nanosleep(3p) — Linux manual page

NANOSLEEP(3P)           POSIX Programmer's Manual          NANOSLEEP(3P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       nanosleep — high resolution sleep

SYNOPSIS

       #include <time.h>

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

DESCRIPTION

       The nanosleep() function shall cause 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 shall
       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 VALUE

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

       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 can 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.

ERRORS

       The nanosleep() function shall 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.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       It is common to suspend execution of a thread for an interval in
       order to poll the status of a non-interrupting function. A large
       number of actual needs can be met with a simple extension to
       sleep() that provides finer resolution.

       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.1‐2017 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.

FUTURE DIRECTIONS

       None.

SEE ALSO

       clock_nanosleep(3p), sleep(3p)

       The Base Definitions volume of POSIX.1‐2017, time.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                     NANOSLEEP(3P)

Pages that refer to this page: time.h(0p), clock_getres(3p), clock_nanosleep(3p), sleep(3p)

---