---
name: "io_wait"
section: "3"
platform: "linux"
package: "libowfat-dev"
version: "0.32-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/io_wait"
---

# io\_wait(3)

wait for events

## NAME

io\_wait - wait for events

## SYNTAX

**#include \<libowfat/io.h\>**

void **io\_wait**();

## DESCRIPTION

io\_wait() checks the descriptors that the program is interested in to see whether any of them are ready. If none of them are ready, io\_wait() tries to pause until one of them is ready, so that it does not take time away from other programs running on the same computer.

io\_wait pays attention to timeouts: if a descriptor reaches its timeout, and the program is interested in reading or writing that descriptor, io\_wait will return promptly.

Under some circumstances, io\_wait will return even though no interesting descriptors are ready. Do not assume that a descriptor is ready merely because io\_wait has returned.

io\_wait is not interrupted by the delivery of a signal. Programs that expect interruption are unreliable: they will block if the same signal is delivered a moment before io\_wait. The correct way to handle signals is with the self-pipe trick.

## NOTE

Depending on the underlying operating system primitive, there is a potential race condition to be aware of. Some event notification mechanisms (for example, kqueue on BSD and epoll on Linux) will return multiple events. If your application operates on pairs of file descriptors (a proxy server maybe), and an error on one descriptor can lead to closing the other descriptor, then an outstanding event on the other descriptor can still be queued for delivery to you. Be prepared to receive events for a descriptor that has already been closed.

## SEE ALSO

[io\_waituntil(3)](/io_waituntil/3.md), [io\_check(3)](/io_check/3.md), [io\_wantread(3)](/io_wantread/3.md), [io\_wantwrite(3)](/io_wantwrite/3.md), [io\_fd(3)](/io_fd/3.md)