How can you interact with Perl programs from Ruby?

Question

It's my understanding that there's no "bridge" between Ruby and Perl to let you call into Perl functions directly from Ruby. It's also my understanding that to call a Perl program from Ruby, you simply put it in backticks(i.e. result = `./helloWorld.pl`). However, this doesn't allow interaction with the Perl program(i.e. you can't interact with prompts or provide input). My quesitons are as follows:

Is there any way to provide input to Perl programs from Ruby(aside from arguments)?
Am I wrong that there is no bridge between Ruby and Perl? Interacting with a program's stdin seems like the wrong way to go when navigating prompts, and the programs I'm dealing with are well-designed and have libraries with the appropriate Perl functions in them.

From your comments on the answers, it sounds like you're looking for something that will be able to call methods inside a running Perl program to interact with it directly? — Schwern
– Schwern, Commented Jan 22, 2010 at 3:49
Yes, I want to be able to do something like perlProgram.execMethod('myPerlPethod'), and have the gap(hashes, arrays, strings, numbers, etc.) bridged. — Mike
– Mike, Commented Jan 22, 2010 at 3:51

mob · Accepted Answer · 2010-01-22 18:20:40Z

5

There's the Inline::Ruby module, though I don't have any direct experience with it that I can share.

EDIT: I did try it out last night -- here's the review: Inline::Ruby was last updated in 2002, when v5.6 was the latest stable release. Docs say it has only been tested on Linux; I was trying to use it with v5.10.1 on Cygwin. Got it to build after some hacking of the XS/C code that comes with the module. Passed some unit tests but failed others. Seemed to import Ruby class's into Perl's namespace ok but was less successful importing standalone functions. Summary: if you need a quick and dirty bridge for Perl and Ruby, Inline::Ruby will probably disappoint you. If you have the patience to figure out how to build the module on your system, and to massage your Ruby code to work with the module, you could find it useful.

edited Jan 22, 2010 at 18:20

answered Jan 22, 2010 at 2:00

mob

119k18 gold badges159 silver badges291 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Mike Over a year ago

This is the opposite of what I want to do - I want to run Perl code inside of Ruby.

Alexandr Ciornii Over a year ago

Mike: Inline:: modules usually allow callbacks to Perl code. So you can run your Ruby program from small Perl program.

user198470 · Accepted Answer · 2010-01-26 00:05:50Z

5

Use Ruby's exec()

rubypl.rb

#!/usr/bin/ruby -w

script = 'perlscript.pl'
exec("/usr/bin/perl #{script}")

perlscript.pl

#!/usr/bin/perl -w
use strict;
print "Please enter your name: ";
my $name = <STDIN>;
chop($name);
if ($name eq "")
{
    print "You did not enter a name!\n";
    exit(1);
} else {
    print "Hello there, " . $name . "\n";
    exit(0);
}

answered Jan 26, 2010 at 0:05

user198470

3513 silver badges11 bronze badges

Comments

user240438 · Accepted Answer · 2010-01-22 05:11:32Z

3

perldoc perlipc states:

DESCRIPTION
       The basic IPC facilities of Perl are built out of the good old Unix
       signals, named pipes, pipe opens, the Berkeley socket routines, and
       SysV IPC calls.  Each is used in slightly different situations.

Ruby is capable of operating each of these.

answered Jan 22, 2010 at 5:11

user240438

Comments

Wayne Conrad · Accepted Answer · 2010-01-22 17:07:21Z

3

Here's how ruby can use a python script, interacting with the script's stdin and stdout.

foo.py reads two integers (each on its own line) from standard input, adds them, and writes the result to standard-out. I don't know perl, so be nice to me:

#!/usr/bin/perl

$a = <STDIN>;
$b = <STDIN>;
$c = int($a) + int($b);
print $c;

foo.rb executes foo.py, giving it two numbers to add, getting back the result and printing it:

#!/usr/bin/ruby1.8

a = 1
b = 2
c = IO.popen('./foo.py', 'w+') do |pipe|
  pipe.puts(a)
  pipe.puts(b)
  pipe.close_write
  pipe.read
end
raise "foo.py failed" unless $? != 0
print "#{a} + #{b} = #{c}"    # => 1 + 2 = 3

edited Jan 22, 2010 at 17:07

answered Jan 22, 2010 at 2:41

Wayne Conrad

109k26 gold badges158 silver badges195 bronze badges

Comments

Schwern · Accepted Answer · 2010-01-22 04:01:20Z

What you want doesn't really exist, to my knowledge.

The closest thing to what you want, on a generic level, is XDebug. It turns a process into a little server that will accept debugging commands. This is generally used for debugging and profiling and not as interprocess communication, but its a possibility. I believe ActiveState's Perl can be run as an XDebug server.

Otherwise, you need explicitly program in some sort of side-channel that your Perl program listens to for commands (which is what XDebug does). It can be as simple as opening a socket that reads a string, evals it, encodes the result as YAML (or whatever) and writes it back. A REPL, but on a socket rather than on a terminal.

There are, obviously, security implications which will be left as an exercise for the reader. You also don't want listening to the socket to interrupt the program so you will now need something event-driven or threaded.

Sorry I don't have anything more specific. It would make a great CPAN module.

Randal Schwartz · Accepted Answer · 2010-01-22 01:59:32Z

2

Perl and Ruby both have various "glues". Perl programs using the Expect module can do a lot more than just "wait for output". More likely though, you could communicate with a well-known protocol like HTTP... a Ruby daemon could put up a listener, and Perl could contact it, or vice versa.

But no, you can't just "embed" ruby code into Perl, or vice versa. You've got to run separate processes and communicate somehow.

answered Jan 22, 2010 at 1:59

Randal Schwartz

44.8k4 gold badges51 silver badges83 bronze badges

3 Comments

Mike Over a year ago

I understand that there needs to be glue - but is there software built to handle this? I wouldn't mind using an inter-process mediator, so long as it was written well. (Also, I'd like to forgo writing one if possible.)

Alexandr Ciornii Over a year ago

Inline::Ruby allows running Ruby code inside Perl program. And it allows calling Perl subs too, so it is possible to use Ruby as main language.

brian d foy Over a year ago

You can embed perl into Ruby as well as any other C program. Not that you should want to, but perl is designed to allow that. Going the other way, Perl has the Inline modules.

pierrotlefou · Accepted Answer · 2010-01-22 02:04:47Z

2

Try Open4 . It is not designed specific for interacting with perl but with any program that need input and ouput. I am still learning to use it ,but I feel it might suit your need.

answered Jan 22, 2010 at 2:04

pierrotlefou

41k39 gold badges140 silver badges176 bronze badges

1 Comment

Mike Over a year ago

Hmm, this answers my first question, but I'd still be very nervous about interacting via stdin/stdout.

David Harris · Accepted Answer · 2010-01-22 05:51:02Z

0

You mentioned in one of your comments that you want to run Perl code inside Ruby. This will not work unless you can make the Ruby interpreter understand Perl syntax. Can I get a BNF/yacc/RE for the Perl language? will help you understand the challenges you will face.

answered Jan 22, 2010 at 5:51

David Harris

2,3501 gold badge13 silver badges25 bronze badges

1 Comment

brian d foy Over a year ago

You don't need the Ruby interpreter to understand Perl. You just (just!) need to embed Perl in a C extension for Ruby. :)

Collectives™ on Stack Overflow

How can you interact with Perl programs from Ruby?

8 Answers 8

2 Comments

Comments

Comments

Comments

Comments

3 Comments

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

2 Comments

Comments

Comments

Comments

Comments

3 Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related