|NANOSLEEP(3P)||POSIX Programmer's Manual||NANOSLEEP(3P)|
int nanosleep(const struct timespec *rqtp, struct timespec *rmtp);
The use of the nanosleep() function has no effect on the action or blockage of any signal.
If the nanosleep() function returns because it has been interrupted by a signal, it shall return a value of −1 and set errno to indicate the interruption. If the rmtp argument is non-NULL, the timespec structure referenced by it is updated to contain the amount of time remaining in the interval (the requested time minus the time actually slept). The rqtp and rmtp arguments may point to the same object. If the rmtp argument is NULL, the remaining time is not returned.
If nanosleep() fails, it shall return a value of −1 and set errno to indicate the error.
- The nanosleep() function was interrupted by a signal.
- The rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million.
The following sections are informative.
In the POSIX.1‐1990 standard and SVR4, it is possible to implement such a routine, but the frequency of wakeup is limited by the resolution of the alarm() and sleep() functions. In 4.3 BSD, it is possible to write such a routine using no static storage and reserving no system facilities. Although it is possible to write a function with similar functionality to sleep() using the remainder of the timer_*() functions, such a function requires the use of signals and the reservation of some signal number. This volume of POSIX.1‐2008 requires that nanosleep() be non-intrusive of the signals function.
The nanosleep() function shall return a value of 0 on success and −1 on failure or if interrupted. This latter case is different from sleep(). This was done because the remaining time is returned via an argument structure pointer, rmtp, instead of as the return value.
The Base Definitions volume of POSIX.1‐2008, <time.h>
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