I recently upgraded to Ubuntu 9.04 and I have issues using gems. I installed Ruby, Rubygems and Rails using apt-get. The rails
command does work.
I then installed capistrano and other gems, such as heroku. In order to do that, I used the command:
sudo gem install XXX
When I want to use the cap
command it does not work:
bash: cap: command not found
It is the same with the other gem commands.
Do I have something particular to do so that the gem commands work?
The gem command allows you to interact with RubyGems. Ruby 1.9 and newer ships with RubyGems built-in but you may need to upgrade for bug fixes or new features. To upgrade RubyGems, visit the download page. If you want to see how to require files from a gem, skip ahead to What is a gem. Finding Gems.
With the --local ( -l ) option, you would perform a local search through your installed gems. To install a gem, use gem install [gem] . Browsing installed gems is done with gem list . For more information about the gem command, see below or head to RubyGems' docs.
The basic difference is a gem is something that needs to be installed on the system running your Rails application, whereas a plugin is deployed along with your application. More specifically, plugins live in vendor/plugins whereas gems need to be install using rake gem install gem_name.
In the console be located in the gems cache (cd [Ruby Installation version]/lib/ruby/gems/[Ruby version]/cache ) and fire the gem install anygemwithdependencieshere (by example cucumber-2.99. 0 )
You can find where your gems are stored using the gem environment
command. For example:
chris@chris-laptop:~$ gem environment RubyGems Environment: - RUBYGEMS VERSION: 1.3.2 - RUBY VERSION: 1.8.7 (2008-08-11 patchlevel 72) [i486-linux] - INSTALLATION DIRECTORY: /usr/lib/ruby/gems/1.8 - RUBY EXECUTABLE: /usr/bin/ruby1.8 - EXECUTABLE DIRECTORY: /usr/bin - RUBYGEMS PLATFORMS: - ruby - x86-linux - GEM PATHS: - /usr/lib/ruby/gems/1.8 - /home/chris/.gem/ruby/1.8 - GEM CONFIGURATION: - :update_sources => true - :verbose => true - :benchmark => false - :backtrace => false - :bulk_threshold => 1000 - REMOTE SOURCES:
If you look at the "GEM PATHS:" section you can see that gems can be stored in two places on my laptop: /usr/lib/ruby/gems/1.8
or in the .gem
directory in my home dir.
You can also see that executables are stored in EXECUTABLE DIRECTORY which in this case is /usr/bin
.
Because /usr/bin
is in my path this lets me run cap
, merb
, rails
etc.
If for some reason your EXECUTABLE DIRECTORY isn't on your path (for example if it is /var/lib/gems/1.8/bin) then you need to update your PATH variable.
Assuming that you are using the bash shell. You can do this quickly for the current session by typing the following at the shell prompt; let's pretend that you want to add /var/lib/gems/1.8/bin
to the path:
export PATH=$PATH:/var/lib/gems/1.8/bin
and press return. That appends the new directory to the end of the current path. Note the colon between $PATH
and /var/lib/gems/1.8/bin
To set the value for all sessions you will need to edit either your .profile
or .bashrc
file and add the same line to the end of the file. I usually edit my .bashrc
file for no reason other than that's what I've always done. When finished, save the file and then refresh your environment by typing:
bash
at the shell prompt. That will cause the .bashrc
to get reread.
At any point you can check the current value of $PATH
by typing
echo $PATH
at the shell prompt.
Here's a sample from one of my own servers, where my username is "chris" and the machine name is "chris-laptop":
chris@chris-laptop:~$ chris@chris-laptop:~$ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games chris@chris-laptop:~$ chris@chris-laptop:~$ export PATH=$PATH:/var/lib/gems/1.8/bin chris@chris-laptop:~$ chris@chris-laptop:~$ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/var/lib/gems/1.8/bin chris@chris-laptop:~$
"Ruby gems won't load even though installed" highlights a common problem using multiple different versions of Ruby; Sometimes the Gem environment and Gem path get out of sync:
rb(main):003:0> Gem.path => ["/opt/ruby1.9/lib/ruby1.9/gems/1.9.1"] irb(main):004:0> exit
Any Ruby process here is looking only in one place for its Gems.
:~/$ gem env RubyGems Environment: - RUBYGEMS VERSION: 1.3.7 - RUBY VERSION: 1.9.1 (2009-05-12 patchlevel 129) [x86_64-linux] - INSTALLATION DIRECTORY: /opt/ruby1.9/lib/ruby/gems/1.9.1 - RUBY EXECUTABLE: /opt/ruby1.9/bin/ruby1.9 - EXECUTABLE DIRECTORY: /opt/ruby1.9/bin - RUBYGEMS PLATFORMS: - ruby - x86_64-linux - GEM PATHS: - /opt/ruby1.9/lib/ruby/gems/1.9.1 - /home/mark/.gem/ruby/1.9.1 - GEM CONFIGURATION: - :update_sources => true - :verbose => true - :benchmark => false - :backtrace => false - :bulk_threshold => 1000 - REMOTE SOURCES: - http://rubygems.org/
Look carefully at the output of gem environment:
- GEM PATHS: - /opt/ruby1.9/lib/ruby/gems/1.9.1
This isn't the same path as returned by Gem.path:
["/opt/ruby1.9/lib/ruby1.9/gems/1.9.1"]
It's hard to say what exactly caused lib/ruby
to change to lib/ruby1.9
but most likely the developer was working with multiple Ruby versions. A quick mv
or ln
will solve the problem.
If you do need to work with multiple Ruby versions then you really should be using rvm.
As noted by @Chris you need to add the gems environment to your path. You can do this by:
echo 'export PATH=$PATH:/var/lib/gems/1.8/bin' | tee --append ~/.bashrc
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