How to parse JSON with Bash

Before delving into the process of parsing JSON in a shell script, let's clear up any confusion surrounding the terms "shell" and "Bash."

Shell scripting

A shell script is a series of commands written in the shell programming language. The shell is a command-line interface that allows users to interact with an operating system by typing commands. Shell scripts are used to automate tasks, execute commands, and perform various operations using these commands.

Bash (Bourne Again Shell)

Bash is a specific shell type and is one of the most commonly used shells in Unix-like operating systems. It's an enhanced version of the original Unix shell, the Bourne shell (sh). Bash provides additional features, improved usability, and compatibility with various shell scripts.

Now that we have clarified the distinction between shell scripting and Bash let's proceed with parsing JSON in a Bash shell script. JSON, short for JavaScript Object Notation, is an organized data structure commonly seen in modern APIs. It's like a standardized format for sharing information between different systems. Think of it as a translator that humans and machines can easily understand.

Integrating JSON in shell scripting

Although shell scripting isn't naturally equipped to handle JSON, there's a handy tool called jq that can make it work. It's like adding a new tool to our toolbox. We need to install jq using the following command.

Parsing JSON Data with jq

Here's a simple breakdown of how we can use jq to understand and use JSON data in the shell script:

Step 1: Creating the JSON File

Imagine the JSON file as a well-organized list. We create a file called names.json with a list of people's names and IDs. It's similar to making a shopping list, but for data:

Step 2: Writing the shell script

Think of a shell script as a set of instructions for our computer. We write a script named myscript.sh that tells the computer how to read and understand the JSON data:

Step 3: Running the script

Before running the script, we need to give the computer permission to run it. We do this by running the following command:

Now, let's execute the script:

Output

Following is the expected output of the script.

Code implementation

Following is the implementation of the steps describes above:

Code explanation

Following is the line-by-line breakdown of the code given above:

• Line 1: Specify the interpreter for the script, indicating that it's a shell script using the /bin/sh interpreter.

• Line 2: Read the contents of the file names.json and stores them in a variable named json.

• Line 3: Extracts the value associated with the key "number" from the JSON data stored in the json variable. The jq command is used to parse the JSON data. The -r option outputs the raw value without quotes, storing the result in the number variable.

• Line 4: Extract the "name" key values from each object within the "people" array in the JSON data. The jq command is again used, and the result is stored in the names variable. The tr command is then applied to replace newline characters (\n) with spaces, effectively joining the names together in a single line.

• Line 5: Print the message "Number of people:" followed by the value stored in the number variable.

• Line 6: Prints the message "Names:" followed by the value stored in the names variable.