Which Ruby is in use?

[Hassan Schroeder]

Is there a way to tell from within a program which executable is being
used -- which executable, not the version -- to run it?

Seems like there should be, but I'm striking out...

TIA,

 

[Hassan Schroeder]

On Tue, Jul 27, 2010 at 2:20 PM, Joseph E. Savard

As I said, I'm not interested in the version, just the path to the executable.

puts "And finally the ruby executable #{ENV['_']}"

Doesn't appear to work in JRuby. Do you know if it works in anything
else besides MRI?

 

[Joel VanderWerf]

On Tue, Jul 27, 2010 at 2:20 PM, Joseph E. Savard

As I said, I'm not interested in the version, just the path to the executable.

puts "And finally the ruby executable #{ENV['_']}"

Doesn't appear to work in JRuby. Do you know if it works in anything
else besides MRI?

Maybe this will work?
=> "/usr/local/bin/ruby"

 

[Hassan Schroeder]

Maybe this will work?

=> "/usr/local/bin/ruby"

Works in a Rails console, but not a Ruby program. But thanks, now
that I consider it I should be able to work with that

 

[Joel VanderWerf]

Works in a Rails console, but not a Ruby program. But thanks, now
that I consider it I should be able to work with that

Hm, that's surprising. I tested it in ruby and jruby programs. What's
the problem?

$ ruby -v -rrbconfig -e 'p File.join(*Config::CONFIG.values_at("bindir",
"ruby_install_name"))'
ruby 1.8.7 (2010-06-23 patchlevel 299) [x86_64-linux]
"/usr/local/bin/ruby"

$ ruby19 -v -rrbconfig -e 'p
File.join(*Config::CONFIG.values_at("bindir", "ruby_install_name"))'
ruby 1.9.2dev (2010-07-02 revision 28524) [x86_64-linux]
"/usr/local/bin/ruby19"

$ jruby -v -rrbconfig -e 'p
File.join(*Config::CONFIG.values_at("bindir", "ruby_install_name"))'
jruby 1.5.0 (ruby 1.8.7 patchlevel 249) (2010-05-12 6769999) (Java
HotSpot(TM) 64-Bit Server VM 1.6.0_20) [amd64-java]
"/usr/local/jruby/bin/jruby"

 

[Hassan Schroeder]

Hm, that's surprising. I tested it in ruby and jruby programs. What's the
problem?

ripple:~$ cat foo.rb
puts File.join *Config::CONFIG.values_at("bindir", "ruby_install_name")
ripple:~$ ruby foo.rb
foo.rb:1: uninitialized constant Config (NameError)
ripple:~$ jruby foo.rb
foo.rb:1: uninitialized constant Config (NameError)
ripple:~$

--=20
Hassan Schroeder ------------------------ (e-mail address removed)
twitter: @hassan

 

[Joel VanderWerf]

ripple:~$ cat foo.rb
puts File.join *Config::CONFIG.values_at("bindir", "ruby_install_name")
ripple:~$ ruby foo.rb
foo.rb:1: uninitialized constant Config (NameError)
ripple:~$ jruby foo.rb
foo.rb:1: uninitialized constant Config (NameError)
ripple:~$

You must require 'rbconfig':

$ ruby -v -rrbconfig -e 'p File.join(*Config::CONFIG.values_at("bindir",
"ruby_install_name"))'
ruby 1.8.7 (2010-06-23 patchlevel 299) [x86_64-linux]
"/usr/local/bin/ruby"

 

[Hassan Schroeder]

You must require 'rbconfig':

Yes, I see that -- my first thought was that that's not going to be practical
in this case, but thanks, I'll play around with it.

 

[Fabian Marin]

hope I did not misunderstand the question, but would this work??

%x{which $0}

It seems too easy to work so I probably missed something

 

[Hassan Schroeder]

hope I did not misunderstand the question, but would this work??

