From: Derek Lewis <lewisd@...00f.net>
Date: 2003-12-13T02:21:07+09:00
Subject: Bug with fifos in Linux?


I don't know if this is a new bug, known bug, or some sort of feature...
When I try to open a fifo, the entire ruby interpreter locks until
something else opens the other "end" of the fifo.  Here's some example
code:

FIFO_FILE='/tmp/rubyfifo'
`mkfifo "#{FIFO_FILE}"` unless test(?e, FIFO_FILE)

thread = Thread.new {
   puts "Opening fifo for writing"
   File.open(FIFO_FILE, 'w') { |file|
      puts "Starting write loop"
      while true
         puts "Thread is running"
         sleep 1
         file.puts "Thread is running"
      end
   }
}

puts "Opening fifo for reading"
File.open(FIFO_FILE, 'r') { |file|
   puts "Reading from fifo"
   file.each_line { |line|

      puts "Read from fifo: #{line}"
   }
}


The only output I see from this is "Opening fifo for writing".
If the thread is changed to:

thread = Thread.new {
   puts "Starting loop"
   while true
      puts "Thread is running"
      sleep 1
   end
}


Then instead, I see this output:
Starting loop
Thread is running
Opening fifo for reading

And I don't see "Thread is running" until I execute this in another
shell:

cat > /tmp/rubyfifo

As soon as I close the cat, the ruby program exits nicely.


Derek Lewis

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