tool.py revision 940e2074123f7d18236e2e8ee08044b400261c42 
1r"""Command-line tool to validate and pretty-print JSON
2
3Usage::
4
5    $ echo '{"json":"obj"}' | python -m json.tool
6    {
7        "json": "obj"
8    }
9    $ echo '{ 1.2:3.4}' | python -m json.tool
10    Expecting property name enclosed in double quotes: line 1 column 3 (char 2)
11
12"""
13import argparse
14import json
15import sys
16
17
18def main():
19    prog = 'python -m json.tool'
20    description = ('A simple command line interface for json module '
21                   'to validate and pretty-print JSON objects.')
22    parser = argparse.ArgumentParser(prog=prog, description=description)
23    parser.add_argument('infile', nargs='?', type=argparse.FileType(),
24                        help='a JSON file to be validated or pretty-printed')
25    parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'),
26                        help='write the output of infile to outfile')
27    options = parser.parse_args()
28
29    infile = options.infile or sys.stdin
30    outfile = options.outfile or sys.stdout
31    with infile:
32        try:
33            obj = json.load(infile)
34        except ValueError as e:
35            raise SystemExit(e)
36    with outfile:
37        json.dump(obj, outfile, sort_keys=True, indent=4)
38        outfile.write('\n')
39
40
41if __name__ == '__main__':
42    main()
43