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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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NANOSLEEP(3P) POSIX Programmer's Manual NANOSLEEP(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.
nanosleep — high resolution sleep
#include <time.h>
int nanosleep(const struct timespec *rqtp, struct timespec *rmtp);
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.
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.
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.
None.
None.
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.
None.
clock_nanosleep(3p), sleep(3p)
The Base Definitions volume of POSIX.1‐2017, time.h(0p)
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)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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