Скачать или смотреть Implementing a Simple Template Renderer in Bash Using JSON Models and JQ

Learn how to create a simple template renderer in Bash using JSON data and the `jq` utility. This guide covers practical steps to easily replace placeholders in your templates with dynamic JSON values.
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How to Implement a Simple Template Renderer in Bash Using JSON Models

In the world of scripting and automation, there are often scenarios where you need to populate templates with data dynamically. One common use case is rendering templates with data stored in JSON format. Have you ever found yourself wrestling with complicated template engines or messy approaches? If so, you're not alone.

In this guide, we will explore how to create a simple template renderer using jq and other utilities in Bash. We’ll break it down into manageable sections, ensuring you can follow along easily.

Understanding the Problem

Imagine you have the following JSON data:

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Now, let's say you want to display this data in a human-readable format using a template:

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The goal is to replace the placeholders in the template (e.g., {.a}, {.b}, and {.c[].x}) with the corresponding values from the JSON data. The rendered output we expect should look like this:

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The Solution Using JQ

JQ is a powerful command-line tool for processing JSON data. Here’s a simple JQ-only solution to the stated problem.

Steps to Render Your Template

Set Your JSON Data: First, assign your JSON data to a variable in your Bash script.

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Create Your Template File: Write your template into a text file (let's call it template.txt):

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Render the Template: Use the following jq command to process the template and substitute values from the JSON:

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Explanation of the JQ Command

-n: This flag signifies that jq should not read any input data from the standard input, but instead use the arguments provided.

-r: This option tells jq to produce raw output rather than JSON-quoted output.

--argjson json "$json": This part allows us to pass our JSON variable to jq as a variable.

inputs: This function processes inputs (lines from our template file).

gsub: This is used for global substitution; it searches for patterns in the input and replaces them with the specified values.

Conclusion

With this basic setup, you can now create dynamic templates that seamlessly integrate JSON data into your Bash scripts. The approach outlined here provides a foundation that you can expand upon, allowing for more complex templates and greater flexibility.

In future posts, we'll explore ways to enhance this renderer and tackle more complex JSON structures. Until then, happy scripting!