Execute Ruby Script

Hi there,

i’m wondering if it’s possible to execute a external Ruby-Script via
Rails.

It is my aim to scan my hard-disc with this script, returning values (my
directory-structure) to rails.

Can anyone give me a hint?

On Tue, Jul 14, 2009 at 1:49 AM, Hans H. <
[email protected]> wrote:

Hi there,

i’m wondering if it’s possible to execute a external Ruby-Script via
Rails.

It is my aim to scan my hard-disc with this script, returning values (my
directory-structure) to rails.

Can anyone give me a hint?

Yes, it’s possible to execute a Ruby script from Rails. Please remember
that Rails is implemented in Ruby and you can use an method called
‘system’.

Good luck,

-Conrad

Hi there,

now i tried to execute via System-Command but i just can catch the value
true/false.

Is it possible to declare a global variable in my ruby script - execute
the script - and then catch it with rails?

Greetz
Hans

On Tue, Jul 14, 2009 at 3:04 AM, Hans H. <
[email protected]> wrote:

Hi there,

now i tried to execute via System-Command but i just can catch the value
true/false.

Are you doing something like this?

exit_status = system( <some_command>)

Is it possible to declare a global variable in my ruby script - execute
the script - and then catch it with rails?

Yes, it’s possible to declare a global variable within your script. I
would
recommend getting yourself a copy of “Programming Ruby” as a desk-side
reference.

Good luck,

-Conrad

Conrad T. wrote:
[…]

Yes, it’s possible to execute a Ruby script from Rails. Please remember
that Rails is implemented in Ruby and you can use an method called
‘system’.

If the external script is in Ruby, then it probably makes more sense to
use require and load it as part of the Rails app, rather than using
system to call it. You’ll get better integration and not have to spawn
a separate shell.

Good luck,

-Conrad

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

I try and try…
but I can’t make the script be executed (nor an other Programm)
Can someone give me an example to execute external files with rails? So
I can get an idea of the path-description.

Thx a lot

James B. wrote:
[…]

What you are looking for is the backtick ‘`’ method of Kernel, aliased
as %x().
[…]

This shells out just like system() does. It’s a good general method of
running arbitrary shell scripts in other languages, but it should not be
necessary when the scripts are in Ruby. Integrate instead of shelling
out.

[…]

To run one Ruby script from
another your would have something that looked like this, more or less.

caller.rb
#!/usr/bin/env ruby

call the other script and open an new shell

%x(path/to/my/other/script.rb)

No. You’d be better off using require or similar.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

On Jul 14, 7:31 am, Hans H. [email protected]
wrote:

I try and try…
but I can’t make the script be executed (nor an other Programm)
Can someone give me an example to execute external files with rails? So
I can get an idea of the path-description.

Thx a lot

Posted viahttp://www.ruby-forum.com/.

What you are looking for is the backtick ‘`’ method of Kernel, aliased
as %x(). You should refer to the official api at
http://ruby-doc.org/core/
and read this carefully.

Rails is a framework not a programming language. So it is really a
default directory layout supported by a vast amount of clever code to
do most of the grunt work required to write web apps. As other have
pointed out, Ruby is the language used. To run one Ruby script from
another your would have something that looked like this, more or less.

caller.rb
#!/usr/bin/env ruby

call the other script and open an new shell

%x(path/to/my/other/script.rb)
#eof

script.rb
#!/usr/bin/env ruby
puts “script.rb has been called”
#eof

Now, this will display nothing because the stdout of the target script
is not looked for in the calling script, which is the one you ahve
open in your console. So:

caller.rb
#!/usr/bin/env ruby

call the other script and open an new shell

my_stdout = %x(path/to/my/other/script.rb)
puts my_stdout
#eof

That should display the output of script.rb on the console running
caller.rb. script.rb’s stderr can be redirected as well:

caller.rb
#!/usr/bin/env ruby

call the other script and open an new shell

my_stdout = %x(path/to/my/other/script.rb 2> &1)
puts my_stdout
#eof

HTH

Marnen Laibow-Koser wrote:

James B. wrote:

No. You’d be better off using require or similar.

That really depends upon the question being asked. The OP explicitly
asked on how to run an external script, that happened to be written in
Ruby; not, what is the best way to run arbitrary external ruby code from
inside a running Ruby script?

If the latter case then I suggest that the OP consider this approach,
which was recently shown to me by Matt W. on the Cucumber list:

First, write the script and encapsulate its entire code within an
execute method contained in a Script class file. Like so:

script.rb
class Script # should be the actual name of the script.
def initialize(argv) # receive the ARGV array from the calling
process
@argv = argv
end
def execute
# if required then parse any command line arguments in @argv here
puts “script.rb called”
end
end
#eof

If a stand-alone script initiation is required, as with cron say, then
write a stub script that calls the script class and executes the script
code like so:

runner.rb
#!/usr/bin/env ruby
require ‘script’

Script.new(ARGV).execute
#eof

If the encapsulated script is complex enough that it contains its own
internal classes then the whole can be encapsulated inside an outer
class given the script name. The inner class containing the execute
method is then renamed to something like Main. In this case the call
becomes:

Script::Main.new(ARGV).execute

And the class file script.rb has this structure

class Script

class Main
def initialize(argv)
@argv = argv
end
def execute
script code goes here
end
end

class OtherClass

end
end

One may now use the script within any other ruby process as you suggest,
via a simple require and subsequent instantiation. I found this
technique extremely valuable in testing since out of process scripts did
not share the dbms state with the the test harness.

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