阻塞与非阻塞

阻塞的概念

read函数在读设备或者读管道,或者读网络的时候,

设置非阻塞

#include <stdio.h>
    2 #include <unistd.h>
    3 #include <stdlib.h>
    4 #include <fcntl.h>
    5 #include <string.h>
    6 #include <sys/types.h>
    7 
    8 
✹   9 int main(int argc, char *argv[])
   10 {
   11     // int fd = open("/dev/tty", O_RDWR | O_NONBLOCK);
   12     int fd = open("dev/tty", O_RDWR);
   13     // fcntl() 函数   设置非阻塞
   14     int flags =  fcntl(fd, F_GETFL);
   15     flags |= O_NONBLOCK;
   16     fcntl(fd, F_SETFL, flags);
   17                                                                                                                                                                                                                                                                         
   18     char buf[256];
   19     int ret = 0;
   20     while (1)
   21     {
   22         ret = read(fd, buf, sizeof(buf));
   23         if (ret < 0)
   24         {
   25             perror("read err:");
   26             printf("ret is %d\n", ret);
   27         }
   28         if (ret)
   29         {
   30             printf("buf is %s\n", buf);
   31         }
   32         printf("haha\n");
   33         sleep(1);
   34     }
   35     close(fd);
   36     return 0;
   37 }