#!/usr/bin/env python3
"""Local JSON configuration teaching fixture. No network or system changes."""
import json,sys
if len(sys.argv)!=2:
 print('usage: python3 json_probe.py CONFIG.json');sys.exit(4)
try:
 with open(sys.argv[1],encoding='utf-8') as f: data=json.load(f)
except (OSError,json.JSONDecodeError) as e:
 print('PARSE ERROR:',e.__class__.__name__);sys.exit(2)
if not isinstance(data,dict):
 print('SHAPE ERROR: expected an object');sys.exit(3)
print('OK: object with',len(data),'keys')