simonw/check.md Secret

## check.md

      
    Raw
  

              check.md
            
          
    2025-03-26T00:16:57    conversation: 01jq7wzmsg985fsyffwz1w75db id: 01jq7wzmsnqtbewqf2jdmm2mad

Model: gemini-2.5-pro-exp-03-25
Prompt

Python CLI app to test if a URL has gzip and does ETags or conditinal GET last modified, no dependencies beyond standard library
Response

Okay, here's a Python CLI script that uses only the standard library (urllib, argparse, sys) to test a URL for gzip support and conditional GET capabilities (ETag and Last-Modified).
#!/usr/bin/env python3

import argparse
import sys
import urllib.request
import urllib.parse
import urllib.error
from http.client import HTTPMessage  # For type hinting response.info()

# --- Configuration ---
USER_AGENT = "Python-StdLib-HeaderCheck/1.0"

def check_url_features(url: str):
    """
    Performs checks on a given URL for Gzip, ETag, and Last-Modified support.

    Args:
        url: The URL string to test.

    Returns:
        None. Prints results to stdout. Exits with code 1 on critical errors.
    """
    print(f"[*] Testing URL: {url}")

    # --- Initial Request (Check for Gzip, ETag, Last-Modified) ---
    print("[*] Performing initial GET request...")
    initial_headers = {
        'Accept-Encoding': 'gzip',
        'User-Agent': USER_AGENT,
    }
    req_initial = urllib.request.Request(url, headers=initial_headers, method='GET')

    response_initial = None
    initial_info: HTTPMessage = None
    etag = None
    last_modified = None
    supports_gzip = False

    try:
        with urllib.request.urlopen(req_initial, timeout=10) as response:
            response_initial = response
            initial_info = response.info() # Headers object
            status_code = response.getcode()
            print(f"[+] Initial request successful (Status: {status_code})")

            # Check for Gzip support in response
            content_encoding = initial_info.get('Content-Encoding', '').lower()
            if 'gzip' in content_encoding:
                supports_gzip = True
                print("[+] Gzip: Supported (Server sent 'Content-Encoding: gzip')")
            else:
                print("[-] Gzip: Not detected in response headers.")

            # Extract ETag and Last-Modified for conditional requests
            etag = initial_info.get('ETag')
            last_modified = initial_info.get('Last-Modified')

            if etag:
                print(f"[+] ETag: Found ('{etag}')")
            else:
                print("[-] ETag: Header not found.")

            if last_modified:
                print(f"[+] Last-Modified: Found ('{last_modified}')")
            else:
                print("[-] Last-Modified: Header not found.")

            # Ensure response body is read and connection potentially closed/reused
            response.read()

    except urllib.error.HTTPError as e:
        print(f"[!] Initial Request Failed: HTTP Error {e.code} - {e.reason}", file=sys.stderr)
        # Optionally print headers even on error if available
        if e.headers:
           print("[!] Server response headers (on error):")
           print(e.headers)
        sys.exit(1)
    except urllib.error.URLError as e:
        print(f"[!] Initial Request Failed: URL Error - {e.reason}", file=sys.stderr)
        sys.exit(1)
    except Exception as e:
        print(f"[!] Initial Request Failed: An unexpected error occurred - {e}", file=sys.stderr)
        sys.exit(1)

    # --- Conditional GET Request (ETag) ---
    if etag:
        print("\n[*] Performing conditional GET request using ETag...")
        conditional_headers_etag = {
            'User-Agent': USER_AGENT,
            'If-None-Match': etag,
            'Accept-Encoding': 'gzip', # Keep consistent
        }
        req_conditional_etag = urllib.request.Request(url, headers=conditional_headers_etag, method='GET')

        try:
            with urllib.request.urlopen(req_conditional_etag, timeout=10) as response:
                # If we get here without a 304, the conditional GET didn't work as expected
                status_code = response.getcode()
                print(f"[-] ETag Conditional GET: Did not work as expected. Received Status {status_code} (expected 304).")
                response.read() # Consume body

