RubyGem, find path of installed gem through ruby

Ruby
1

Hey All,

First, where is there some api docs for rubygem related methods and
classes?

Second, I have a gem that bundles some required files for the gem. How
do I find the path of the installed gem, so that I can load the bundled
files. For example, I have one executable file, that needs to load some
files that were included (in the lib) dir. But I do I know what the path
of my gem is?

Thanks all

2

Hey Tom, Thanks, that information is definitely what I’m looking for.
How would I get that info from within a ruby script. Specifically the
“GEM PATH” is what I would need. Is there a method to get that?

thanks.

3

Aaron S. wrote:

Hey All,

First, where is there some api docs for rubygem related methods and
classes?

/usr/lib/ruby/gems/1.8/doc/rubygems-1.3.1/rdoc (Linux - Kubuntu)

Second, I have a gem that bundles some required files for the gem. How
do I find the path of the installed gem, so that I can load the bundled
files. For example, I have one executable file, that needs to load some
files that were included (in the lib) dir. But I do I know what the path
of my gem is?

Thanks all

~$ gen env

–

Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< [email protected] >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)
4

or rather, the “INSTALLATION DIRECTORY.”

5

Aaron S. wrote:

Hey Tom, Thanks, that information is definitely what I’m looking for.
How would I get that info from within a ruby script. Specifically the
“GEM PATH” is what I would need. Is there a method to get that?

or rather, the “INSTALLATION DIRECTORY.”

===========================

If you had any idea how paltry my knowledge of Ruby really is you would
ask me such questions! But…I got us this far, so…

I think I’d try a system call to “gem env”, and put the output in a
string, then locate “INSTALLATION DIRECTORY:” with StringScanner, and
take everything after that, up to the EOL as the path you’re after.
Easy, actually.

Only I’m momentarily stumped as to how to make the system call AND
capture the output. Thomas (Pickaxe 2) says it can be done using
backtics. I tried it in irb and got nothing. Still trying to figure it
out. It’d be a good trick to know.

t.

–

Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< [email protected] >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)
6

Tom C. wrote:

backtics. I tried it in irb and got nothing. Still trying to figure
VERSION: 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]\n -
I leave it to you to get the code to have StringScanner find and
return the path. Somehow I keep thinking regular expressions might be
helpful here, but I dare not there. I think I hear the ice cracking
already.

t.

Also, you might find something useful here:
http://tech.natemurray.com/2007/03/ruby-shell-commands.html

t.

–

Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< [email protected] >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)
7

there should be something that’s part of the rubygem api, so I don’t
have to call system commands. I see where you’re going with the regex on
the gem env command, but there has to be a better way.

8

Tom C. wrote:

If you had any idea how paltry my knowledge of Ruby really is you
out. It’d be a good trick to know.

t.

Bummer. In order to preserve my reputation, I managed to get irb a bit
hung up, so of course it didn’t perform gem env as I expected.
Ungummed, as it were, it works fine. E.g.:

irb(main):001:0> a=gem env
=> “RubyGems Environment:\n - RUBYGEMS VERSION: 1.3.1\n - RUBY
VERSION: 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]\n - INSTALLATION
DIRECTORY: /usr/lib/ruby/gems/1.8\n - RUBY EXECUTABLE:
/usr/bin/ruby1.8\n - EXECUTABLE DIRECTORY: /usr/bin\n - RUBYGEMS
PLATFORMS:\n - ruby\n - x86-linux\n - GEM PATHS:\n -
/usr/lib/ruby/gems/1.8\n - /home/tomc/.gem/ruby/1.8\n - GEM
CONFIGURATION:\n - :update_sources=> true\n - :verbose =>
true\n - :benchmark => false\n - :backtrace => false\n -
:bulk_threshold => 1000\n - REMOTE SOURCES:\n -
RubyGems.org | your community gem host”
irb(main):002:0>

I leave it to you to get the code to have StringScanner find and return
the path. Somehow I keep thinking regular expressions might be helpful
here, but I dare not there. I think I hear the ice cracking already.

t.

–

Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< [email protected] >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)
9

Aaron S. wrote:

found it. try this:

$ irb
$ require “rubygems”
$ puts Gem.default_path

-A

Super - easier. I do get 2 paths, though -
/home/tomc/.gem/ruby/1.8
/usr/lib/ruby/gems/1.8

So you’ll still have to locate and extract, but that’s nothing (and
maybe your install is set up differently…?)

Good luck.

t.

–

Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< [email protected] >> (email)
<< TomCloyd.com >> (website)
<< sleightmind.wordpress.com >> (mental health weblog)
10

Tom C. wrote:

Aaron S. wrote:

found it. try this:

$ irb
$ require “rubygems”
$ puts Gem.default_path

-A

Super - easier. I do get 2 paths, though -
/home/tomc/.gem/ruby/1.8
/usr/lib/ruby/gems/1.8

So you’ll still have to locate and extract, but that’s nothing (and
maybe your install is set up differently…?)

Thanks for this thread - exactly what I needed as well. I think code to
find the particular library should try prepending the paths returned
from Gem.default_path in order they are returned, as a gem installed in
a user directory should trump a system gem.

Andy

11

found it. try this:

$ irb
$ require “rubygems”
$ puts Gem.default_path

-A