification mechanism. When a timer expires, it can generate a signal or invoke a thread function, allowing the application to handle the timer expiration event. This makes POSIX timers a powerful tool for implementing time-based functionality in applications.