gem installしたgemのパスを知りたい

Ruby

gemのインストール場所は、$ gem environment の出力結果の INSTALLATION DIRECTORY で分かる。

❯ gem environment  
RubyGems Environment:
  - RUBYGEMS VERSION: 3.2.3
  - RUBY VERSION: 3.0.0 (2020-12-25 patchlevel 0) [x86_64-darwin19]
  - INSTALLATION DIRECTORY: /Users/mi/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0
  - USER INSTALLATION DIRECTORY: /Users/mi/.gem/ruby/3.0.0
  - RUBY EXECUTABLE: /Users/mi/.rbenv/versions/3.0.0/bin/ruby
  - GIT EXECUTABLE: /usr/local/bin/git
  - EXECUTABLE DIRECTORY: /Users/mi/.rbenv/versions/3.0.0/bin
  - SPEC CACHE DIRECTORY: /Users/mi/.gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /Users/mi/.rbenv/versions/3.0.0/etc
  - RUBYGEMS PLATFORMS:
     - ruby
     - x86_64-darwin-19
  - GEM PATHS:
     - /Users/mi/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0
     - /Users/mi/.gem/ruby/3.0.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /Users/mi/.rbenv/versions/3.0.0/bin
     - /usr/local/Cellar/rbenv/1.1.2/libexec
     - /Users/mi/.rbenv/plugins/ruby-build/bin
     - /usr/local/Cellar/vim/8.2.1600/bin
     - /Users/mi/.rbenv/shims
     - /Users/mi/.rbenv/bin
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin

$ gem environment gemdir でも分かる

/Users/mi/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0