Bug #20461
Updated by yamam (Masanari Yamamoto) 2 months ago
When executing the following script, pipe_r is not supposed to be readable because no writing is done to pipe_w, but pipe_r is included in the return value rs of IO.select. Since it is not possible to read from pipe_r, the IO::EAGAINWaitReadable exception is raised.
```ruby
pipe_r, pipe_w = IO.pipe
1000.times do |i|
IO.popen(['seq', File.popen(['seq', '1', '1000']) do |popen_r|
j = 0
while true
rs, ws, = IO.select([popen_r, pipe_r])
if rs.include?(popen_r)
unless popen_r.gets
break
end
end
if rs.include?(pipe_r)
puts "IO.select BUG pipe_r is not readable! i = #{i} j = #{j}"
p pipe_r.read_nonblock(1)
end
j += 1
end
end
end
```
```
$ ruby select.rb
IO.select BUG pipe_r is not readable! i = 0 j = 20
<internal:io>:63:in `read_nonblock': Resource temporarily unavailable - read would block (IO::EAGAINWaitReadable)
from select.rb:14:in `block (2 levels) in <main>'
from select.rb:3:in `popen'
from select.rb:3:in `block in <main>'
from select.rb:2:in `times'
from select.rb:2:in `<main>'
[1] 73732 exit 1 ruby select.rb
```