How to recall select after timeout in C?

Question

I used select for synchronous I/O multiplexing.It will check for any data for 1 second.After 1 second if no data it will display a output (puts("Waited for 1 sec no data");) then it will check again for data.But this is working only at first time then it enters endless loops. Is there any alternative solution for this.

//..............................
//.............................
//Creating listener socket and other sort of things
struct timeval tv;
        tv.tv_sec=1;
        tv.tv_usec=0;

    while(1)
    {
    FD_ZERO(master);


    FD_SET(listener,master);
    fdmax = listener;
    int retval=select(fdmax+1,master, NULL, NULL,&tv);
    printf("retval is %d\n",retval);

            if(retval == -1)
            {
                    perror("Server-select() error");
            }else if(retval)
            {
                    puts("Data available");
                    //If there is no data do some work and checkagain.

            }else
            {
                    puts("Waited for 1 sec no data"); 
                    //If there is no data do some work and checkagain.

            }
      }

Answer 1

From man select:

On Linux, select() modifies timeout to reflect the amount of time not slept; most other implementations do not do this. (POSIX.1-2001 permits either behavior.) This causes problems both when Linux code which reads timeout is ported to other operating systems, and when code is ported to Linux that reuses a struct timeval for multiple select()s in a loop without reinitializing it. Consider timeout to be undefined after select() returns.

So like master, you will have to set tv before each select call.

In my codes, I often have something like:

FD_ZERO(master);
FD_SET(listener,master);
fdmax = listener;

while (1)
{
    struct timeval tv = {1, 0};

    int retval=select(fdmax+1,master, NULL, NULL,&tv);
    printf("retval is %d\n",retval);

    if(retval == -1) {
        perror("Server-select() error");
        break; //  <-- notice the break here
    } else if(retval) {
        puts("Data available");
    } else {
        puts("Waited for 1 sec no data"); 
    }
}