From: Wybo Dekker <wybo@...>
Date: 2005-06-16T19:37:45+09:00
Subject: stubborn program using readline

Hi, 

I've been on the list a few days ago with a readline-problem, for which 
there doesn't seem to be a quick fix. I'm now trying a dirty fix... but 
this seems to be a very stubborn problem.

Here is my original test program

	# rltest - test for readline
	# run me like this: (i.e. operating on a file)
	#
	# ruby rltest rltest
	#
	# and all is fine. But run me like so: (i.e. operating on stdin)
	#
	# ruby rltest < rltest
	#
	# and see that I successfully count my own lines, 
	# then also print the "type return to quit" prompt, 
	# but finally seem to be looping in the readline function, and 
	# can only be stopped with ctrl-C,
	# ( not even with ctrl-D - I'm not looking at the terminal)
	
	require 'readline'
	include Readline
	
	# count lines in stdin (the mail message):
	n=0; while gets: n+=1 end
	puts "#{n} lines"
	
	readline("type return to quit: ")
	puts "quitting..."

I tried to get around this problem by testing if input is from stdin,
and if so, making a temporary copy of stdin and re-running the program
on that copied file:

	file = ARGV.shift || ''
	if file == ''
	   require 'tempfile'
	   f = Tempfile.new('vpp')
	   name = f.path
	   puts "Making temporary file: #{name}"
	   n = 0
	   while gets
	      f.puts
	      n += 1
	   end
	   f.close
	   puts "Wrote #{n} lines"
	   system($0, name)
	else
	   require 'readline'
	   include Readline
	   puts "reading #{file}"
	   # count lines in stdin (the mail message):
	   n = 0
	   open(file).each do 
	      n+=1
	   end
	   puts "Saw #{n} lines"
	
	   readline("type return to quit: ")
	   puts "quitting..."
	end

Running this with: ruby rltest rltest says:

	reading rltest
	Saw 30 lines
	type return to quit: 
	quitting...

But to my astonishment, running with: ruby rltest < rltest stays in a
loop, like the original test program:

	Making temporary file: /data/tmp/vpp19009.0
	Wrote 30 lines
	reading /data/tmp/vpp19009.0
	Saw 30 lines
	type return to quit: 
	./rltest:28:in `readline': Interrupt
	        from ./rltest:28

Can anybody explain this?

-- 
Wybo