codice:
#include <stdio.h>
#include <stdlib.h>

#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int main(void) {

    fd_set rfds;
    struct timeval tv;
    int retval;
    char  ch;

   /* Watch stdin (fd 0) to see when it has input. */
    FD_ZERO(&rfds);
    FD_SET(fileno(stdin), &rfds);

   /* Wait up to five seconds. */
    tv.tv_sec = 5;
    tv.tv_usec = 0;

   retval = select(1, &rfds, NULL, NULL, &tv);
    /* Don't rely on the value of tv now! */

   if (retval == -1) {

        perror("select()");

   }
   else if (retval) {

        printf("Data is available now.\n");
        if(read(fileno(stdin), &char, 1) != 1){

           printf("Errore di lettura\n");

        }

    }
    else {

        printf("No data within five seconds.\n");

    }

   return 0;
}
Dovrebbe leggere un byte dallo stdin, ma non ne sono sicuro.