%x{which $0}

It seems too easy to work so I probably missed something

Thanks, but
$ irb=> "/bin/sh\n"

isn't what I was looking for

 

[Edward Middleton]

Thanks, but
$ irb
=> "/bin/sh\n"

isn't what I was looking for

Thats because the $0 is being evaluated by the shell not ruby. What you
actually want is %x{which #{$0}} which will give "which irb" to the
shell. If the PATH environment is the same this should give you the
full path.

Edward

 

[Fabian Marin]

Thats because the $0 is being evaluated by the shell not ruby. What you
actually want is %x{which #{$0}} which will give "which irb" to the
shell. If the PATH environment is the same this should give you the
full path.

Edward

Yeah I missed that. I could not execute/test the code I suggested
because I'm using Win XP right now, sigh...

Edward, you're right. Once $0 is evaluated by Ruby that should work in
a Unix environment.

 

[Caleb Clausen]

Edward, you're right. Once $0 is evaluated by Ruby that should work in
a Unix environment.

But watch:

$ ruby -e 'p $0'
"-e"

That doesn't seem to helpful. Hassan seemed to want the path to the
ruby interpreter, not the path to the ruby script it's executing.

Hassan, what is you objection to using rbconfig.rb as Joel suggests?
AFAIK, that's the best (only real) solution to this particular
problem.

 

[Roger Pack]

Is there a way to tell from within a program which executable is being
used -- which executable, not the version -- to run it?

os gem:
=> "c:/installs/ruby192-rc1/bin/ruby.exe"

Or
require 'rubygems'

Gem.ruby

I believe.
Or apparently ENV['_'] thanks Caleb.
-r
-r

 

[Hassan Schroeder]

Hassan, what is you objection to using rbconfig.rb as Joel suggests?
AFAIK, that's the best (only real) solution to this particular
problem.

Yeah, that's the pick of the litter. I was looking for the minimal solution
and it seemed unDRY to have to require that everywhere I might need
the information, but -- undercaffeinated premature optimization aside --
since my real current use case only requires patching one (Rails app)
plugin it's fine.

I haven't checked yet whether there's a bug filed against JRuby for
the lack of support for ENV['_'], which obviously wins the minimalist
contest

Thanks everyone for the suggestions!

 

[Roger Pack]

I haven't checked yet whether there's a bug filed against JRuby for
the lack of support for ENV['_'], which obviously wins the minimalist
contest

ENV['_']
doesn't seem to work for me on windows at all:

ENV['_']

=> nil

Thought it might still be a bug in jruby that it not have one under
linux, I'm not entirely sure.
-r

 

[Caleb Clausen]

I haven't checked yet whether there's a bug filed against JRuby for
the lack of support for ENV['_'], which obviously wins the minimalist
contest

ENV['_']
doesn't seem to work for me on windows at all:

ENV['_']

=> nil

Thought it might still be a bug in jruby that it not have one under
linux, I'm not entirely sure.

I just did a quick check, and I'm not seeing anywhere in the ruby
source where it sets an envvar named _. Perhaps this envvar is a
feature of bash or linux or something other than ruby.

 

[Joel VanderWerf]

I haven't checked yet whether there's a bug filed against JRuby
for the lack of support for ENV['_'], which obviously wins the
minimalist contest

ENV['_'] doesn't seem to work for me on windows at all:

ENV['_']

=> nil

Thought it might still be a bug in jruby that it not have one under
linux, I'm not entirely sure.

I just did a quick check, and I'm not seeing anywhere in the ruby
source where it sets an envvar named _. Perhaps this envvar is a
feature of bash or linux or something other than ruby.

Yeah, I think it's just a shell feature:

$ ruby -e 'p ENV["_"]'
"/usr/local/bin/ruby"
$ env ruby -e 'p ENV["_"]'
"/usr/bin/env"

That's the behavior in both zsh and bash.

Found this in some bash docs:

 

[Hassan Schroeder]

That's the behavior in both zsh and bash.

Ah, good detectorizing and that explains the JRuby "issue" -- even
though $JRUBY_HOME/bin/jruby is a bash script, it contains this line:

JRUBY_SHELL=/bin/sh

so apparently no '_' environment variable will be forthcoming.

Ya learn something every day!