получить и установить значение интервального таймера (get and set value of interval timer)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
getitimer, setitimer — get and set value of interval timer
Синопсис (Synopsis)
#include <sys/time.h>
int getitimer(int which, struct itimerval *value);
int setitimer(int which, const struct itimerval *restrict value,
struct itimerval *restrict ovalue);
Описание (Description)
The getitimer() function shall store the current value of the
timer specified by which into the structure pointed to by value.
The setitimer() function shall set the timer specified by which
to the value specified in the structure pointed to by value, and
if ovalue is not a null pointer, store the previous value of the
timer in the structure pointed to by ovalue.
A timer value is defined by the itimerval structure, specified in
<sys/time.h>. If it_value is non-zero, it shall indicate the
time to the next timer expiration. If it_interval is non-zero,
it shall specify a value to be used in reloading it_value when
the timer expires. Setting it_value to 0 shall disable a timer,
regardless of the value of it_interval. Setting it_interval to 0
shall disable a timer after its next expiration (assuming
it_value is non-zero).
Implementations may place limitations on the granularity of timer
values. For each interval timer, if the requested timer value
requires a finer granularity than the implementation supports,
the actual timer value shall be rounded up to the next supported
value.
An XSI-conforming implementation provides each process with at
least three interval timers, which are indicated by the which
argument:
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.
ITIMER_REAL Decrements in real time. A SIGALRM signal is
delivered when this timer expires.
ITIMER_VIRTUAL
Decrements in process virtual time. It runs only
when the process is executing. A SIGVTALRM signal
is delivered when it expires.
The interaction between setitimer() and alarm() or sleep() is
unspecified.
Возвращаемое значение (Return value)
Upon successful completion, getitimer() or setitimer() shall
return 0; otherwise, -1 shall be returned and errno set to
indicate the error.
Ошибки (Error)
The setitimer() function shall fail if:
EINVAL The value argument is not in canonical form. (In canonical
form, the number of microseconds is a non-negative integer
less than 1000000 and the number of seconds is a non-
negative integer.)
The getitimer() and setitimer() functions may fail if:
EINVAL The which argument is not recognized.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Applications should use the timer_gettime() and timer_settime()
functions instead of the obsolescent getitimer() and setitimer()
functions, respectively.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
The getitimer() and setitimer() functions may be removed in a
future version.
Смотри также (See also)
alarm(3p), exec(1p), sleep(3p), timer_getoverrun(3p)
The Base Definitions volume of POSIX.1‐2017, signal.h(0p),
sys_time.h(0p)
