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JSON is a textual method for representing JavaScript object literals and arrays and scalar data. It is relatively easier to read and write, and easier for manageable software to parse and generate.

JSON is commonly used to serialize structured data and exchange it over a network, usually between a server and a web application.

Pretty Printing JSON in Shell Script

When working with JSON, one might want to format its output in a more human-readable format. Consider the following JSON object:

{"name": "Ali", "rollno": 123, "fathername": "Muhammad", "mothername": "Qimra", "semester": 5, "roomno": "b-12", }

Understanding the properties of the above JSON object is difficult enough with a dozen properties, so imagine what a nightmare it would be if there were hundreds of properties.

Therefore, it is important to format it into a more human-friendly format, such as the following JSON property:

{"name": "Ali",
"rollno": 123,
"fathername": "Muhammad",
"mothername": "Qimra",
"semester": 5,
"roomno": "b-12"}

Notice how much cleaner it looks now. We will now go through a number of ways to achieve this.

With python 2.6+ you can use:

echo '{"key1": "val1", "keyn": "valn"}' | python -m json.tool
# or use
echo '{"key1": "val1", "keyn": "valn"}' | python2 -m json.tool
# or use
echo '{"key1": "val1", "keyn": "valn"}' | python3 -m json.tool

The output will look like this:

{
    "key1": "val1",
    "keyn": "valn"
}

However, if you do not have Python, Python2, or Python3 installed, you will receive one of the following errors:

Command 'python' not found
Command 'python2' not found
Command 'python3' not found

To avoid this error, use the following command:

sudo apt install python python2 python3

Another way is, if you store the JSON object in a JSON file, run the following command:

python -m json.tool <path to json file>.json

If, just in case, the JSON comes from an internet source like an API, then use:

curl <url> | python -m json.tool

We will now see other ways to achieve the above goals.

Suppose we have a file my_json.json with the following structure:

{ "key1": "val1", " keyn": "valn" }

Note that we use .to specify the current directory, since the file resides in that directory:

sudo jq . my_json.json | less –R

jq '.key1' <<< '{ "key1": "val1", " keyn": "valn" }'

cat my_json.json| jq .

echo '{ "key1": "val1", " keyn": "valn" }' | npx json

To use jq, you must install it using the following command:

sudo apt install jq

The output of the first, third (using a pipe to transfer data from the file my_json.json to the process jq), and fourth methods are as follows:

{
    "key1": "val1",
    "keyn": "valn"
}

The fourth method requires npxa dependency, but don't worry when running that command. If you don't have npx installed, it will be installed automatically.

The second method defines a JSON object and prints the value of key1. Here is its output:

"val1"

We can also combine Python's json.tool with pigmentize to pretty-print JSON objects. Consider the following command:

echo '{ "key1": "val1", " keyn": "valn" }' | python -m json.tool | pygmentize –g

The output of the above command is as follows:

{
    "key1": "val1",
    "keyn": "valn"
}

However, to use the command above, you must install pigmentize. To install pigmentize, use the following command:

sudo apt install python3-pygments