HP-UX Reference (11i v2 07/12) - 2 System Calls (vol 5)

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clocks(2) clocks(2)

NAME

clocks: clock_settime(), clock_gettime(), clock_getres() - clock operations

SYNOPSIS

#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

clock_settime()

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.

clock_gettime()

The

clock_gettime() function returns the current value

tp for the speciﬁed clock, clock_id.

clock_getres()

The resolution of any clock can be obtained by calling

clock_getres()

. Clock resolutions are imple-

mentation deﬁned and are not settable by a process. If the argument

res is not NULL, the resolution of

the speciﬁed clock is stored into the location pointed to by

res.Ifres

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 mean-

ingful only within a process.

The following clocks are supported:

CLOCK_REALTIME

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. It is a system wide clock. The

SYSATTR privilege is

required to set this clock. Processes owned by the superuser have this privilege. 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

privileges.

CLOCK_VIRTUAL

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.

CLOCK_PROFILE

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.

RTTIMER0 RTTIMER1

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 RTTIMER0 or RTTIMER1.

HP-UX 11i Version 2: December 2007 Update − 1 − Hewlett-Packard Company 65