        except urllib.error.HTTPError as e:
            if e.code == 304:
                print("[+] ETag Conditional GET: Worked! Received Status 304 (Not Modified).")
            else:
                print(f"[!] ETag Conditional GET: Failed. HTTP Error {e.code} - {e.reason}", file=sys.stderr)
        except urllib.error.URLError as e:
            print(f"[!] ETag Conditional GET: Failed. URL Error - {e.reason}", file=sys.stderr)
        except Exception as e:
            print(f"[!] ETag Conditional GET: Failed. An unexpected error occurred - {e}", file=sys.stderr)
    else:
        print("\n[*] Skipping ETag conditional GET (No ETag found in initial response).")


    # --- Conditional GET Request (Last-Modified) ---
    if last_modified:
        print("\n[*] Performing conditional GET request using Last-Modified...")
        conditional_headers_lm = {
            'User-Agent': USER_AGENT,
            'If-Modified-Since': last_modified,
            'Accept-Encoding': 'gzip', # Keep consistent
        }
        req_conditional_lm = urllib.request.Request(url, headers=conditional_headers_lm, method='GET')

        try:
            with urllib.request.urlopen(req_conditional_lm, timeout=10) as response:
                 # If we get here without a 304, the conditional GET didn't work as expected
                status_code = response.getcode()
                print(f"[-] Last-Modified Conditional GET: Did not work as expected. Received Status {status_code} (expected 304).")
                response.read() # Consume body

        except urllib.error.HTTPError as e:
            if e.code == 304:
                print("[+] Last-Modified Conditional GET: Worked! Received Status 304 (Not Modified).")
            else:
                print(f"[!] Last-Modified Conditional GET: Failed. HTTP Error {e.code} - {e.reason}", file=sys.stderr)
        except urllib.error.URLError as e:
            print(f"[!] Last-Modified Conditional GET: Failed. URL Error - {e.reason}", file=sys.stderr)
        except Exception as e:
            print(f"[!] Last-Modified Conditional GET: Failed. An unexpected error occurred - {e}", file=sys.stderr)
    else:
        print("\n[*] Skipping Last-Modified conditional GET (No Last-Modified header found in initial response).")

    # --- Final Summary ---
    print("\n--- Summary ---")
    print(f"URL: {url}")
    print(f"Gzip Supported by Server: {'Yes' if supports_gzip else 'No'}")
    print(f"ETag Header Present: {'Yes' if etag else 'No'}")
    if etag:
        # Note: This relies on the logic above printing the success/failure
        print(f"ETag Conditional GET (If-None-Match): Check log above for 304 status.")
    print(f"Last-Modified Header Present: {'Yes' if last_modified else 'No'}")
    if last_modified:
        # Note: This relies on the logic above printing the success/failure
        print(f"Last-Modified Conditional GET (If-Modified-Since): Check log above for 304 status.")
    print("-------------\n")


def main():
    """Parses arguments and runs the check."""
    parser = argparse.ArgumentParser(
        description="Check a URL for Gzip, ETag, and Last-Modified support using only Python's standard library.",
        formatter_class=argparse.ArgumentDefaultsHelpFormatter
    )
    parser.add_argument("url", help="The URL to test (e.g., https://www.example.com)")

    args = parser.parse_args()

    # Basic URL validation and scheme addition
    parsed_url = urllib.parse.urlparse(args.url)
    if not parsed_url.scheme:
        print(f"[!] URL '{args.url}' is missing a scheme (e.g., http:// or https://). Assuming 'http://'.", file=sys.stderr)
        url_to_test = f"http://{args.url}"
        # Re-parse to ensure validity after adding scheme
        parsed_url = urllib.parse.urlparse(url_to_test)
        if not parsed_url.netloc:
             print(f"[!] Invalid URL structure even after adding http://: '{url_to_test}'", file=sys.stderr)
             sys.exit(1)

    else:
         url_to_test = args.url
         if not parsed_url.netloc:
             print(f"[!] Invalid URL structure: '{url_to_test}'", file=sys.stderr)
             sys.exit(1)


    # Consider trying HTTPS first if no scheme was provided? For now, stick to HTTP default.
    # Or: try https first, if fails, try http? Might be too complex for stdlib only easily.

    check_url_features(url_to_test)


if __name__ == "__main__":
    main()
How to Use:


Save: Save the code above as a Python file (e.g., check_headers.py).


