clocks(2)clocks(2)NAMEclock_settime(), clock_gettime(), clock_getres() - clock operations
SYNOPSISDESCRIPTIONclock_settime()
The function sets the specified clock, to the value specified by 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.
clock_gettime()
The function returns the current value for the specified clock,
clock_getres()
The resolution of any clock can be obtained by calling Clock resolu‐
tions are implementation defined and are not settable by a process. If
the argument is not NULL, the resolution of the specified clock is
stored into the location pointed to by If is NULL, the clock resolution
is not returned.
A clock may be system wide, that is, visible to all processes; or per-
process, measuring time that is meaningful only within a process.
The following clocks are supported:
This clock represents the realtime clock for the system.
For this clock, the values returned by and specified
by represent the amount of time (in seconds and
nanoseconds) since the Epoch. It is a system wide
clock. The privilege is required to set this clock.
Processes owned by the superuser have this privi‐
lege. Processes owned by other users may have this
privilege, depending on system configuration. See
privileges(5) for more information about privileged
access on systems that support fine-grained privi‐
leges.
This clock represents the amount of time (in seconds and
nanoseconds)
that the calling process has spent executing code in
the user's context. It is a per-process clock. It
cannot be set by the user.
This clock represents the amount of time (in seconds and
nanoseconds)
that the calling process has spent executing code in
both the user's context and in the operating system
on behalf of the calling process. It is a per-
process clock. It cannot be set by the user.
These clocks are high resolution hardware clocks
present on HP-RT realtime systems. It is included
here so that applications accessing this hardware
can be compiled on HP-UX systems and then ported to
an HP-RT target. HP-UX does not support or
RETURN VALUE
A return of zero indicates that the call succeeded. A return value of
−1 indicates that an error occurred, and is set to indicate the error.
ERRORS
If any of the following conditions occur, the and functions return −1
and set (see errno(2)) to the corresponding value:
The functions
and are not supported by this implementation.
The argument does not specify a known clock.
The argument to is outside the range for the given
The argument specified a nanosecond value less than zero
or greater than or equal to 1000 million.
The requesting process does not have the necessary privileges to
set the
specified clock.
The or argument points to an invalid address.
EXAMPLES
Advance the system wide realtime clock approximately one hour:
Get the resolution of the user profiling clock:
AUTHOR
and were derived from the proposed IEEE POSIX P1003.4 Standard, Draft
14.
SEE ALSOtimers(2), privileges(5).
STANDARDS CONFORMANCEclocks(2)