Programming

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


void    on_alarm(int);    /* handler for alarm    */
void    on_input(int);    /* handler for keybd    */
int     set_timer( int which, long initial, long repeat );

volatile sig_atomic_t   finished  = 0;

int main( int argc, char * argv[])
{
    int  fd_flags;
    int k = 0;
    struct sigaction newhandler;    
    sigset_t         blocked;       

    newhandler.sa_handler = on_input;  /* handler function    */
    newhandler.sa_flags   = 0;   

    sigemptyset(&blocked);             
    newhandler.sa_mask = blocked;      
    if ( sigaction(SIGIO, &newhandler, NULL) == -1 )
        perror("sigaction");

    newhandler.sa_handler = on_alarm;  /* handler function    */
    if ( sigaction(SIGALRM, &newhandler, NULL) == -1 )
        perror("sigaction");


    fcntl(0, F_SETOWN, getpid());
    fd_flags = fcntl(0, F_GETFL);
    fcntl(0, F_SETFL, (fd_flags|O_ASYNC));

    set_timer(ITIMER_REAL, 500, 500); 


    while( !finished  )    {         
       pause();
       printf("still in loop and finished = %d\n", finished);
    }
    return 0;
}
void on_input(int signum)
{
    int  c = getchar();          
    if ( c == 'q' )
        finished = 1;
}

void on_alarm(int signum)
{
    static int k = 0;
    printf("call number %d\n", k++);
}


int set_timer( int which, long initial, long repeat )
{
    struct itimerval itimer;
    long secs;

    // initialize initial delay
    secs = initial / 1000 ; 
    itimer.it_value.tv_sec     = secs;    
    itimer.it_value.tv_usec    = (initial - secs*1000 ) * 1000 ;   

    // initialize repeat inveral
    secs = repeat / 1000 ; 
    itimer.it_interval.tv_sec  = secs;     
    itimer.it_interval.tv_usec = (repeat - secs*1000 ) * 1000 ;
    
    return setitimer(which, &itimer, NULL);
}

@skbsd::~/src>./progname
call number 0
still in loop and finished = 0
call number 1
still in loop and finished = 0
call number 2
still in loop and finished = 0
call number 3
still in loop and finished = 0
call number 4
still in loop and finished = 0
call number 5
still in loop and finished = 0
qcall number 6
qcall number 7
qcall number 8
qcall number 9
qcall number 10
<\r here>
still in loop and finished = 1