jcat

#!/usr/bin/python
import json
import sys
from argparse import ArgumentParser

def combine(left, right):
    if isinstance(left, list) and isinstance(right, list):
        return left + right
    elif isinstance(left, dict) and isinstance(right, dict):
        left.update(right)
        return left
    else:
        raise TypeError("Heterogenous JSON types, was (%s, %s)" % (type(left), type(right)))

if __name__ == '__main__':
    parser = ArgumentParser()
    parser.add_argument('files', nargs='+', help='Files containing JSON objects')
    parser.add_argument('--wrap', action='store_true', help='Wrap JSON input in array')
    parser.add_argument('--pretty', action='store_true', help='Pretty-prints JSON output')
    arguments = parser.parse_args()

    files = []
    for filename in arguments.files:
        with open(filename, 'r') as f:
            try:
                content = json.load(f)
                files.append(content)
            except Exception, e:
                print "File '%s': %s" % (filename, e)
                sys.exit()

    if arguments.wrap:
        result = files
    else:
        result = reduce(combine, files)

    kwargs = {'sort_keys': True, 'indent': 4} if arguments.pretty else {}
    print json.dumps(result, **kwargs)