How to pretty-print JSON in a shell script?

Query:

Is there a (Unix) shell script to format JSON in human-readable form?

Basically, I want it to transform the following:

{ "foo": "lorem", "bar": "ipsum" }

… into something like this:

{
    "foo": "lorem",
    "bar": "ipsum"
}

How to pretty-print JSON in a shell script?

With Python 2.6+ you can do:

echo '{"foo": "lorem", "bar": "ipsum"}' | python -m json.tool

or, if the JSON is in a file, you can do:

python -m json.tool my_json.json

if the JSON is from an internet source such as an API, you can use

curl http://my_url/ | python -m json.tool

For convenience in all of these cases you can make an alias:

alias prettyjson='python -m json.tool'

For even more convenience with a bit more typing to get it ready:

prettyjson_s() {
    echo "$1" | python -m json.tool
}

prettyjson_f() {
    python -m json.tool "$1"
}

prettyjson_w() {
    curl "$1" | python -m json.tool
}

for all the above cases. You can put this in .bashrc and it will be available every time in shell. Invoke it like prettyjson_s '{"foo": "lorem", "bar": "ipsum"}'.

Note that in Python 3.5+ the JSON object is no longer sorted by default. To sort, add the --sort-keys flag to the end. I.e. ... | python -m json.tool --sort-keys.

How to format JSON in shell script?

You can use: jq

It’s very simple to use and it works great! It can handle very large JSON structures, including streams. You can find their tutorials here.

Usage examples:

$ jq --color-output . file1.json file1.json | less -R

$ command_with_json_output | jq .

$ jq # stdin/"interactive" mode, just enter some JSON

$ jq <<< '{ "foo": "lorem", "bar": "ipsum" }'
{
  "bar": "ipsum",
  "foo": "lorem"
}

Or use jq with identity filter:

$ jq '.foo' <<< '{ "foo": "lorem", "bar": "ipsum" }'
"lorem"

Answer #3:

I use the “space” argument of JSON.stringify to pretty-print JSON in JavaScript.

Examples:

// Indent with 4 spaces
JSON.stringify({"foo":"lorem","bar":"ipsum"}, null, 4);

// Indent with tabs
JSON.stringify({"foo":"lorem","bar":"ipsum"}, null, '\t');

From the Unix command-line with Node.js, specifying JSON on the command line:

$ node -e "console.log(JSON.stringify(JSON.parse(process.argv[1]), null, '\t'));" \
  '{"foo":"lorem","bar":"ipsum"}'

Returns:

{
    "foo": "lorem",
    "bar": "ipsum"
}

From the Unix command-line with Node.js, specifying a filename that contains JSON, and using an indent of four spaces:

$ node -e "console.log(JSON.stringify(JSON.parse(require('fs') \
      .readFileSync(process.argv[1])), null, 4));"  filename.json

Using a pipe:

echo '{"foo": "lorem", "bar": "ipsum"}' | node -e \
"\
 s=process.openStdin();\
 d=[];\
 s.on('data',function(c){\
   d.push(c);\
 });\
 s.on('end',function(){\
   console.log(JSON.stringify(JSON.parse(d.join('')),null,2));\
 });\
"

Python script to format JSON in a shell script:

Thanks to very helpful pointers mentioned in other answers, here’s a slightly enhanced script I’ve come up with:

#!/usr/bin/python

"""
Convert JSON data to human-readable form.

Usage:
  prettyJSON.py inputFile [outputFile]
"""

import sys
import simplejson as json


def main(args):
    try:
        if args[1] == '-':
            inputFile = sys.stdin
        else:
            inputFile = open(args[1])
        input = json.load(inputFile)
        inputFile.close()
    except IndexError:
        usage()
        return False
    if len(args) < 3:
        print json.dumps(input, sort_keys = False, indent = 4)
    else:
        outputFile = open(args[2], "w")
        json.dump(input, outputFile, sort_keys = False, indent = 4)
        outputFile.close()
    return True


def usage():
    print __doc__


if __name__ == "__main__":
    sys.exit(not main(sys.argv))

And finally,

A simple bash script for pretty JSON printing:

json_pretty.sh

#/bin/bash

grep -Eo '"[^"]*" *(: *([0-9]*|"[^"]*")[^{}\["]*|,)?|[^"\]\[\}\{]*|\{|\},?|\[|\],?|[0-9 ]*,?' | awk '{if ($0 ~ /^[}\]]/ ) offset-=4; printf "%*c%s\n", offset, " ", $0; if ($0 ~ /^[{\[]/) offset+=4}'

Example:

cat file.json | json_pretty.sh

Hope you learned something from this post.

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About ᴾᴿᴼᵍʳᵃᵐᵐᵉʳ

Linux and Python enthusiast, in love with open source since 2014, Writer at programming-articles.com, India.

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