clock_settime(3c)

1clock_settime(3C)        Standard C Library Functions        clock_settime(3C)
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NAME

6       clock_settime,  clock_gettime,  clock_getres  -  high-resolution  clock
7       operations
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SYNOPSIS

10       #include <time.h>
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12       int clock_settime(clockid_t clock_id, const struct timespec *tp);
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15       int clock_gettime(clockid_t clock_id, struct timespec *tp);
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18       int clock_getres(clockid_t clock_id, struct timespec *res);
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DESCRIPTION

22       The clock_settime() function sets the specified clock, clock_id, to the
23       value  specified  by  tp.  Time values that are between two consecutive
24       non-negative integer multiples of the resolution of the specified clock
25       are truncated down to the smaller multiple of the resolution.
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28       The clock_gettime() function returns the current value tp for the spec‐
29       ified clock, clock_id.
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32       The resolution of any clock can be obtained by calling  clock_getres().
33       Clock  resolutions are system-dependent and cannot be set by a process.
34       If the argument res is not NULL, the resolution of the specified  clock
35       is  stored in the location pointed to by res. If res is NULL, the clock
36       resolution is not returned. If the time argument of clock_settime()  is
37       not  a  multiple  of  res, then the value is truncated to a multiple of
38       res.
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41       A clock may be systemwide (that is, visible to all processes)  or  per-
42       process (measuring time that is meaningful only within a process).
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45       A  clock_id of CLOCK_REALTIME is defined in <time.h>. This clock repre‐
46       sents the realtime clock for the system. For  this  clock,  the  values
47       returned  by clock_gettime() and specified by clock_settime() represent
48       the amount of time (in seconds and nanoseconds) since the Epoch.  Addi‐
49       tional  clocks may also be supported. The interpretation of time values
50       for these clocks is unspecified.
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53       A clock_id of CLOCK_HIGHRES represents the non-adjustable, high-resolu‐
54       tion  clock  for  the  system.  For  this  clock, the value returned by
55       clock_gettime(3C)  represents  the  amount  of  time  (in  seconds  and
56       nanoseconds)  since  some  arbitrary time in the past; it is not corre‐
57       lated in any way to the time of day, and thus is not subject to  reset‐
58       ting  or  drifting  by  way  of  adjtime(2), ntp_adjtime(2), settimeof‐
59       day(3C), or clock_settime().  The time source for  this  clock  is  the
60       same as that for gethrtime(3C).
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63       Additional  clocks  may  also  be supported. The interpretation of time
64       values for these clocks is unspecified.
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RETURN VALUES

67       Upon successful completion, 0  is returned. Otherwise, −1  is  returned
68       and errno is set to indicate the error.
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ERRORS

71       The  clock_settime(), clock_gettime() and clock_getres() functions will
72       fail if:
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74       EINVAL    The clock_id argument does not specify a known clock.
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77       ENOSYS    The   functions   clock_settime(),    clock_gettime(),    and
78                 clock_getres() are not supported by this implementation.
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82       The clock_settime() function will fail if:
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84       EINVAL    The  tp  argument to clock_settime() is outside the range for
85                 the given clock ID; or the tp argument specified a nanosecond
86                 value  less  than  zero or greater than or equal to 1000 mil‐
87                 lion.
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91       The clock_settime() function may fail if:
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93       EPERM    The requesting process does not have the appropriate privilege
94                to set the specified clock.
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ATTRIBUTES

98       See attributes(5) for descriptions of the following attributes:
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103       ┌─────────────────────────────┬─────────────────────────────────────┐
104       │ATTRIBUTE TYPE               │ATTRIBUTE VALUE                      │
105       ├─────────────────────────────┼─────────────────────────────────────┤
106       │Interface Stability          │Committed                            │
107       ├─────────────────────────────┼─────────────────────────────────────┤
108       │MT-Level                     │clock_gettime() is Async-Signal-Safe │
109       ├─────────────────────────────┼─────────────────────────────────────┤
110       │Standard                     │See standards(5).                    │
111       └─────────────────────────────┴─────────────────────────────────────┘
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NAME

SYNOPSIS

DESCRIPTION

RETURN VALUES

ERRORS

ATTRIBUTES

SEE ALSO