Driver-tutorial/select_poll/multi2.c

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <fcntl.h>
#include <stdlib.h>

int main(){

    int fd1, fd2;
    fd_set read_set, write_set;
    char buf[10];
    struct timeval timeout;
    int n;

    timeout.tv_sec = 10;
    fd1 = open("./pone", O_RDWR);
    fd2 = open("./ptwo", O_RDWR);

    FD_ZERO(&read_set);
    FD_SET(fd1, &read_set);
    FD_SET(fd2, &read_set);

    n = select(FD_SETSIZE, &read_set, NULL, NULL, &timeout);
    if( n < 0 ){
        perror("select ");
        exit(1);
    }

    // test whether fd1 is ready or not
    if( FD_ISSET(fd1, &read_set) ){
        printf(" reading from fd1 (pone)\n");
        n = read(fd1, buf, 10);
        printf(" read data = %s from pone \n", buf);
    }

    // test whether fd2 is ready or not
    if( FD_ISSET(fd2, &read_set) ){
        printf(" reading from fd2 (ptwo)\n");
        n = read(fd2, buf, 10);
        printf(" read data = %s from ptwo \n", buf);
    }
    
    return 0;

}