Make Executable (Optional): On Linux/macOS, you can make it directly executable: chmod +x check_headers.py.


Run: Execute it from your terminal, passing the URL as an argument:
# Using python explicitly
python check_headers.py https://www.google.com

# Or, if made executable:
./check_headers.py http://example.com

# Example without scheme (will default to http://)
./check_headers.py www.github.com


Explanation:

Standard Libraries: Imports only argparse, sys, urllib.request, urllib.parse, urllib.error, and http.client (for type hinting, not strictly required for functionality).
check_url_features(url) function:

Takes the URL string.
Initial Request:

Creates a urllib.request.Request object.
Sets the Accept-Encoding: gzip header to tell the server we can handle gzip.
Sets a basic User-Agent.
Uses urllib.request.urlopen() inside a with statement (ensures the connection is closed). A timeout is added for robustness.
Error Handling: Uses try...except blocks to catch HTTPError (like 404, 500) and URLError (like DNS lookup failure, connection refused). Exits on critical initial errors.
Gzip Check: Examines the Content-Encoding header from the response (response.info().get('Content-Encoding')).
Header Extraction: Retrieves ETag and Last-Modified headers if present.
response.read(): Reads the response body. This is important to ensure the connection state is managed correctly, even though we don't use the body content here.


Conditional GET (ETag):

Only runs if an ETag was found previously.
Creates a new Request object.
Adds the If-None-Match header with the ETag value.
Sends the request.
Checks for 304: The expected outcome for a successful conditional GET is an HTTPError with a status code of 304 Not Modified. If the request succeeds with a 200 status, it means the server sent the full content again, ignoring the ETag.


Conditional GET (Last-Modified):

Similar logic to the ETag check, but uses the If-Modified-Since header with the Last-Modified value.


Output: Prints informative messages during the process and a summary at the end.


main() function:

Uses argparse to define and parse the command-line url argument.
Performs basic URL validation using urllib.parse.urlparse and attempts to add http:// if no scheme is provided.
Calls check_url_features.


if __name__ == "__main__":: Standard Python practice to ensure main() is called only when the script is executed directly.

This script fulfills the requirements of using only the standard library while providing checks for the specified HTTP features.
Token usage:

28 input, 3,038 output, {"promptTokensDetails": [{"modality": "TEXT", "tokenCount": 28}]}
2025-03-26T00:22:07

Prompt

I do not like it telling me to check log above, it should check that for me
Response

Okay, you're right, that's much better user experience. The script should determine the success or failure of the conditional GETs itself.
Here's the updated version that explicitly checks the status code of the conditional requests and reports the outcome clearly in the summary:
#!/usr/bin/env python3

import argparse
import sys
import urllib.request
import urllib.parse
import urllib.error
from http.client import HTTPMessage  # For type hinting response.info()

# --- Configuration ---
USER_AGENT = "Python-StdLib-HeaderCheck/1.1" # Version bump

def check_url_features(url: str):
    """
    Performs checks on a given URL for Gzip, ETag, and Last-Modified support.

    Args:
        url: The URL string to test.

    Returns:
        None. Prints results to stdout. Exits with code 1 on critical errors.
    """
    print(f"[*] Testing URL: {url}")

    # --- State Variables ---
    supports_gzip = False
    etag = None
    last_modified = None
    etag_conditional_worked = None # None = N/A, False = Failed, True = Worked (304)
    last_modified_conditional_worked = None # None = N/A, False = Failed, True = Worked (304)

