jr: command-line JSON processor for Rubyists

jr is jq like JSON processor.
Its script can be written not a specific language but Ruby!

jr in action

Installation

Add this line to your application's Gemfile:

gem 'jr-cli'

And then execute:

$ bundle

Or install it yourself as:

$ gem install jr-cli

Usage

jr filter can be written in Ruby!

$ jr [options] <jr filter> [file...]

You can also read JSON not from files but from STDIN.

options

        --require FILE               require the FILE before execution
    -c, --compact-output             output each JSON in single line
    -f, --from-file FILE             read filter from file
    -r, --raw-output                 output strings as raw output
    -R, --raw-input                  read each line as string
    -C, --color-output               output with colors even if writing to a pipe or a file
    -M, --monochrome-output          output without colors
    -n, --null-input                 use null as input instead of any files

jr filter tutorial

Let's process JSON of GitHub API!

At first, download JSON of repos into your local to avoid API rate limit.

$ curl -s 'https://api.github.com/users/yuya-takeyama/repos?per_page=100' > repos.json

Unwrap Array with Enumerable#unwrap

Because response from GET /users/:username/repos is wrapped with Array, unwrap it using Enumerable#unwrap.
It's a built-in method of jr.
You'll get stream of JSON reperesents repositories.

$ jr 'unwrap' repos.json

Aggregate data with methods of Enumerable

Enumerable has many useful methods and you can transform data with them.

$ jr 'unwrap.group_by(&:language).map{|k, v| [k, v.size] }.sort_by{|k, v| -v }' repos.json
[
  "Ruby",
  28
]
[
  "PHP",
  22
]
[
  "Go",
  17
]
(...omitted...)
[
  "VimL",
  1
]
[
  "CoffeeScript",
  1
]
[
  "Perl",
  1
]

Output as text

You can transform JSONs into String and output as raw text using -r option.

$ jr 'unwrap.group_by(&:language).map{|k, v| [k, v.size] }.sort_by{|k, v| -v }.map{|l, s| "#{s}\t#{l}" }' -r repos.json
28      Ruby
22      PHP
17      Go
12      JavaScript
11
3       CSS
2       Shell
2       C
1       VimL
1       CoffeeScript
1       Perl

Basic mechanism

It's helpful to know jr's basic mechanism.
Shortly, jr is implemented like below.

json_enumerator.instance_eval { your_jr_filter_runs_here }
# And print its result

Contributing

  1. Fork it ( https://github.com/yuya-takeyama/jr/fork )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request