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System Calls getitimer(2)
NAME
getitimer, setitimer - get or set value of interval timer
SYNOPSIS
#include <sys/time.h>
int getitimer(int which, struct itimerval *value);
int setitimer(int which, const struct itimerval *value,
struct itimerval *ovalue);
DESCRIPTION
The system provides each process with four interval timers,
defined in <sys/time.h>. The getitimer() function stores the
current value of the timer specified by which into the
structure pointed to by value. The setitimer() function call
sets the value of the timer specified by which to the value
specified in the structure pointed to by value, and if
ovalue is not NULL, stores the previous value of the timer
in the structure pointed to by ovalue.
A timer value is defined by the itimerval structure (see
gettimeofday(3C)) for the definition of timeval), which
includes the following members:
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
The it_value member indicates the time to the next timer
expiration. The it_interval member specifies a value to be
used in reloading it_value when the timer expires. Setting
it_value to 0 disables a timer, regardless of the value of
it_interval. Setting it_interval to 0 disables a timer after
its next expiration (assuming it_value is non-zero).
Time values smaller than the resolution of the system clock
are rounded up to the resolution of the system clock, except
for ITIMER_REALPROF, whose values are rounded up to the
resolution of the profiling clock. The four timers are as
follows:
ITIMER_REAL
Decrements in real time. A SIGALRM signal is delivered
when this timer expires.
SunOS 5.10 Last change: 6 Jun 2001 1
System Calls getitimer(2)
ITIMER_VIRTUAL
Decrements in process virtual time. It runs only when
the process is executing. A SIGVTALRM signal is
delivered when it expires.
ITIMER_PROF
Decrements both in process virtual time and when the
system is running on behalf of the process. It is
designed to be used by interpreters in statistically
profiling the execution of interpreted programs. Each
time the ITIMER_PROF timer expires, the SIGPROF signal
is delivered. Because this signal may interrupt in-
progress functions, programs using this timer must be
prepared to restart interrupted functions.
ITIMER_REALPROF
Decrements in real time. It is designed to be used for
real-time profiling of multithreaded programs. Each time
the ITIMER_REALPROF timer expires, one counter in a set
of counters maintained by the system for each light-
weight process (lwp) is incremented. The counter
corresponds to the state of the lwp at the time of the
timer tick. All lwps executing in user mode when the
timer expires are interrupted into system mode. When
each lwp resumes execution in user mode, if any of the
elements in its set of counters are non-zero, the SIG-
PROF signal is delivered to the lwp. The SIGPROF signal
is delivered before any other signal except SIGKILL.
This signal does not interrupt any in-progress function.
A siginfo structure, defined in <sys/siginfo.h>, is
associated with the delivery of the SIGPROF signal, and
includes the following members:
si_tstamp; /* high resolution timestamp */
si_syscall; /* current syscall */
si_nsysarg; /* number of syscall arguments */
si_sysarg[]; /* actual syscall arguments */
si_fault; /* last fault type */
si_faddr; /* last fault address */
si_mstate[]; /* ticks in each microstate */
The enumeration of microstates (indices into si_mstate)
SunOS 5.10 Last change: 6 Jun 2001 2
System Calls getitimer(2)
is defined in <sys/msacct.h>.
RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, -1 is
returned and errno is set to indicate the error.
ERRORS
The getitimer() and setitimer() functions will fail if:
EINVAL The specified number of seconds is greater
than 100,000,000, the number of microseconds
is greater than or equal to 1,000,000, or
the which argument is unrecognized.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
alarm(2), gettimeofday(3C), sleep(3C), sysconf(3C), attri-
butes(5), standards(5)
NOTES
The microseconds field should not be equal to or greater
than one second.
The setitimer() function is independent of the alarm() func-
tion.
Do not use setitimer(ITIMER_REAL) with the sleep() routine.
A sleep(3C) call wipes out knowledge of the user signal
handler for SIGALRM.
The ITIMER_PROF and ITIMER_REALPROF timers deliver the same
signal and have different semantics. They cannot be used
together.
The granularity of the resolution of alarm time is
platform-dependent.
SunOS 5.10 Last change: 6 Jun 2001 3
Man(1) output converted with
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This page was generated on Wed Sep 12 11:26:59 GMT 2007
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