til/ruby/install-and-require-gems-inline-without-gemfile.md

Install And Require Gems Inline Without Gemfile

Bundler has an inline feature where you can declare gems that should be installed and required for the current file without the use of a Gemfile. This is useful for creating a single-file Ruby script that can define its own dependencies.

Require "bundler/inline" and then add a gemfile block toward the top of the script to specify the source and any gems.

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "httparty"
end

When the script gets run (e.g. ruby script.rb), it will install the gems (if they haven't already been installed) and then run the script. You can specify version constraints just like you'd do in a Gemfile.

Here is a single-file script using this approach that I wrote to interact with the Kit API.

#!/usr/bin/env ruby
require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "httparty"
end

require "json"
require_relative "kit_client"

API_SECRET = ENV["KIT_API_SECRET"]

def fetch_all_tags(api_secret)
  client = KitClient.new("https://api.kit.com/v4", api_secret)

  tags = []
  after_cursor = nil

  loop do
    params = {per_page: 1000}
    params[:after] = after_cursor if after_cursor

    response = client.get("/tags", params)

    data = JSON.parse(response.body)
    tags.concat(data["tags"])

    break unless data["pagination"]["has_next_page"]
    after_cursor = data["pagination"]["end_cursor"]
  end

  tags
end

tags = fetch_all_tags(API_SECRET)

tags.each do |tag|
  puts tag
end

Because I've specified the shebang at the top of the file (and assuming I've chmod +x fetch_tags.rb), I can run this directly as a script with ./fetch_tags.rb.

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