Troubleshooting

There may be cases when a particular command ends up using the system ruby although a later version is specified as default using chruby.

If this happens, refer these:

Basics

What chruby does is almost minimal when it comes to switching Rubies. It just changes the PATH variable depending upon the ruby you specify. For example, when you type chruby ruby-2.0.0-p247 on the command-line, the PATH variable (echo $PATH) will be something similar to:

/Users/<user-name>/.gem/ruby/2.0.0/bin:
/Users/<user-name>/.rubies/ruby-2.0.0-p247/lib/ruby/gems/2.0.0/bin:
/Users/<user-name>/.rubies/ruby-2.0.0-p247/bin:
/usr/local/homebrew/bin:
/usr/local/homebrew/sbin:
/usr/bin:
/bin:
/usr/sbin:
/sbin:
/usr/local/bin:
/opt/X11/bin

Note: that I have the rubies installed under ~/.rubies. If you have them installed in a different directory, ensure you have the RUBIES=(/path/to/rubies/*) directive in your .zshrc or .bash_profile and change the paths here accordingly

You can see that chruby has added the correct ruby to the beginning of the PATH and this is important. If your PATH variable has extraneous directories listed out or if you have any shell commands/settings that set extra directory names to your PATH, then some ruby executables might act weird. So, ensure that the PATH has the correct settings.

GEM_HOME / GEM_PATH

Check the output of gem env

This is the output of the command on my machine:

RubyGems Environment:
  - RUBYGEMS VERSION: 2.0.3
  - RUBY VERSION: 2.0.0 (2013-06-27 patchlevel 247) [x86_64-darwin12.4.0]
  - INSTALLATION DIRECTORY: /Users/<user name>/.gem/ruby/2.0.0
  - RUBY EXECUTABLE: /Users/<user name>/.rubies/ruby-2.0.0-p247/bin/ruby
  - EXECUTABLE DIRECTORY: /Users/<user name>/.gem/ruby/2.0.0/bin
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-darwin-12
  - GEM PATHS:
     - /Users/<user name>/.gem/ruby/2.0.0
     - /Users/<user name>/.rubies/ruby-2.0.0-p247/lib/ruby/gems/2.0.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
     - "gem" => "--no-rdoc"
  - REMOTE SOURCES:
     - https://rubygems.org/

The Gem paths and Ruby paths should be correctly set as per the ruby you specify. ( Actually, this is what chruby does — correctly sets the paths. But sometimes, due to incomplete removal of older managers like rvm or rbenv, you might face some issues. )

rbenv

If you've used rbenv, ensure that you cleaned up the installation well. Make sure you don't have extra rbenv instantiations in your .zshrc and/or .bash_profile. If you want to use the rubies installed via rbenv (ruby-build), you can still do it with chruby without removing them. All you need to do is set the RUBIES directive to point to ~/.rbenv/version/* and then, remove the Rbenv initialization options

eval "$(rbenv init -)"
export PATH="$HOME/.rbenv/bin:$PATH"

should be removed.

PATH

If any of the ruby executables are using a different ruby than what you've specified, the most common reason is that, in your current PATH, the wrong executable is found first.

Let me explain.

Consider a PATH setting like the one below. For some reason, /usr/bin is always at the beginning.

/usr/local/homebrew/bin:
/usr/local/homebrew/sbin:
/usr/bin:
/bin:
/Users/<user-name>/.gem/ruby/2.0.0/bin:
/Users/<user-name>/.rubies/ruby-2.0.0-p247/lib/ruby/gems/2.0.0/bin:
/Users/<user-name>/.rubies/ruby-2.0.0-p247/bin:
/usr/sbin:
/sbin:
/usr/local/bin:
/opt/X11/bin

When you run bundle or gem under this setting, the executable at /usr/bin gets evoked even though the correct ruby is set via chruby.

Moreover, once you run bundle, all the environment settings that are specific to that bundler installation are used for compilation and installation of gems. So, the gcc and other compilers that are required to compile native extensions may fail.

In such cases, before running an executable, check the location of the executable by running which <executable name> (For example which bundle or which gem ). And the executables should be under /Users/<user-name>/.gem/ruby/2.0.0/bin/<executable name>. If this is instead set as /usr/bin/, then that executable will use the system ruby (1.8.7) even if a different ruby is set.

Another caveat with PATH lookups is that if the executable is not found in the first directories, then the search happens in the other directories listed. This, combined with a faulty gem env where-in it lists a different ruby that the one required, might result in invoking a wrong executable.