HP-UX Reference (11i v3 07/02) - 2 System Calls (vol 5)

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clocks(2) clocks(2)

NAME

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.If

res 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 can-

not 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.

RETURN VALUE

A return of zero indicates that the call succeeded. A return value of −1 indicates that an error occurred,

and errno is set to indicate the error.

68 Hewlett-Packard Company − 1 − HP-UX 11i Version 3: February 2007