C/C++ open函数的阻塞和非阻塞
C/C++ open函数的阻塞和非阻塞
调用open函数时,可以指定是以阻塞方式还是以非阻塞方式打开一个文件描述符。
- 阻塞方式打开:
int fd = open("/dev/tty", O_RDWR|O_NONBLOCK);
- 非阻塞方式打开:
int fd = open("/dev/tty", O_RDWR);
例子:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
int main(int argc, char* argv[]){
int fd = open("/dev/tty", O_RDWR|O_NONBLOCK);
char buf[256];
while(1){
int ret = read(fd, buf, sizeof buf);
if(ret < 0){
perror("read:");
printf("ret :%d\n", ret);
}
printf("buf is:%s", buf);
printf("haha\n");
}
}
除了使用【O_NONBLOCK】外,还可以使用fcntl函数,原型如下:
#include <unistd.h>
#include <fcntl.h>
int fcntl(int fd, int cmd, ... /* arg */ );
F_GETFD (void)
Return (as the function result) the file descriptor flags; arg
is ignored.
F_SETFD (int)
Set the file descriptor flags to the value specified by arg.
例子:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
int main(int argc, char* argv[]){
int fd = open("/dev/tty", O_RDWR);
//先取得fd的flag
int flags = fcntl(fd, F_GETFL);
//再在原来fd的flag的基础上,设置上O_NONBLOCK
flags |= O_NONBLOCK;
//让新的flag生效
fcntl(fd, F_SETFL, flags);
char buf[256];
while(1){
int ret = read(fd, buf, sizeof buf);
if(ret < 0){
perror("read:");
printf("ret :%d\n", ret);
}
printf("buf is:%s", buf);
printf("haha\n");
sleep(1);
}
}
linuxboy的RSS地址:https://www.linuxboy.net/rssFeed.aspx
本文永久更新链接地址:https://www.linuxboy.net/Linux/2019-04/158300.htm
评论暂时关闭