[Expectperl-discuss] Can use Expect to spawn a process with stdin, stdout?

[Jerry K. <je...@ie...>]

Markdown.pl is a Perl text-processing filter which takes input from stdin and
outputs to stdout.  I'd like to call it as a child process from within my
script -- pass it a string and get a string back.

My first attempt is to use open2(), but after failing and reading perldoc
perlipc carefully I realized my problem is that, like most programs,
Markdown.pl does not support "unbuffered" I/O.  Advice in perldoc perlipc
suggests using 'Expect'  module.  

So, I try this code: 

#!/usr/bin/perl 
use Expect ; 
my $stdin = "*Hello* **World**\n" ; 
my $cmd = '/Users/jk/Downloads/Markdown_1.0.1/Markdown.pl'; 
my @parameters = () ;  # No arguments to Markdown.pl 
my $exp = new Expect; 
$exp->raw_pty(1); 
$exp->spawn($cmd, @parameters) 
    or die "Cannot spawn $command: $!\n"; 
$exp->send($stdin); 
print "Waiting for output.\n" ; 
my $stdout = $exp->expect(undef); 
print "stdout: $stdout\n" ; 

The result is "Waiting for output" -- forever.  If I give the expect()
function a timeout parameter, then it times out after the given time, but
returns no data. 

Does anyone know how to use the Expect module in the simple case of spawning
a command with stdin to get stdout?

Maybe this is not appropriate.  Although perldoc peripc recommends Expect
for this problem, Expect documentation poo-poos such a usage:
  Question: "I just want to read the output of a process without 
              expect()ing anything. How can I do this?" 
    Answer: "[ Are you sure you need Expect for this? How about qx() or
open("prog|")? ] 

That's what we call "the runaround".  Should I give up and write my stdin to
a temporary file?  I know I can make that work but at this point curiosity
and the need for closure has taken over ;)
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