Ruby programmatically installing a gem - ruby

Question

If I install a gem programmatically using Backticks in script with gem install gem_name as:
if not_gem_installed
`gem install my_gem`
end
require 'my_gem'
and then require the gem, a LoadError comes up. Any way to fix this?

Answer 1

I've tried installation of gems with backticks and found that I have the same issues as mentioned in question. I see that it's not the optimal choice for this job.
I would suggest to use Gem for search of gems and installation.
require 'rubygems/commands/install_command'
def find_or_install(gem_name)
Gem::Specification::find_by_name(gem_name)
rescue Gem::LoadError
install_gem(gem_name)
end
def install_gem(gem_name)
cmd = Gem::Commands::InstallCommand.new
cmd.handle_options [gem_name]
cmd.execute
rescue Gem::SystemExitException => e
puts "FAILURE: #{e.exit_code}"
end
https://gist.github.com/adamjmurray/3154437 - Gist with good examples

Answer 2

Since you are not using RubyGems, you need to require specific file from your gem's path. RubyGems overrides the require method so that it looks for paths file to include from gem paths in your Gemfile. So, make sure you specify correct path to your gem's main .rb file.
if not_gem_installed
`gem install my_gem`
end
require 'path/to/my_gem'
You can check the paths ruby will look into by printing the value of $: in your file/irb or by running gem environment command in your command line.
uzbekjon#mini:~$ gem environment
RubyGems Environment:
- RUBYGEMS VERSION: 2.5.1
- RUBY VERSION: 2.3.0 (2015-12-25 patchlevel 0) [x86_64-darwin15]
- INSTALLATION DIRECTORY: /Users/uzbekjon/.rvm/gems/ruby-2.3.0
- USER INSTALLATION DIRECTORY: /Users/uzbekjon/.gem/ruby/2.3.0
- RUBY EXECUTABLE: /Users/uzbekjon/.rvm/rubies/ruby-2.3.0/bin/ruby
- EXECUTABLE DIRECTORY: /Users/uzbekjon/.rvm/gems/ruby-2.3.0/bin
- SPEC CACHE DIRECTORY: /Users/uzbekjon/.gem/specs
- SYSTEM CONFIGURATION DIRECTORY: /Users/uzbekjon/.rvm/rubies/ruby-2.3.0/etc
- GEM PATHS:
- /Users/uzbekjon/.rvm/gems/ruby-2.3.0
- /Users/uzbekjon/.rvm/gems/ruby-2.3.0#global
- GEM CONFIGURATION:
...
=== OR with $: ===
uzbekjon#mini:~$ irb
2.3.0 :001 > $:
=> ["/Users/uzbekjon/.rvm/gems/ruby-2.3.0#global/gems/did_you_mean-1.0.0/lib", "/Users/uzbekjon/.rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0", "..."]
Alternatively
You can require simply use bundler in your script.
if not_gem_installed
`gem install my_gem`
end
require 'rubygems' # <= This line here
require 'path/to/my_gem'