1NANOSLEEP(3P) POSIX Programmer's Manual NANOSLEEP(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 nanosleep - high resolution sleep (REALTIME)
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15 #include <time.h>
16 int nanosleep(const struct timespec *rqtp, struct timespec *rmtp);
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21 The nanosleep() function shall cause the current thread to be suspended
22 from execution until either the time interval specified by the rqtp
23 argument has elapsed or a signal is delivered to the calling thread,
24 and its action is to invoke a signal-catching function or to terminate
25 the process. The suspension time may be longer than requested because
26 the argument value is rounded up to an integer multiple of the sleep
27 resolution or because of the scheduling of other activity by the sys‐
28 tem. But, except for the case of being interrupted by a signal, the
29 suspension time shall not be less than the time specified by rqtp, as
30 measured by the system clock CLOCK_REALTIME.
31 The use of the nanosleep() function has no effect on the action or
33 blockage of any signal.
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36 If the nanosleep() function returns because the requested time has
37 elapsed, its return value shall be zero.
38 If the nanosleep() function returns because it has been interrupted by
40 a signal, it shall return a value of -1 and set errno to indicate the
41 interruption. If the rmtp argument is non-NULL, the timespec structure
42 referenced by it is updated to contain the amount of time remaining in
43 the interval (the requested time minus the time actually slept). If the
44 rmtp argument is NULL, the remaining time is not returned.
45 If nanosleep() fails, it shall return a value of -1 and set errno to
47 indicate the error.
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50 The nanosleep() function shall fail if:
51 EINTR The nanosleep() function was interrupted by a signal.
53 EINVAL The rqtp argument specified a nanosecond value less than zero or
55 greater than or equal to 1000 million.
56 The following sections are informative.
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61 None.
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64 None.
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67 It is common to suspend execution of a process for an interval in order
68 to poll the status of a non-interrupting function. A large number of
69 actual needs can be met with a simple extension to sleep() that pro‐
70 vides finer resolution.
71 In the POSIX.1-1990 standard and SVR4, it is possible to implement such
73 a routine, but the frequency of wakeup is limited by the resolution of
74 the alarm() and sleep() functions. In 4.3 BSD, it is possible to write
75 such a routine using no static storage and reserving no system facili‐
76 ties. Although it is possible to write a function with similar func‐
77 tionality to sleep() using the remainder of the timer_*() functions,
78 such a function requires the use of signals and the reservation of some
79 signal number. This volume of IEEE Std 1003.1-2001 requires that
80 nanosleep() be non-intrusive of the signals function.
81 The nanosleep() function shall return a value of 0 on success and -1 on
83 failure or if interrupted. This latter case is different from sleep().
84 This was done because the remaining time is returned via an argument
85 structure pointer, rmtp, instead of as the return value.
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88 None.
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91 sleep(), the Base Definitions volume of IEEE Std 1003.1-2001, <time.h>
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94 Portions of this text are reprinted and reproduced in electronic form
95 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
96 -- Portable Operating System Interface (POSIX), The Open Group Base
97 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
98 Electrical and Electronics Engineers, Inc and The Open Group. In the
99 event of any discrepancy between this version and the original IEEE and
100 The Open Group Standard, the original IEEE and The Open Group Standard
101 is the referee document. The original Standard can be obtained online
102 at http://www.opengroup.org/unix/online.html .
103IEEE/The Open Group 2003 NANOSLEEP(3P)