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demo_itimer.c
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demo_itimer.c
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/*
* Interval-timer demo program.
* Hebrew University OS course.
* Questions: os@cs.huji.ac.il
*/
#include <stdio.h>
#include <signal.h>
#include <sys/time.h>
int gotit = 0;
void timer_handler(int sig)
{
gotit = 1;
printf("Timer expired\n");
}
int main(void) {
struct sigaction sa;
struct itimerval timer;
// Install timer_handler as the signal handler for SIGVTALRM.
sa.sa_handler = &timer_handler;
if (sigaction(SIGVTALRM, &sa,NULL) < 0) {
printf("sigaction error.");
}
// Configure the timer to expire after 1 sec... */
timer.it_value.tv_sec = 1; // first time interval, seconds part
timer.it_value.tv_usec = 0; // first time interval, microseconds part
// configure the timer to expire every 3 sec after that.
timer.it_interval.tv_sec = 3; // following time intervals, seconds part
timer.it_interval.tv_usec = 0; // following time intervals, microseconds part
// Start a virtual timer. It counts down whenever this process is executing.
if (setitimer (ITIMER_VIRTUAL, &timer, NULL)) {
printf("setitimer error.");
}
for(;;) {
if (gotit) {
printf("Got it!\n");
gotit = 0;
}
}
}