How can I pretty-print JSON in a shell script?

Question

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"
}

Answer 1

$ echo '{ "foo": "lorem", "bar": "ipsum" }' \
> | python -c'import fileinput, json;
> print(json.dumps(json.loads("".join(fileinput.input())),
>                  sort_keys=True, indent=4))'
{
    "bar": "ipsum",
    "foo": "lorem"
}

NOTE: It is not the way to do it.

The same in Perl:

$ cat json.txt \
> | perl -0007 -MJSON -nE'say to_json(from_json($_, {allow_nonref=>1}), 
>                                     {pretty=>1})'
{
   "bar" : "ipsum",
   "foo" : "lorem"
}

Note 2: If you run

echo '{ "Düsseldorf": "lorem", "bar": "ipsum" }' \
| python -c'import fileinput, json;
print(json.dumps(json.loads("".join(fileinput.input())),
                 sort_keys=True, indent=4))'

the nicely readable word becomes \u encoded

{
    "D\u00fcsseldorf": "lorem", 
    "bar": "ipsum"
}

If the remainder of your pipeline will gracefully handle unicode and you'd like your JSON to also be human-friendly, simply use ensure_ascii=False

echo '{ "Düsseldorf": "lorem", "bar": "ipsum" }' \
| python -c'import fileinput, json;
print json.dumps(json.loads("".join(fileinput.input())),
                 sort_keys=True, indent=4, ensure_ascii=False)'

and you'll get:

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

Answer 2

jj is super-fast, can handle ginormous JSON documents economically, does not mess with valid JSON numbers, and is easy to use, e.g.

jj -p # for reading from STDIN

or

jj -p -i input.json

It is (2018) still quite new so maybe it won’t handle invalid JSON the way you expect, but it is easy to install on major platforms.

Answer 3

Thanks to J.F. Sebastian's very helpful pointers, 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))

Answer 4

Or, with Ruby:

echo '{ "foo": "lorem", "bar": "ipsum" }' | ruby -r json -e 'jj JSON.parse gets'

Answer 5

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 nodejs, 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));\
 });\
"

Answer 6

On *nix, reading from stdin and writing to stdout works better:

#!/usr/bin/env python
"""
Convert JSON data to human-readable form.

(Reads from stdin and writes to stdout)
"""

import sys
try:
    import simplejson as json
except:
    import json

print json.dumps(json.loads(sys.stdin.read()), indent=4)
sys.exit(0)

Put this in a file (I named mine "prettyJSON" after AnC's answer) in your PATH and chmod +x it, and you're good to go.