What is the default search path for Ruby gems? i.e. the default GEM_HOME

Question

What is the default search path for Ruby gems? I'm trying to figure what directories I can pass to gem's --install-dir switch, so that I don't have to set the environment variable GEM_HOME for the gems to be found.

In particular, if I install the gem jekyll via

$ gem install --bindir /usr/local/bin --install-dir /usr/local/lib/ruby/gems/1.8 jekyll

then /usr/local/bin/jekyll can't find its libraries without explicitly setting GEM_HOME:

$ jekyll --help
/usr/lib/ruby/1.8/rubygems.rb:779:in `report_activate_error': Could not find RubyGem jekyll (>= 0) (Gem::LoadError)
    from /usr/lib/ruby/1.8/rubygems.rb:214:in `activate'
    from /usr/lib/ruby/1.8/rubygems.rb:1082:in `gem'
    from /usr/local/bin/jekyll:18
$ GEM_HOME=/usr/local/lib/ruby/gems/1.8 jekyll --help
Jekyll is a blog-aware, static site generator.
[ ... ]

It seems that ruby itself will look in the directories listed in the Ruby variable $LOAD_PATH, which can be augmented by the environment variable RUBYLIB. However, where does the rubygem system search for gems?

Solution

Type gem env. That will tell you what you want to know.

Comments

[barlop]

it gives three directories eg on osx /Library/Ruby/Gems/2.3.0 . and /Users/apple/.gem/ruby/2.3.0 and /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/l‌​ib/ruby/gems/2.3.0 . So which is default for GEM_PATH and which is default for GEM_HOME?

[David Hull]

You can use gem env gemhome and gem env gempath. To find the user gemhome, you can use ruby -e 'print Gem.user_dir'