Bug #21495: IO.read_nonblock does not work under a rescue IO::TimeoutError

• Status: Open
• Assignee: -
• Target version: -
• ruby -v: ruby 3.2.8 (2025-03-26 revision 13f495dc2c) [x86_64-linux]
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[dE (dE Techno)]

In this particular code --

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

[dE (dE Techno)]

• ruby -v changed from de@myworkstation ~/docs/Practice/Software/ruby $ ruby -v ruby 3.2.8 (2025-03-26 revision 13f495dc2c) [x86_64-linux] to ruby -v ruby 3.2.8 (2025-03-26 revision 13f495dc2c) [x86_64-linux]

[dE (dE Techno)]

• ruby -v changed from ruby -v ruby 3.2.8 (2025-03-26 revision 13f495dc2c) [x86_64-linux] to ruby 3.2.8 (2025-03-26 revision 13f495dc2c) [x86_64-linux]