    # --- Initial Request (Check for Gzip, ETag, Last-Modified) ---
    print("[*] Performing initial GET request...")
    initial_headers = {
        'Accept-Encoding': 'gzip',
        'User-Agent': USER_AGENT,
    }
    req_initial = urllib.request.Request(url, headers=initial_headers, method='GET')

    try:
        with urllib.request.urlopen(req_initial, timeout=15) as response: # Increased timeout slightly
            initial_info = response.info() # Headers object
            status_code = response.getcode()
            print(f"[+] Initial request successful (Status: {status_code})")

            # Check for Gzip support in response
            content_encoding = initial_info.get('Content-Encoding', '').lower()
            if 'gzip' in content_encoding:
                supports_gzip = True
                print("[+] Gzip: Supported (Server sent 'Content-Encoding: gzip')")
            else:
                print("[-] Gzip: Not detected in response headers.")

            # Extract ETag and Last-Modified for conditional requests
            etag = initial_info.get('ETag')
            last_modified = initial_info.get('Last-Modified')

            if etag:
                print(f"[+] ETag: Found ('{etag}')")
            else:
                print("[-] ETag: Header not found.")

            if last_modified:
                print(f"[+] Last-Modified: Found ('{last_modified}')")
            else:
                print("[-] Last-Modified: Header not found.")

            # Ensure response body is read and connection potentially closed/reused
            response.read()

    except urllib.error.HTTPError as e:
        print(f"[!] Initial Request Failed: HTTP Error {e.code} - {e.reason}", file=sys.stderr)
        if e.headers:
           print("[!] Server response headers (on error):")
           print(e.headers)
        sys.exit(1)
    except urllib.error.URLError as e:
        print(f"[!] Initial Request Failed: URL Error - {e.reason}", file=sys.stderr)
        sys.exit(1)
    except Exception as e:
        print(f"[!] Initial Request Failed: An unexpected error occurred - {e}", file=sys.stderr)
        sys.exit(1)

    # --- Conditional GET Request (ETag) ---
    if etag:
        print("\n[*] Performing conditional GET request using ETag...")
        etag_conditional_worked = False # Assume failure unless we get 304
        conditional_headers_etag = {
            'User-Agent': USER_AGENT,
            'If-None-Match': etag,
            'Accept-Encoding': 'gzip',
        }
        req_conditional_etag = urllib.request.Request(url, headers=conditional_headers_etag, method='GET')

        try:
            with urllib.request.urlopen(req_conditional_etag, timeout=10) as response:
                status_code = response.getcode()
                # If we get here without a 304, the conditional GET didn't work as expected
                print(f"[-] ETag Conditional GET: Did not work as expected. Received Status {status_code} (expected 304). Server sent full response.")
                response.read() # Consume body

        except urllib.error.HTTPError as e:
            if e.code == 304:
                print("[+] ETag Conditional GET: Worked! Received Status 304 (Not Modified).")
                etag_conditional_worked = True
            else:
                print(f"[!] ETag Conditional GET: Failed. Server responded with HTTP Error {e.code} - {e.reason}", file=sys.stderr)
        except urllib.error.URLError as e:
            print(f"[!] ETag Conditional GET: Request failed. URL Error - {e.reason}", file=sys.stderr)
        except Exception as e:
            print(f"[!] ETag Conditional GET: Request failed. An unexpected error occurred - {e}", file=sys.stderr)
    else:
        print("\n[*] Skipping ETag conditional GET (No ETag found in initial response).")
        # etag_conditional_worked remains None


    # --- Conditional GET Request (Last-Modified) ---
    if last_modified:
        print("\n[*] Performing conditional GET request using Last-Modified...")
        last_modified_conditional_worked = False # Assume failure unless we get 304
        conditional_headers_lm = {
            'User-Agent': USER_AGENT,
            'If-Modified-Since': last_modified,
            'Accept-Encoding': 'gzip',
        }
        req_conditional_lm = urllib.request.Request(url, headers=conditional_headers_lm, method='GET')

        try:
            with urllib.request.urlopen(req_conditional_lm, timeout=10) as response:
                status_code = response.getcode()
                 # If we get here without a 304, the conditional GET didn't work as expected
                print(f"[-] Last-Modified Conditional GET: Did not work as expected. Received Status {status_code} (expected 304). Server sent full response.")
                response.read() # Consume body

