timergettime

timer_gettime is a POSIX function that retrieves the current settings of a per-process timer. It is part of the real-time timers interface and is commonly described as timer_gettime; some libraries or documentation may refer to it as timergettime.

Signature and parameters: int timer_gettime(timer_t timerid, struct itimerspec *tp); timerid is a timer identifier obtained from timer_create, and tp is a pointer to an itimerspec structure that will be filled with the timer’s current values.

Itimerspec fields: The itimerspec structure contains two timespec values: IT_INTERVAL and IT_VALUE. It_value represents the time remaining until the next expiration, while it_interval specifies the timer’s rearm interval for periodic timers.

Behavior: timer_gettime writes into tp the current expiration settings. If it_value is zero, the timer has no scheduled expiration at the moment. If it_interval is non-zero, the timer will reload with that interval after each expiration, enabling periodic behavior.

Return value and errors: On success, timer_gettime returns 0. On error, it returns -1 and sets errno. Common errors include EFAULT if tp points outside the process’s accessible address space, and EINVAL if timerid is invalid or not a real-time timer created with timer_create.

Typical usage: After creating a timer with timer_create, you can call timer_gettime to inspect how much time remains before the next expiration and what the current reload interval is, without modifying the timer’s configuration. This is useful for monitoring timer state in event-driven programs.

See also: timer_create, timer_settime, timer_delete, clock_gettime, and related timing facilities such as nanosleep and timerfd in Linux implementations. Note that some documentation may refer to this function as timergettime.