set_ticker.c

understanding unix/linux programming source code(bruce molay)

#include	<stdio.h>
#include        <sys/time.h>
#include        <signal.h>

/*
 *      set_ticker.c
 *          set_ticker( number_of_milliseconds )
 *                   arranges for the interval timer to issue
 *                   SIGALRM's at regular intervals
 *          returns -1 on error, 0 for ok
 *
 *      arg in milliseconds, converted into micro seoncds
 */


set_ticker( n_msecs )
{
        struct itimerval new_timeset;
        long    n_sec, n_usecs;

        n_sec = n_msecs / 1000 ;
        n_usecs = ( n_msecs % 1000 ) * 1000L ;

        new_timeset.it_interval.tv_sec  = n_sec;        /* set reload  */
        new_timeset.it_interval.tv_usec = n_usecs;      /* new ticker value */
        new_timeset.it_value.tv_sec     = n_sec  ;      /* store this   */
        new_timeset.it_value.tv_usec    = n_usecs ;     /* and this     */

	return setitimer(ITIMER_REAL, &new_timeset, NULL);
}