我们如何知道对 epoll_wait() 的调用是边沿触发还是电平触发？

Question

我知道指定事件EPOLLETswitches epoll 从水平触发到边缘触发。 这是否意味着默认调用epoll_wait() 是级别触发的？

Answer 1

见http://man7.org/linux/man-pages/man7/epoll.7.html

By contrast, when used as a level-triggered interface (the default,
when EPOLLET is not specified), epoll is simply a faster poll(2), and
can be used wherever the latter is used since it shares the same
semantics.

所以，当没有指定 EPOLLET 时，level-triggered 是默认选项。