nanosleep(2) [redhat man page]

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

NAME

       nanosleep - pause execution for a specified time

SYNOPSIS

       #include <time.h>

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

DESCRIPTION

       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 signals, 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.

ERRORS

       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 negative.

BUGS

       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 reason, 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.

CONFORMING TO

       POSIX.1b (formerly POSIX.4).

SEE ALSO

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

Linux 1.3.85							    1996-04-10							      NANOSLEEP(2)

Check Out this Related Man Page

nanosleep(3C)						   Standard C Library Functions 					     nanosleep(3C)

NAME

       nanosleep - high resolution sleep

SYNOPSIS

       #include <time.h>

       int nanosleep(const struct timespec *rqtp,
	    struct timespec *rmtp);

DESCRIPTION

       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 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. But, except for 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.

RETURN VALUES

       If the nanosleep() function returns because the requested time has elapsed, its return value is 0.

       If the nanosleep() function returns because it has been interrupted by a signal, the function returns a value of -1 and sets errno to indi-
       cate 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 -1 and sets errno to indicate the error.

ERRORS

       The nanosleep() function will fail if:

       EINTR	 The nanosleep() function was interrupted by a signal.

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

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

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |ATTRIBUTE TYPE		     |ATTRIBUTE VALUE		   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sleep(3C), time.h(3HEAD), attributes(5), standards(5)

SunOS 5.11							    5 Feb 2008							     nanosleep(3C)

Linux and UNIX Man Pages

nanosleep(2) [redhat man page]

Check Out this Related Man Page