jrq

jrq is a CLI JSON processor for Rubyists. jrq enable you to filter/map/reduce JSON without studying new syntax.

$ echo '{"foo": [1, 2, 3], "bar": 100 }' \
  | jrq '_.foo.reduce(&:+) * _.bar' # => 600

Installation

Add this line to your application's Gemfile:

gem 'jrq'

And then execute:

$ bundle

Or install it yourself as:

$ gem install jrq

Usage

JSON data from STDIN will be parsed and passed as _ variable. Because jrq just evaling given string in the context of Ruby, actually it's almost same as doing like cat a.json | ruby -rjson -e "JSON.load(STDIN)['foo']". Here are some samples below:

_ is a Hash, so _.keys would be nice place to start with.

$ aws ec2 describe-instances \
  | jrq '_.keys'
[
  "Reservations"
]

jrq parses given JSON with Hashie::Mash, so you can access json fields with dot(.) like Ruby's method access.

$ aws ec2 describe-instances \
  | jrq '_.Reservations.class'
Array

Then digging deeper...

$ aws ec2 describe-instances \
  | jrq -r '_.Reservations.map{|r| r.keys }.flatten.uniq'
[
  "OwnerId",
  "ReservationId",
  "Groups",
  "Instances",
  "RequesterId"
]

... to get information you need.

$ aws ec2 describe-instances \
  | jrq 'ins = _.Reservations.first.Instances.first;
        [ins.InstanceId, ins.VpcId, ins.SubnetId, ins.PrivateIpAddress]'
[
  "i-aaaaaaaa",
  "vpc-5dxxxxx8",
  "subnet-a1xxxxx6",
  "172.31.25.92"
]

$ aws ec2 describe-instances \
  | jrq '_.Reservations.map{|r| r.Instances.map{|i| i.InstanceId } }.flatten'
[
  "i-aaaaaaaa",
  "i-bbbbbbbb",
  "i-cccccccc",
  "i-dddddddd",
]

With -r or --raw option, raw output would be displayed. It's suitable for passing to another program as input.

$ aws ec2 describe-instances \
  | jrq -r '_.Reservations.map{|r| r.Instances.map{|i| i.InstanceId } }.flatten'
i-aaaaaaaa
i-bbbbbbbb
i-cccccccc
i-dddddddd

You can even require another Ruby library.

$ curl -s https://ip-ranges.amazonaws.com/ip-ranges.json \
  | jrq 'require "ipaddr"; _.prefixes.select{|p| p.region == "ap-northeast-1" }.map{|p| IPAddr.new(p.ip_prefix).to_i.to_s(2) }'

[
  "11011000000000000000000000000",
  "101110001100111110000000000000",
  "110100010001000000000000000000",
  "110100010111000011110000000000",
  "110100010111000101000000000000",
  ...

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment. Run bundle exec jrq to use the gem in this directory, ignoring other installed copies of this gem.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Build & Push to rubygems.org

$ gem build jrq.gemspec

then

$ gem install jrq-x.y.z.gem

$ gem push jrq-x.y.z.gem

Plan & TODOs

color
launch REPL when STDIN isn't given
- jrq foo.json => also launch REPL
prepare sample JSON data
- AWS ip-ranges.json
- CloudFormation Template
- ECS Task Definition
- JSON Schema / Swagger

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/memerelics/jrq/issues

License

The gem is available as open source under the terms of the MIT License.

thash/jrq