文件I/O 互斥操作 select

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>

int main()
{
    int fds[2];
    char buf[7];
    int i, rc, maxfd;
    fd_set inset1, inset2;
    struct timeval tv;
    
    if((fds[0]=open("hello1", O_RDWR|O_CREAT, 0666))<0)
        perror("open hello1 err");
    if((fds[1]=open("hello2", O_RDWR|O_CREAT, 0666))<0)
        perror("open hello2 err");
    if((rc=write(fds[0], "Hello!\n", 7)))
        printf("rc=%d\n", rc);
    lseek(fds[0], 0, SEEK_SET);
    maxfd = fds[0]>fds[1]?fds[0]:fds[1];
    FD_ZERO(&inset1);
    FD_SET(fds[0], &inset1);
    
    
    FD_ZERO(&inset2);
    FD_SET(fds[1], &inset2);
    
    tv.tv_sec=2;
    tv.tv_usec=0;
	int  j;
    while(FD_ISSET(fds[0], &inset1)||FD_ISSET(fds[1], &inset2))
    {
        if(select(maxfd+1, &inset1, &inset2, NULL, &tv)<0)
            perror("select");
        else{
            if(FD_ISSET(fds[0], &inset1)){
                rc = read(fds[0], buf, 7);
//                printf("rc %d\n", rc);
                if(rc>0){
                      buf[rc]='\0';
//                    for(j=0; j<7; j++)
//                    {
//                        printf("buf [%d] = %c\n", j, buf[j]);
//                    }
                    printf("=====>> rc=%d, read: %s\n", rc, buf);
                }
                else
                    perror("read err");
            }
            if(FD_ISSET(fds[1], &inset2)){
                rc = write(fds[1], buf, 7);
                if(rc>0){
                    buf[rc] = '\0';
                    printf("rc=%d, write: %s\n", rc, buf);
                }
                else
                    perror("write err");
                usleep(1000000);
            }
        }
    }
    return 0;
}