Section: POSIX Programmer's Manual (3P)
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.
--- high resolution sleep
int nanosleep(const struct timespec *rqtp, struct timespec *rmtp);
function shall cause the current thread to be suspended from execution
until either the time interval specified by the
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
as measured by the system clock CLOCK_REALTIME.
The use of the
function has no effect on the action or blockage of any signal.
function returns because the requested time has elapsed, its return
value shall be zero.
function returns because it has been interrupted by a signal, it
shall return a value of -1 and set
to indicate the interruption. If the
argument is non-NULL, the
structure referenced by it is updated to contain the amount of time
remaining in the interval (the requested time minus the time actually
arguments may point to the same object. If the
argument is NULL, the remaining time is not returned.
fails, it shall return a value of -1 and set
to indicate the error.
function shall fail if:
function was interrupted by a signal.
argument specified a nanosecond value less than zero or greater than or
equal to 1000 million.
The following sections are informative.
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
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
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
using the remainder of the
functions, such a function requires the use of signals and the
reservation of some signal number. This volume of POSIX.1-2008 requires that
be non-intrusive of the signals function.
function shall return a value of 0 on success and -1 on failure or if
interrupted. This latter case is different from
This was done because the remaining time is returned via an argument
instead of as the return value.
The Base Definitions volume of POSIX.1-2008,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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
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