0
考虑下面的情况后：TTY事件epoll的队列闭FD 0
- 一个EPOLLIN事件被注册用于FD 0（标准输入）
- 用于FD 0则生成EPOLLIN事件和隐式排队读epoll的内
- FD 0之前闭合（并且EPOLL_CTL_DELeted）调用epoll_wait（）
- epoll_wait（）被调用以读取排队的事件
目前：
- 如果标准输入是一个终端，当epoll_wait（）被调用时，从步骤2 EPOLLIN事件将被报告
- 如果标准输入不是终端，但管道，从EPOLLIN事件第2步将不是被举报
为什么tty案件不同？
测试程序：
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/epoll.h>
struct epoll_event event1 = {
.events = EPOLLIN,
.data = { .fd = 0}
};
int main(int argc, char **argv)
{
int epfd = epoll_create(1);
int rc;
epoll_ctl(epfd, EPOLL_CTL_ADD, 0, &event1);
sleep(2); //allow meself time to type false\n
printf("closing stdin ...\n");
close(0);
//even if i remove it explicitly the event will be found in the que after
epoll_ctl(epfd, EPOLL_CTL_DEL, 0, &event1);
printf("gathering events ...\n");
event1.events = 0;
event1.data.fd = -1;
rc = epoll_wait(epfd, &event1, 1, 0);
switch(rc) {
case 1:
printf("event received: event=%d on fd %d\n", event1.events, event1.data.fd);
break;
case 0:
printf("no events received");
break;
case -1:
printf("epoll_wait error\n");
break;
default:
printf("weird event count %d\n", rc);
}
return 0;
}
与标准输入从TTY运行程序：
[[email protected] src]# ./epolltest
false
closing stdin ...
gathering events ...
event received: event=1 on fd 0
[[email protected] src]# false
[[email protected] src]#
从管道与标准输入运行程序：
[[email protected] src]# cat t.sh
#!/bin/bash
echo "bah";
sleep 10;
[[email protected] src]# ./t.sh | ./epolltest
closing stdin ...
gathering events ...
no events received[[email protected] src]#