r"""Command-line tool to validate and pretty-print JSON

Usage::

    $ echo '{"json":"obj"}' | python -mjson.tool

    {

        "json": "obj"

    }

    $ echo '{ 1.2:3.4}' | python -mjson.tool

    Expecting property name: line 1 column 2 (char 2)

"""

import sys

import json

def main():

    if len(sys.argv) == 1:

        infile = sys.stdin

        outfile = sys.stdout

    elif len(sys.argv) == 2:

        infile = open(sys.argv[1], 'rb')

        outfile = sys.stdout

    elif len(sys.argv) == 3:

        infile = open(sys.argv[1], 'rb')

        outfile = open(sys.argv[2], 'wb')

    else:

        raise SystemExit("{0} [infile [outfile]]".format(sys.argv[0]))

    try:

        obj = json.load(infile)

    except ValueError, e:

        raise SystemExit(e)

    json.dump(obj, outfile, sort_keys=True, indent=4)

    outfile.write('\n')

if __name__ == '__main__':

    main()