如何找出用 Ruby 打包的库的版本，例如 json？

Question

Some Ruby functionality packaged with the Ruby distribution (and not needing to be installed as gems explicitly or via bundler). JSON is one example ( require 'json' ). It can be required in Ruby code but doesn't require gem installation.

Yet JSON is a gem on Github, at https://github.com/flori/json .

So how can I know which version of that gem I'm getting when I require 'json' in my code?

Answer 1

Alternatively many ruby gems specify their version in a constant.

You can utilize this to determine the version you are using in code or in console as well eg

require 'json'
JSON.constants.grep(/VERSION/)
#=>[:VERSION, :VERSION_ARRAY, :VERSION_MAJOR, :VERSION_MINOR, :VERSION_BUILD]
JSON::VERSION
#=> 2.5.1
require 'bundler'
Bundler.constants.grep(/VERSION/)
#=> [:VERSION]
Bundler::VERSION
#=> 2.2.3

Answer 2

You can find the Ruby home directory, and search below it for a directory of the appropriate name, and then inspect its version.rb file. For example, with rvm-managed rubies, I can do this (on a Posix-complaint system such as Linux or Mac OS):

$ cd $(which ruby)/../..; pwd
/Users/keith.bennett/.rvm/rubies/ruby-3.0.1

$find . -type d -name '*json*'
./lib/ruby/3.0.0/psych/json
./lib/ruby/3.0.0/json
./lib/ruby/3.0.0/rdoc/generator/template/json_index
./lib/ruby/3.0.0/x86_64-darwin19/json
./lib/ruby/gems/3.0.0/gems/json-2.5.1
./lib/ruby/gems/3.0.0/gems/rbs-1.0.4/stdlib/json

I can cat ./lib/ruby/3.0.0/json/version.rb | grep 'VERSION ' cat ./lib/ruby/3.0.0/json/version.rb | grep 'VERSION ' (include the space after "VERSION"), and I get:

  VERSION         = '2.5.1'

..which is also the version of the gem in the gems directory included in the listing above.

So I can see that 2.5.1 is my JSON version.