mwait.c

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

void on_sigalrm(int sig) {
    return;
}

int main(int argc, char *argv[]) {
    float wait;
    int sig;
    sigset_t sigset;
    struct itimerval new_value = {
       (struct timeval){ (time_t)0, (suseconds_t)0 },
       (struct timeval){ (time_t)0, (suseconds_t)0 },
    };

    if(argc < 2)
        return 1;

    wait = strtof(argv[1], (void *)0);
    if(wait <= 0)
        return 1;
    
    new_value.it_value.tv_sec = (time_t)wait;
    new_value.it_value.tv_usec = (suseconds_t)((wait - (int)wait) * 1000000);

    sigemptyset(&sigset);
    sigaddset(&sigset, SIGALRM);
    signal(SIGALRM, &on_sigalrm);

    setitimer(ITIMER_REAL, &new_value, (void *)0);
    sigwait(&sigset, &sig);

    return 0;
}