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

Usage::

 $ echo '{"json":"obj"}' | python -m json.tool
 {
 "json": "obj"
 }
 $ echo '{ 1.2:3.4}' | python -m json.tool
 Expecting property name enclosed in double quotes: line 1 column 3 (char 2)

"""
import argparse
import json
import sys


def main():
 prog = 'python -m json.tool'
 description = ('A simple command line interface for json module '
 'to validate and pretty-print JSON objects.')
 parser = argparse.ArgumentParser(prog=prog, description=description)
 parser.add_argument('infile', nargs='?', type=argparse.FileType(),
 help='a JSON file to be validated or pretty-printed')
 parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'),
 help='write the output of infile to outfile')
 parser.add_argument('--sort-keys', action='store_true', default=False,
 help='sort the output of dictionaries alphabetically by key')
 options = parser.parse_args()

 infile = options.infile or sys.stdin
 outfile = options.outfile or sys.stdout
 sort_keys = options.sort_keys
 with infile:
 try:
 obj = json.load(infile)
 except ValueError as e:
 raise SystemExit(e)
 with outfile:
 json.dump(obj, outfile, sort_keys=sort_keys, indent=4)
 outfile.write('\n')


if __name__ == '__main__':
 main()