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NANOSLEEP(2)			    Linux Programmer's Manual			     NANOSLEEP(2)

       nanosleep - pause execution for a specified time

       #include <time.h>

       int nanosleep(const struct timespec *req, struct timespec *rem);

       nanosleep  delays  the  execution  of the program for at least the time specified in *req.
       The function can return earlier if a signal has been delivered to  the  process.  In  this
       case, it returns -1, sets errno to EINTR, and writes the remaining time into the structure
       pointed to by rem unless rem is NULL.  The  value  of  *rem  can  then  be  used  to  call
       nanosleep again and complete the specified pause.

       The  structure timespec is used to specify intervals of time with nanosecond precision. It
       is specified in <time.h> and has the form

	      struct timespec
		      time_t  tv_sec;	      /* seconds */
		      long    tv_nsec;	      /* nanoseconds */

       The value of the nanoseconds field must be in the range 0 to 999 999 999.

       Compared to sleep(3) and usleep(3), nanosleep has the advantage of not affecting any  sig-
       nals,  it is standardized by POSIX, it provides higher timing resolution, and it allows to
       continue a sleep that has been interrupted by a signal more easily.

       In case of an error or exception, the nanosleep system call returns -1 instead  of  0  and
       sets errno to one of the following values:

       EINTR  The  pause  has  been interrupted by a non-blocked signal that was delivered to the
	      process. The remaining sleep time has been written into *rem so  that  the  process
	      can easily call nanosleep again and continue with the pause.

       EINVAL The  value in the tv_nsec field was not in the range 0 to 999 999 999 or tv_sec was

       The current implementation of nanosleep is based on the	normal	kernel	timer  mechanism,
       which  has  a  resolution  of  1/HZ s  (i.e, 10 ms on Linux/i386 and 1 ms on Linux/Alpha).
       Therefore, nanosleep pauses always for at least the specified time, however it can take up
       to 10 ms longer than specified until the process becomes runnable again. For the same rea-
       son, the value returned in case of a delivered signal in *rem is usually  rounded  to  the
       next larger multiple of 1/HZ s.

       As  some  applications  require	much  more precise pauses (e.g., in order to control some
       time-critical hardware), nanosleep is also capable of short high-precision pauses. If  the
       process	is scheduled under a real-time policy like SCHED_FIFO or SCHED_RR, then pauses of
       up to 2 ms will be performed as busy waits with microsecond precision.

       POSIX.1b (formerly POSIX.4).

       sleep(3), usleep(3), sched_setscheduler(2), timer_create(2)

Linux 1.3.85				    1996-04-10				     NANOSLEEP(2)
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