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Light weight support for JSON

From: Yair Lenga
Subject: Light weight support for JSON
Date: Sun, 28 Aug 2022 09:24:56 -0400


Over the last few years, JSON data becomes a integral part of processing.
In many cases, I find myself having to automate tasks that require
inspection of JSON response, and in few cases, construction of JSON. So
far, I've taken one of two approaches:
* For simple parsing, using 'jq' to extract elements of the JSON
* For more complex tasks, switching to python or Javascript.

Wanted to get feedback about the following "extensions" to bash that will
make it easier to work with simple JSON object. To emphasize, the goal is
NOT to "compete" with Python/Javascript (and other full scale language) -
just to make it easier to build bash scripts that cover the very common use
case of submitting REST requests with curl (checking results, etc), and to
perform simple processing of JSON files.

* Minimal - Lightweight "json parser" that will convert JSON files to bash
associative array (see below)
* Convert bash associative array to JSON

To the extent possible, prefer to borrow from jsonpath syntax.

Parsing JSON into an associative array.

Consider the following, showing all possible JSON values (boolean, number,
string, object and array).
    "b": false,
    "n": 10.2,
    "s: "foobar",
     x: null,
    "o" : { "n": 10.2,  "s: "xyz" },
     "a": [
         { "n": 10.2,  "s: "abc", x: false },
         {  "n": 10.2,  "s": "def" x: true},

This should be converted into the following array:


# Top level
[_length] = 6                            # Number of keys in object/array
[_keys] = b n s x o a            # Direct keys
[b] = false
[n] = 10.2
[s] = foobar
[x] = null

# This is object 'o'
[o._length] = 2
[o._keys] = n s
[o.n] = 10.2
[o.s] = xyz

# Array 'a'
[a._count] =  2                   # Number of elements in array

# Element a[0] (object)
[a.0._length] = 3
[a.0._keys] = n s x
[a.0.n] = 10.2
[a.0.s] = abc
[a.0_x] = false


I hope that example above is sufficient. There are few other items that are
worth exploring - e.g., how to store the type (specifically, separate the
quoted strings vs value so that "5.2" is different than 5.2, and "null" is
different from null.

I will leave the second part to a different post, once I have some
feedback. I have some prototype that i've written in python - POC - that
make it possible to write things like

declare -a foo
curl http://www.api.com/weather/US/10013 | readjson foo

printf "temperature(F) : %.1f Wind(MPH)=%d" ${foo[temp_f]}, ${foo[wind]}


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