int
getitimer(
int which
, struct itimerval *value
)
int
setitimer(
int which
, const struct itimerval * restrict value
, struct itimerval * restrict ovalue
)
sys/time.h<.blm Pp
. >
The
getitimer(
)
call returns the current value for the timer specified in
which
in the structure at
value
.
The
setitimer(
)
call sets a timer to the specified
value
(returning the previous value of the timer if
ovalue
is non-nil).
A timer value is defined by the
itimerval
structure:
struct itimerval {
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
};
If
it_value
is non-zero, it indicates the time to the next timer expiration.
If
it_interval
is non-zero, it specifies a value to be used in reloading
it_value
when the timer expires.
Setting
it_value
to 0 disables a timer.
Setting
it_interval
to 0 causes a timer to be disabled after its next expiration (assuming
it_value
is non-zero).
Time values smaller than the resolution of the system clock are rounded up to this resolution (typically 10 milliseconds).
The
ITIMER_REAL
timer decrements in real time.
A
SIGALRM
signal is
delivered when this timer expires.
The
ITIMER_VIRTUAL
timer decrements in process virtual time.
It runs only when the process is executing.
A
SIGVTALRM
signal
is delivered when it expires.
The
ITIMER_PROF
timer 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
system calls, programs using this timer must be prepared to
restart interrupted system calls.
sys/time.h<.blm Pp
. >
timerclear(
)
sets a time value to zero,
timerisset(
)
tests if a time value is non-zero,
timercmp(
)
compares two time values,
timeradd(
)
adds a time value to another time value,
timersub(
)
computes the time difference between two time values.
)
and
setitimer(
)
will fail if:
EFAULT
]
value
parameter specified a bad address.
EINVAL
]
value
parameter specified a time that was too large
to be handled.
)
function call appeared in
4.2BSD.