From: "dE (dE Techno) via ruby-core" <ruby-core@...>
Date: 2025-07-01T06:57:16+00:00
Subject: [ruby-core:122636] [Ruby Bug#21495] IO.read_nonblock does not work under a rescue IO::TimeoutError

Issue #21495 has been reported by dE (dE Techno).

----------------------------------------
Bug #21495: IO.read_nonblock does not work under a rescue IO::TimeoutError
https://bugs.ruby-lang.org/issues/21495

* Author: dE (dE Techno)
* Status: Open
* ruby -v: de@myworkstation ~/docs/Practice/Software/ruby $ ruby -v ruby 3.2.8 (2025-03-26 revision 13f495dc2c) [x86_64-linux]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
In this particular code -- 
``` ruby
execArg = 'echo testwrite; sleep 5'
tofuProcess = IO.popen(execArg, 'r')
puts 'executed tofu process.'
tofuProcess.timeout=2
begin
	tofuOut = tofuProcess.read
rescue IO::TimeoutError
	puts 'rescue occured'
	begin
		tofuOut = tofuProcess.read_nonblock(1)
	rescue IO::EAGAINWaitReadable
		puts 'no data in read buffer!'
	end
	tofuProcess.close
	puts 'process closed'
end
```
tofuProcess.read_nonblock(1) must return a character because the underlying process has produced an output. But it raises a IO::EAGAINWaitReadable exception instead which does not happen outside a rescue IO::TimeoutError block



-- 
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