#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <sys/select.h>


char buf[1024];


int main(){
    int fd[2];
    int result;
    int acc = 0;

    int the_end = 0;
    fd_set rd_set;

    fd[0] = open("./in1", O_RDONLY | O_NONBLOCK);
    fd[1] = open("./in2", O_RDONLY | O_NONBLOCK);
    if(fd[0] == -1){
        printf("%sn", strerror(errno));
        exit(EXIT_FAILURE);
    }
    if(fd[1] == -1){
        printf("%sn",strerror(errno));
        exit(EXIT_FAILURE);
    }

    while(1){
        FD_ZERO(&rd_set);
        FD_SET(fd[0], &rd_set);
        FD_SET(fd[1], &rd_set);
        result = select(fd[1] + 1, &rd_set, NULL, NULL, NULL);
        printf("result = %dn", result);
        if(result == -1){
            printf("%sn", strerror(errno));
            exit(EXIT_FAILURE);
        }
        if(result){
            if(FD_ISSET(fd[0], &rd_set)){
                result = read(fd[0], buf, 1024);
                if(result == -1){
                    close(fd[0]);
                    the_end++;
                } else if(result != 0) {
                    buf[result] = 0;
                    printf("from 1: %dn", atoi(buf));
                    acc += atoi(buf);
                }
                FD_CLR(fd[0], &rd_set);
            }
            if(FD_ISSET(fd[1], &rd_set)){
                result = read(fd[1], buf, 1024);
                if(result == -1){
                    close(fd[1]);
                    the_end++;
                } else if(result != 0) {
                    buf[result] = 0;
                    printf("from 2: %dn", atoi(buf));
                    acc += atoi(buf);
                }
                FD_CLR(fd[1], &rd_set);
            }
        }
        result = 0;
        if(the_end == 2){
            break;
        }

    }
    printf("%dn", acc);
    return 0;
}

fd[0] = open("./in1", O_RDONLY | O_NONBLOCK);
fd[1] = open("./in2", O_RDONLY | O_NONBLOCK);