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```ocaml
# #require "eio_posix";;
```
```ocaml
open Eio.Std
```
## Closing an FD removes it from the multiplexer
Closing an FD automatically removes it from epoll's set, meaning that you have
to re-add it using `EPOLL_CTL_ADD`, not `EPOLL_CTL_MOD`.
```ocaml
# Eio_posix.run @@ fun _env ->
Switch.run (fun sw ->
let r, w = Eio_unix.pipe sw in
Eio_unix.Fd.use_exn "await_writable" (Eio_unix.Resource.fd w) @@ fun fd ->
Eio_unix.await_writable fd
);
(* [r] and [w] are now closed. We'll likely allocate the same FD numbers the second time.
Check we don't get confused and try to [EPOLL_CTL_MOD] them. *)
Switch.run (fun sw ->
let r, w = Eio_unix.pipe sw in
Eio_unix.Fd.use_exn "await_writable" (Eio_unix.Resource.fd w) @@ fun fd ->
Eio_unix.await_writable fd
);;
- : unit = ()
```
|
