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HP-UX 11i Version 3: February 2007

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nanosleep() — high resolution sleep


#include <time.h> int nanosleep( const struct timespec *rqtp, struct timespec *rmtp );


The nanosleep() function causes the current thread to be suspended from execution until either the time interval specified by the rqtp argument has elapsed, or a signal is delivered to the calling thread and its action is to invoke a signal-catching function or to terminate the process. The suspension time may be longer than that requested because the argument value is rounded up to an integer multiple of the sleep resolution or because of the scheduling of other activity by the system. However, with the exception of the case of being interrupted by a signal, the suspension time will not be less than the time specified by rqtp, as measured by the system clock, CLOCK_REALTIME.

The use of the nanosleep() function has no effect on the action or blockage of any signal.


If the nanosleep() function returns because the requested time has elapsed, its return value is zero.

If the nanosleep() function returns because it has been interrupted by a signal, the function returns a value of -1 and sets 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). If the rmtp argument is NULL, the remaining time is not returned.

If nanosleep() fails, it returns a value of -1 and sets errno to indicate the error.


If any of the following conditions occur, the nanosleep() function returns -1 and sets errno (see errno(2)) to the corresponding value:


The rqtp or rmtp arguments specify an invalid address.


nanosleep() was interrupted by a signal.


The rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million.


The function nanosleep() is not supported by this implementation.


Suspend execution of the current thread for half a second:

#include <time.h> #include <errno.h> struct timespec interval, remainder; interval.tv_sec = 0; interval.tv_nsec = 500000000; if (nanosleep(&interval, &remainder) == -1) { if (errno == EINTR) { (void)printf("nanosleep interrupted\n"); (void)printf("Remaining secs: %d\n", remainder.tv_sec); (void)printf("Remaining nsecs: %d\n", remainder.tv_nsec); } else perror("nanosleep"); }


nanosleep was derived from the proposed IEEE POSIX P1003.4 Standard, Draft 14.


nanosleep(): POSIX.4

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