Одновременное выполнение действий без использования потоков/процессов

// взято здесь [url]http://www.cplusplus.com/forum/unices/25213/[/url]
#include <time.h>
#include <sys/time.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
/*
**   NOTE NOTE NOTE NOTE
**
**  you will need to link: (use LDFLAGS)
**
**  -lrt -lpthread
*/
 
#define SZ 46
long int overruns[SZ];
 
void callback(union sigval  arg) {
 
    timer_t * p =  (timer_t *) arg.sival_ptr;;
    int delay = timer_getoverrun(*p);
    printf("delay = %d\n", delay);
 
    // count overruns, which are timer intervals skipped
    if (delay<SZ) {
    overruns[delay]++;
    } else {
    timer_delete(*p);
    return ;
    }
 
    return;
}
 
timer_t timerid;
int main (int argc, char ** argv) {
 
    struct sigevent se;
    struct itimerspec ts;
    long int nsec;
    long int msec;
    long int sec;
 
    if(argc<2) {
    fputs("time milliseconds?\n",stderr);
    exit(1);
    }
    msec = atoi(argv[1]);
    fprintf(stderr, "got  %ld\n", msec);
    sec = (msec / 1000); 
    msec %= 1000;
    nsec = msec * 1e06;;
 
    se.sigev_notify = SIGEV_THREAD;
    se.sigev_value.sival_ptr = &timerid;
    se.sigev_notify_function = callback;
    se.sigev_notify_attributes = NULL;
 
    if ( -1 == timer_create(CLOCK_REALTIME, &se, &timerid)) {
    perror("timer_create:");
    return(1);
    }
 
    ts.it_value.tv_sec = sec;
    ts.it_value.tv_nsec = nsec;
    ts.it_interval.tv_sec = sec;
    ts.it_interval.tv_nsec = nsec ;
    printf("nanosex = %ld\n", ts.it_interval.tv_nsec);
    printf("seconds = %ld\n", ts.it_interval.tv_sec);
 
    if (-1 == timer_settime(timerid, 0, &ts, NULL)) {
    perror("timer_settime:");
    }
    getchar();   // press a key to stop
 
    int t;
    for(t=0; t<SZ; t++) {
 
    printf("overruns[%02d] = %ld\n", t, overruns[t]);
    }
 
 
    return 0;
}