Add useful CLI utilities and smoke tests for validation

useful_programs/README.md

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+# Useful Programs
+
+Small collection of handy CLI utilities.
+
+Files:
+- `cli_calculator.py` — safe arithmetic evaluator
+- `file_organizer.py` — move files into folders by extension
+- `json_pretty.py` — pretty-print JSON from file or stdin
+- `simple_http_server.py` — serve current directory over HTTP
+- `smoke_test.py` — quick checks to verify the scripts run
+
+Usage examples:
+
+python cli_calculator.py "(2+3)*4"
+python file_organizer.py /path/to/folder
+cat file.json | python json_pretty.py
+python simple_http_server.py 8080

useful_programs/cli_calculator.py

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+#!/usr/bin/env python3
+"""Simple CLI calculator: supports + - * / and parentheses via eval with safety."""
+import ast
+import operator as op
+import sys
+
+ALLOWED_OPERATORS = {
+    ast.Add: op.add,
+    ast.Sub: op.sub,
+    ast.Mult: op.mul,
+    ast.Div: op.truediv,
+    ast.Pow: op.pow,
+    ast.USub: op.neg,
+}
+
+
+def eval_expr(expr: str):
+    """Safely evaluate a math expression using AST."""
+    def _eval(node):
+        if isinstance(node, ast.Num):
+            return node.n
+        if isinstance(node, ast.UnaryOp) and type(node.op) in ALLOWED_OPERATORS:
+            return ALLOWED_OPERATORS[type(node.op)](_eval(node.operand))
+        if isinstance(node, ast.BinOp) and type(node.op) in ALLOWED_OPERATORS:
+            return ALLOWED_OPERATORS[type(node.op)](_eval(node.left), _eval(node.right))
+        raise ValueError(f"Unsupported expression: {ast.dump(node)}")
+
+    parsed = ast.parse(expr, mode="eval")
+    return _eval(parsed.body)
+
+
+def main():
+    if len(sys.argv) > 1:
+        expr = " ".join(sys.argv[1:])
+    else:
+        expr = input("Enter expression: ")
+    try:
+        result = eval_expr(expr)
+        print(result)
+    except Exception as e:
+        print("Error:", e)
+
+
+if __name__ == "__main__":
+    main()

useful_programs/file_organizer.py

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+#!/usr/bin/env python3
+"""Organize files in a directory into subfolders by extension.
+
+Usage: python file_organizer.py [target_dir]
+"""
+import os
+import shutil
+import sys
+
+
+def organize(target_dir: str):
+    if not os.path.isdir(target_dir):
+        raise ValueError(f"Not a directory: {target_dir}")
+    for entry in os.listdir(target_dir):
+        full = os.path.join(target_dir, entry)
+        if os.path.isfile(full):
+            _, ext = os.path.splitext(entry)
+            ext = ext[1:].lower() or "no_ext"
+            dest_dir = os.path.join(target_dir, ext)
+            os.makedirs(dest_dir, exist_ok=True)
+            shutil.move(full, os.path.join(dest_dir, entry))
+
+
+def main():
+    target = sys.argv[1] if len(sys.argv) > 1 else os.getcwd()
+    organize(target)
+    print(f"Organized files in {target}")
+
+
+if __name__ == "__main__":
+    main()

useful_programs/json_pretty.py

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+#!/usr/bin/env python3
+"""Read JSON from a file or stdin and pretty-print it."""
+import json
+import sys
+
+
+def main():
+    if len(sys.argv) > 1:
+        path = sys.argv[1]
+        with open(path, "r", encoding="utf-8") as f:
+            data = json.load(f)
+    else:
+        data = json.load(sys.stdin)
+    print(json.dumps(data, indent=2, ensure_ascii=False))
+
+
+if __name__ == "__main__":
+    main()

useful_programs/simple_http_server.py

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+#!/usr/bin/env python3
+"""Start a simple HTTP server serving the current directory.
+
+Usage: python simple_http_server.py [port]
+"""
+import http.server
+import socketserver
+import sys
+
+
+def main():
+    port = int(sys.argv[1]) if len(sys.argv) > 1 else 8000
+    handler = http.server.SimpleHTTPRequestHandler
+    with socketserver.TCPServer(("", port), handler) as httpd:
+        print(f"Serving HTTP on 0.0.0.0:{port} (Ctrl-C to stop)")
+        try:
+            httpd.serve_forever()
+        except KeyboardInterrupt:
+            print("\nServer stopped")
+
+
+if __name__ == "__main__":
+    main()

useful_programs/smoke_test.py

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+#!/usr/bin/env python3
+"""Run quick smoke tests for the useful_programs utilities."""
+import subprocess
+import sys
+import json
+from pathlib import Path
+
+
+ROOT = Path(__file__).parent
+
+
+def run(cmd, input_text=None):
+    p = subprocess.run([sys.executable, *cmd], input=input_text, text=True, capture_output=True)
+    return p.returncode, p.stdout, p.stderr
+
+
+def test_calc():
+    code, out, err = run([str(ROOT / "cli_calculator.py"), "(2+3)*4"])
+    assert code == 0 and out.strip() == "20"
+
+
+def test_json():
+    js = '{"a":1, "b":[1,2]}'
+    code, out, err = run([str(ROOT / "json_pretty.py")], input_text=js)
+    assert code == 0
+    data = json.loads(out)
+    assert data["a"] == 1
+
+
+def test_file_organizer(tmp_dir: Path):
+    d = tmp_dir / "test_org"
+    d.mkdir(exist_ok=True)
+    f = d / "sample.txt"
+    f.write_text("hello")
+    code, out, err = run([str(ROOT / "file_organizer.py"), str(d)])
+    assert code == 0
+    assert (d / "txt" / "sample.txt").exists()
+
+
+def main():
+    print("Running smoke tests...")
+    test_calc()
+    print("calc ok")
+    test_json()
+    print("json ok")
+    # file organizer needs a temp dir; create one in /tmp
+    from tempfile import TemporaryDirectory
+    from pathlib import Path
+    with TemporaryDirectory() as td:
+        test_file_organizer(Path(td))
+    print("file organizer ok")
+    print("All smoke tests passed")
+
+
+if __name__ == "__main__":
+    main()