rj

a tool that's like jq but uses Ruby expressions

Usage

# get the first element of an array (Enumerable#first)
tool_that_emits_json | rj '.first'

# get the 3rd element (Array#[])
tool_that_emits_json | rj '[2]'

# get specific fields (Hash#slice)
tool_that_emits_json | rj '.first.slice("foo", "bar")'

# or map them yourself, the second expression will be applied to the result
# of the first.  'item' is the special variable that holds the previous
# result
# this also demonstrates the usage of Hash#dig to fetch nested elements
tool_that_emits_json | rj '.first' '{ one: item["foo"], two: item.dig("bar", "name") }'

# same as above, but for all elements (Enumerable#map)
tool_that_emits_json | rj '.map { |item| { one: item["foo"], two: item.dig("bar", "name") } }'

# instead of `[]` and `dig` you can access an object's fields like methods
# too.
# this only works with keys that aren't already methods (e.g. `first`, `dig`,
# `slice`, ...), and only on objects -- arrays need to be accessed like '[0]'.
tool_that_emits_json | rj '.map { |item| { one: item.foo, two: item.bar.name } }'

Requirements

for building:

• CMake
• Ruby 2.5 or later
• whatever else mruby 3.2.0 needs :^)

Building

# configure it
cmake --preset dev

# compile it
cmake --build --preset dev

# test it
ruby ./test/rj_test.rb

# run it
./build/src/rj