How to handle JSON on the command line
Tags: json, commandline, api, jq
Published: 2021-04-19 21:02:06


Some tool for working with json on the command line would be handy when debugging REST APIs. You can make a request, receive a response and immediately parse it, highlighting the necessary objects and fields.

  

Consider a command line json utility called [jq](https://stedolan.github.io/jq/) that does exactly what we want. With its help, you can parse, filter, compare and transform json data effortlessly.

  

To install on Linux, you can simply download the binaries (there are 32 and 64 bit versions):

  

```bash

$ wget http://stedolan.github.io/jq/download/linux32/jq (32-bit)

$ wget http://stedolan.github.io/jq/download/linux64/jq (64-bit)

$ chmod +x ./jq

$ sudo cp jq /usr/bin

```

  

There are also [builds](https://stedolan.github.io/jq/download/) for Windows and Mac OS X. The complete source code is [licensed under the MIT license](https://opensource.org/licenses/MIT) .

  

Let's look at some examples. Let's say we have the following json schema.

  

```bash

  

$ cat books.json

  

{

"type": "examples",

"intro": {

"catgoery": "tech"

},

"books": [

{

"isbn": "9781593275846",

"title": "Eloquent JavaScript, Second Edition",

"subtitle": "A Modern Introduction to Programming",

"author": "Marijn Haverbeke",

"published": "2014-12-14T00:00:00.000Z",

"publisher": "No Starch Press",

"pages": 472,

"description": "JavaScript lies at the heart of almost every modern web application, from social apps to the newest browser-based games. Though simple for beginners to pick up and play with, JavaScript is a flexible, complex language that you can use to build full-scale applications.",

"website": "http://eloquentjavascript.net/"

},

{

"isbn": "9781449331818",

"title": "Learning JavaScript Design Patterns",

"subtitle": "A JavaScript and jQuery Developer's Guide",

"author": "Addy Osmani",

"published": "2012-07-01T00:00:00.000Z",

"publisher": "O'Reilly Media",

"pages": 254,

"description": "With Learning JavaScript Design Patterns, you'll learn how to write beautiful, structured, and maintainable JavaScript by applying classical and modern design patterns to the language. If you want to keep your code efficient, more manageable, and up-to-date with the latest best practices, this book is for you.",

"website": "http://www.addyosmani.com/resources/essentialjsdesignpatterns/book/"

},

{

"isbn": "9781449365035",

"title": "Speaking JavaScript",

"subtitle": "An In-Depth Guide for Programmers",

"author": "Axel Rauschmayer",

"published": "2014-02-01T00:00:00.000Z",

"publisher": "O'Reilly Media",

"pages": 460,

"description": "Like it or not, JavaScript is everywhere these days-from browser to server to mobile-and now you, too, need to learn the language or dive deeper than you have. This concise book guides you into and through JavaScript, written by a veteran programmer who once found himself in the same position.",

"website": "http://speakingjs.com/"

},

{

"isbn": "9781491950296",

"title": "Programming JavaScript Applications",

"subtitle": "Robust Web Architecture with Node, HTML5, and Modern JS Libraries",

"author": "Eric Elliott",

"published": "2014-07-01T00:00:00.000Z",

"publisher": "O'Reilly Media",

"pages": 254,

"description": "Take advantage of JavaScript's power to build robust web-scale or enterprise applications that are easy to extend and maintain. By applying the design patterns outlined in this practical book, experienced JavaScript developers will learn how to write flexible and resilient code that's easier-yes, easier-to work with as your code base grows.",

"website": "http://chimera.labs.oreilly.com/books/1234000000262/index.html"

}

]

}

  

```

  

We get a simple field:

  

```bash

$ cat books.json | jq '.type'

"examples"

```

  

Now it's a little more complicated, with nesting:

  

```bash

$ cat books.json | jq '.intro.catgoery'

"tech"

```

  

For arrays:

  

```bash

$ cat json.txt | jq '.books[1].title'

"Learning JavaScript Design Patterns"

```

  

Fetching a specific list of fields:

  

```bash

$ cat json.txt | jq '.books[1] | {author, pages}'

{

"author": "Addy Osmani",

"pages": 254

}

```

  

you can check the [documentation](https://stedolan.github.io/jq/manual) for more information