        except urllib.error.HTTPError as e:
            if e.code == 304:
                print("[+] Last-Modified Conditional GET: Worked! Received Status 304 (Not Modified).")
                last_modified_conditional_worked = True
            else:
                print(f"[!] Last-Modified Conditional GET: Failed. Server responded with HTTP Error {e.code} - {e.reason}", file=sys.stderr)
        except urllib.error.URLError as e:
            print(f"[!] Last-Modified Conditional GET: Request failed. URL Error - {e.reason}", file=sys.stderr)
        except Exception as e:
            print(f"[!] Last-Modified Conditional GET: Request failed. An unexpected error occurred - {e}", file=sys.stderr)
    else:
        print("\n[*] Skipping Last-Modified conditional GET (No Last-Modified header found).")
        # last_modified_conditional_worked remains None

    # --- Final Summary ---
    print("\n--- Summary ---")
    print(f"URL: {url}")
    print(f"Gzip Supported by Server: {'Yes' if supports_gzip else 'No'}")
    print(f"ETag Header Present: {'Yes' if etag else 'No'}")
    if etag:
        print(f"ETag Conditional GET Works (Returns 304): {'Yes' if etag_conditional_worked else 'No'}")
    else:
         print(f"ETag Conditional GET Works (Returns 304): N/A")

    print(f"Last-Modified Header Present: {'Yes' if last_modified else 'No'}")
    if last_modified:
       print(f"Last-Modified Conditional GET Works (Returns 304): {'Yes' if last_modified_conditional_worked else 'No'}")
    else:
       print(f"Last-Modified Conditional GET Works (Returns 304): N/A")
    print("-------------\n")


def main():
    """Parses arguments and runs the check."""
    parser = argparse.ArgumentParser(
        description="Check a URL for Gzip, ETag, and Last-Modified support using only Python's standard library.",
        formatter_class=argparse.ArgumentDefaultsHelpFormatter
    )
    parser.add_argument("url", help="The URL to test (e.g., https://www.example.com)")

    args = parser.parse_args()

    # Basic URL validation and scheme addition
    parsed_url = urllib.parse.urlparse(args.url)
    if not parsed_url.scheme:
        # Try https first if no scheme provided, fall back to http if needed?
        # For simplicity now, just default to http and warn.
        print(f"[!] URL '{args.url}' is missing a scheme (e.g., http:// or https://). Assuming 'http://'.", file=sys.stderr)
        url_to_test = f"http://{args.url}"
        parsed_url = urllib.parse.urlparse(url_to_test) # Re-parse
        if not parsed_url.netloc:
             print(f"[!] Invalid URL structure even after adding http://: '{url_to_test}'", file=sys.stderr)
             sys.exit(1)

    else:
         url_to_test = args.url
         if not parsed_url.netloc:
             print(f"[!] Invalid URL structure: '{url_to_test}'", file=sys.stderr)
             sys.exit(1)

    check_url_features(url_to_test)


if __name__ == "__main__":
    main()
Changes:

State Variables: Introduced etag_conditional_worked and last_modified_conditional_worked. They are initialized to None.
Conditional Logic Update:

Before making a conditional request (if the relevant header exists), the corresponding state variable is set to False (assuming failure).
If the request results in an HTTPError with e.code == 304, the state variable is set to True.
If the request succeeds with a 200 status (meaning the server ignored the condition and sent the full response), the state variable remains False.
If any other error occurs during the conditional request, the state variable remains False.


Summary Update:

The summary now checks the value of etag_conditional_worked and last_modified_conditional_worked.
It prints "Yes" if the value is True.
It prints "No" if the value is False.
It prints "N/A" if the corresponding header (ETag or Last-Modified) wasn't present in the initial request (meaning the conditional check wasn't performed, and the state variable is still None).


Now the summary provides a direct answer about whether the conditional GET mechanism worked for each header type found.
Token usage:

3,094 input, 2,666 output, {"promptTokensDetails": [{"modality": "TEXT", "tokenCount": 3094}]}