From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-08-06T12:11:07+09:00
Subject: Re: interactively processing a line at a time

On Sat, 6 Aug 2005, Forrest Chang wrote:

> HI All:
>
>        For the following code segement running on win32 ruby (1 click installer)
>
> sout = IO.popen( "output");
> while( line = sout.gets)
>  do_something_with( line)
> end
>
>
>        If for example, "output" printed out something 5 times every second,
> then on the command line, I would see something printed out every
> second, 5 times.  Running through the above code, I would not see
> anything until after 5 secs, which I assume that after the program
> exits, the output is flushed, and then it would be all 5 entries.  I
> ran the same sort of code successfully solaris, so I expected it to
> work on windows.
>
>        I did an experiment, and wrote a ruby program that printed a
> line then flushed STDOUT, paused, repeated, etc., and it works as
> suspected.  Since I do not have control over the actual "output"
> program, how can I get it so that each line is flushed? sout.sync =
> true didn't work (I imagine it only works if I write to sout)
>
>        Any ideas?

try this - it should/might work on windoze - i assume it inherits open file
handles from the parent.  i ran it on xp and it seemed fine:

     harp:~ > ruby a.rb
     [Fri Aug 05 20:49:51 MDT 2005, "42\n"]
     [Fri Aug 05 20:49:56 MDT 2005, "42\n"]
     [Fri Aug 05 20:50:01 MDT 2005, "42\n"]
     [Fri Aug 05 20:50:06 MDT 2005, "42\n"]
     [Fri Aug 05 20:50:11 MDT 2005, "42\n"]
     ...
     ...
     ...


     harp:~ > cat a.rb
     require 'tempfile'

     def popen_sync cmd
       tf = Tempfile::new $PROGRAM_NAME
       tf.puts <<-ruby_code
         STDOUT.sync = true
         exec STDIN.read
       ruby_code
       tf.close

       sync_cmd = "ruby #{ tf.path }"
       pipe = IO::popen sync_cmd, 'r+'
       pipe.puts cmd
       pipe.close_write
       pipe
     end

     output = "ruby -e 'loop{ p 42; sleep 5}'"
     sout = popen_sync output

     while(line = sout.gets)
      p [Time::now, line]
      STDOUT.flush
     end


again - this will only work if exce inherits open files and there properties...

hth.

-a
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