# Goblin (suspendable) ports & O\_NONBLOCK **URL:** \ **Category:** Spritely Goblins\ **Created:** [August 11, 2026, 2:01am UTC](https://community.spritely.institute/t/goblin-suspendable-ports-o-nonblock/846 "2026-08-11T02:01:50Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![spacebarista](https://avatars.discourse-cdn.com/v4/letter/s/b487fb/32.png) [@spacebarista](https://community.spritely.institute/u/spacebarista)\ **Post date:** [August 11, 2026, 2:01am UTC](https://community.spritely.institute/t/goblin-suspendable-ports-o-nonblock/846/1 "2026-08-11T02:01:50Z")
Hello, Goblins is using fibers as far as I understand. Fibers says that `O_NONBLOCK` should be set to every file descriptor being read or written to, for a fiber to correctly suspend. The Guile manual on the other hand says that `(ice-9 suspendable-ports)` may be used for IO that suspends (to prompt) instead of blocking. Can you please clarify what the correct order of doing things is? Should I use both `O_NONBLOCK` and suspendable ports together? I don’t see either fibers nor goblin use `install-suspendable-ports!`, except in `tests/repl-driver.scm`. I don’t understand how `^io` works without using `O_NONBLOCK`. On the other hand, all the test I see in goblins that uses `O_NONBLOCK` relates to sockets; but what about the current input/output/error ports? For example, in an ncurses UI program, which is what I’m doing now… Since Guile does not seem to use `O_NONBLOCK` in the Scheme source code of `(ice-9 suspendable-ports)` and since it does require a C shim as well, I assume that it’s the C-side that sets up `O_NONBLOCK` on stdin/stdout/stderr. So perhaps that suffices? But then, why is goblins not using suspendable-ports in `^io`? **Edit:** I believe that the answer is coming from “Non-Blocking I/O” in the Guile manual, but essentially it is this: 1. Use `(ice-9 suspendable-ports)` and call `(install-suspendable-ports)`. 2. Set `O_NONBLOCK` to current input/output/error (if desired) and to every subsequent port you open. 3. Now you can use `^io` with them and/or fibers. I think this should be documented a bit more carefully in the `^io` page, is there a reason why it’s not? I can only guess that maybe the hope was that goblins would support more than the fibers scheduler? **Edit 2:** The Guile manual on non-blocking I/O also mentions at the end that Guile does not currently include an implementation of the facility to suspend the current thread, and links to [8sync](https://gnu.org/software/8sync), has that been superseded by Fibers? I see the latest commit is from 2021. I wonder if the Guile manual should be changed in that section? @cwebber **Edit 3:** Apparently I should have ncurses I/O in a dedicated thread because it wouldn’t work right with `O_NONBLOCK` on stdin; or I need to figure out an alternative to correctly suspend. A bit overwhelming right now, I would appreciate all hints. ---
**Author:** ![dthompson](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.spritely.institute/dthompson/32/95_2.png) [@dthompson](https://community.spritely.institute/u/dthompson)\ **Post date:** [August 11, 2026, 1:10pm UTC](https://community.spritely.institute/t/goblin-suspendable-ports-o-nonblock/846/2 "2026-08-11T13:10:22Z")
Hi, I’ll try to unpack this a bit. First, regarding `(ice-9 suspendable-ports)` and `install-suspendable-ports!`, this is taken care of by [fibers](https://codeberg.org/guile/fibers/src/branch/main/fibers.scm#L135) so users of fibers (you and I) don’t have to worry about it. Next, even with suspendable ports activated, the `O_NONBLOCK` flag still needs to be set on file descriptors that you are managing yourself since that is a low-level interface and Guile doesn’t implicitly set any flags for you. I’m not 100% sure but I think this applies to stdin/stdout, as well. I think that the `^io` docs could be improved with more examples since integrating actors with fibers has a number of subtleties. It is important that you perform port I/O from something like `^io` otherwise you run the risk of suspending a vat’s fiber and breaking your Goblins program. And yes, the Guile manual is out-of-date. It should recommend fibers instead. Hope this has helped clear things up somewhat! ---
**Author:** ![spacebarista](https://avatars.discourse-cdn.com/v4/letter/s/b487fb/32.png) [@spacebarista](https://community.spritely.institute/u/spacebarista)\ **Post date:** [August 11, 2026, 3:27pm UTC](https://community.spritely.institute/t/goblin-suspendable-ports-o-nonblock/846/3 "2026-08-11T15:27:02Z")
Thanks for clarifying! I’ll try to update some of the docs and proceed with your advice. As for stdin/stdout, yes you’re right except that with ncurses there’s some issues and it’s probably safest to run it on its own thread without `O_NONBLOCK`.