setitimer(2)
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setitimer System Call
Set one of the interval timers.
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SYNTAX
#include <sys/time.h>
int setitimer (which_timer, new_state_ptr, old_state_ptr)
int which_timer;
struct itimerval *new_state_ptr;
struct itimerval *old_state_ptr;
PARAMETERS
which_timer Specifies which of the three available timers to
set. Can be ITIMER_REAL, ITIMER_VIRTUAL, or
ITIMER_PROF.
new_state_ptr The value to set in the specified timer.
old_state_ptr The previous value of the specified timer is
returned in <old_state_ptr> if non-zero.
DESCRIPTION
Setitimer() can set one of three timers: ITIMER_REAL,
ITIMER_VIRTUAL, or ITIMER_PROF.
The ITIMER_REAL timer decrements in real-time. A SIGALRM signal
is delivered to the calling process when the timer expires.
The ITIMER_VIRTUAL timer decrements when the process is running
in user code. A SIGVTALRM signal is delivered to the calling
process when the timer expires.
The ITIMER_PROF timer decrements both when the process is running
in user code and when the system is running in behalf of the
process. It is designed to be used by interpreters in
statistically profiling the execution of interpreted programs. A
SIGPROF signal is delivered to the calling process when the timer
expires.
The timeval structure defined in <sys/time.h> is of the form:
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setitimer(2)
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.
RETURN VALUE
0 Call was successful
-1 An error occurred. Errno is set to indicate
error.
EXCEPTIONS
Errno may be set to one of the following error codes:
EFAULT the <new_state_ptr> specified a bad address
EINVAL invalid argument
SEE ALSO
The related system calls: alarm, getitimer, sigvec
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