clock_getres(3) Library Functions Manual clock_getres(3)NAME
clock_getres - Gets the resolution for the specified clock (P1003.1b)
LIBRARY
Realtime Library (librt.so, librt.a)
SYNOPSIS
#include <time.h>
int clock_getres (
clockid_t clock_id,
struct timespec *res);
PARAMETERS
clock_id The clock type used to obtain the resolution. The CLOCK_REALTIME clock is supported and represents the TIME-OF-DAY clock for
the system.
*res A pointer to the timespec data structure that receives the value of the clock's resolution.
DESCRIPTION
The clock_getres function returns the resolution value for the specified clock. If the res argument is NULL, the clock resolution is not
returned.
RETURN VALUES
On a successful call, a value of 0 (zero) is returned.
On an unsuccessful call, a value of -1 is returned and errno is set to indicate that an error occurred.
ERRORS
The clock_getres function fails under the following condition:
[EINVAL] The clock_id argument does not specify a known clock.
RELATED INFORMATION
Functions: time(1), ctime(3), timer_settime(3)
Guide to Realtime Programming delim off
clock_getres(3)
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clock_settime(3RT) Realtime Library Functions clock_settime(3RT)NAME
clock_settime, clock_gettime, clock_getres - high-resolution clock operations
SYNOPSIS
cc [ flag... ] file... -lrt [ library... ]
#include <time.h>
int clock_settime(clockid_t clock_id, const struct timespec *tp);
int clock_gettime(clockid_t clock_id, struct timespec *tp);
int clock_getres(clockid_t clock_id, struct timespec *res);
DESCRIPTION
The clock_settime() function sets the specified clock, clock_id, to the value specified by tp. Time values that are between two consecutive
non-negative integer multiples of the resolution of the specified clock are truncated down to the smaller multiple of the resolution.
The clock_gettime() function returns the current value tp for the specified clock, clock_id.
The resolution of any clock can be obtained by calling clock_getres(). Clock resolutions are system-dependent and cannot be set by a
process. If the argument res is not NULL, the resolution of the specified clock is stored in the location pointed to by res. If res is
NULL, the clock resolution is not returned. If the time argument of clock_settime() is not a multiple of res, then the value is truncated
to a multiple of res.
A clock may be systemwide (that is, visible to all processes) or per-process (measuring time that is meaningful only within a process).
A clock_id of CLOCK_REALTIME is defined in <time.h>. This clock represents the realtime clock for the system. For this clock, the values
returned by clock_gettime() and specified by clock_settime() represent the amount of time (in seconds and nanoseconds) since the Epoch.
Additional clocks may also be supported. The interpretation of time values for these clocks is unspecified.
A clock_id of CLOCK_HIGHRES represents the non-adjustable, high-resolution clock for the system. For this clock, the value returned by
clock_gettime(3RT) represents the amount of time (in seconds and nanoseconds) since some arbitrary time in the past; it is not correlated
in any way to the time of day, and thus is not subject to resetting or drifting by way of adjtime(2), ntp_adjtime(2), settimeofday(3C), or
clock_settime(). The time source for this clock is the same as that for gethrtime(3C).
Additional clocks may also be supported. The interpretation of time values for these clocks is unspecified.
RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
The clock_settime(), clock_gettime() and clock_getres() functions will fail if:
EINVAL The clock_id argument does not specify a known clock.
ENOSYS The functions clock_settime(), clock_gettime(), and clock_getres() are not supported by this implementation.
The clock_settime() function will fail if:
EINVAL The tp argument to clock_settime() is outside the range for the given clock ID; or the tp argument specified a nanosecond
value less than zero or greater than or equal to 1000 million.
The clock_settime() function may fail if:
EPERM The requesting process does not have the appropriate privilege to set the specified clock.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-------------------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-------------------------------------+
|Interface Stability |Standard |
+-----------------------------+-------------------------------------+
|MT-Level |clock_gettime() is Async-Signal-Safe |
+-----------------------------+-------------------------------------+
SEE ALSO time(2), ctime(3C), gethrtime(3C), time.h(3HEAD), timer_gettime(3RT), attributes(5), standards(5)SunOS 5.10 28 Jun 2002 clock_settime(3RT)