huschi.net

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  sys-
       tem.  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 may point to the same object. If the rmtp argu-
       ment 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 pro-
       vides 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 facili-
       ties. Although it is possible to write a function  with  similar  func-
       tionality  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.1-2008 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(), sleep()
       The Base Definitions volume of POSIX.1-2008, <time.h>
COPYRIGHT
       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 Electri-
       cal  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 http://www.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                        NANOSLEEP(3P)