northscaler/ymlx repository overview

Command-line YAML processing tool

⁠Features

• Plain JavaScript to manipulate document(s)

⁠Install

$ npm install -g ymlx

⁠Usage

Pipe into ymlx any YAML and anonymous function for reducing it.

$ cat my.yaml | ymlx [code ...]

⁠Anonymous function

Use an anonymous function as reducer which gets YAML as an object and processes it:

$ echo 'foo: [bar: value]' | ymlx 'x => x.foo[0].bar'
value

⁠this Binding

If you don't pass anonymous function param => ..., code will be automatically transformed into anonymous function. And you can get access to YAML by this keyword:

$ echo 'foo: [bar: value]' | ymlx 'this.foo[0].bar'
value

⁠Multiple Documents

You can pass a YAML file with multiple documents (using the --- separator), and your commands will be applied to each document.

# test.yml
---
foo:
- bar: value
---
foo:
- bar: another

$ cat test.yml | ymlx 'this.foo[0].bar'
---
value
---
another

⁠Chain

You can pass any number of anonymous functions for reducing JSON:

$ echo 'foo: [bar: value]' | ymlx 'x => x.foo' 'this[0]' 'this.bar'
value

⁠Generator

If passed code contains yield keyword, generator expression⁠ will be used:

$ curl ... | ymlx 'for (let user of this) if (user.login.startsWith("a")) yield user'

Access to YAML through this keyword:

# test.yml
- a
- b

$ cat test.yml | ymlx 'yield* this'
- a
- b

$ cat test.yml | ymlx 'yield* this; yield "c";'
- a
- b
- c

⁠Update

You can update existing YAML using spread operator:

$ echo 'count: 0' | ymlx '{...this, count: 1}'
count: 1

⁠Use npm package

Use any npm package by installing globally or in the current working directory:

$ npm install lodash # -g if you want
$ cat 'count: 0' | ymlx 'require("lodash").keys(this)'
- count

⁠Formatting

$ echo '[1,2,3]' | ymlx 'this.reduce((a,n) => a += n.toString(), "concat: ")'
'concat: 123'

⁠Inspiration

ymlx was inspired by fx⁠

⁠Related

• jq⁠ – cli JSON processor on C
• jsawk⁠ – like awk, but for JSON
• json⁠ – another JSON manipulating cli library
• jl⁠ – functional sed for JSON on Haskell

⁠License

MIT