butiran

reg npprel-protocol

· 3 mins read

Previous approach to launch a Hugo post via link in a HTML page hosted locally is still inconvenient due to absolute path to the file 1. Here better approach is reported as sugggested in a discussion with GPT-5 2. Steps to create own URL Protocol in Windows seems obvious 3, but not for me until today.

demo

As example edit this post. Click no the link edit will open Notepad++ editing the post.

shortcode

Content of link/npprel.html in layouts/shortcodes/ is as follow

<a href="npprel:///{{ .Get 0 }}">{{ if .Get 1 }}{{ .Get 1 }}{{ else }}edit{{ end }}</a>

and

{{< link/npprel "25/i/67-reg-npprel-protocol.md" "edit" >}}

is how to use it.

handler

Content of npprel.py in setup/npprel/ is as follow

import os, sys, subprocess, urllib.parse

# --- Notepad++ path per machine ---
NOTEPADPP = r"C:\Program Files\Notepad++\notepad++.exe"

# This script is in <repo>\setup\npprel\npprel.py
script_dir = os.path.dirname(os.path.abspath(__file__))

# repo root is two levels up
repo_root = os.path.abspath(os.path.join(script_dir, os.pardir, os.pardir))

if len(sys.argv) < 2:
    sys.exit("Usage: npprel.py <url>")

url = sys.argv[1]  # e.g. npprel://content/post/my-post.md
parsed = urllib.parse.urlparse(url)
rel_path = urllib.parse.unquote(parsed.path).lstrip("/")
folder_path = "content/posts/"
full_path = os.path.normpath(os.path.join(repo_root, folder_path, rel_path))

print(full_path)

if not os.path.exists(full_path):
    subprocess.run([NOTEPADPP])  # just open N++ if missing
else:
    subprocess.run([NOTEPADPP, full_path])

and it will be called when npprel:// url protocol is clicked in a HTML file.

installer

Content of install-npprel.bat in setup/ is as follow

@echo off
echo Installing npprel:// protocol handler...

REM Use Python in the standard user path
set PYTHON_PATH=%LOCALAPPDATA%\Programs\Python\Python312\python.exe
set SCRIPT_PATH=%~dp0npprel.py

REM Build a temporary reg file with correct paths
set TMPREG=%TEMP%\npprel.reg

REM Escape backslashes for .reg
set "PYTHON_PATH_ESC=%PYTHON_PATH:\=\\%"
set "SCRIPT_PATH_ESC=%SCRIPT_PATH:\=\\%"

(
echo Windows Registry Editor Version 5.00
echo.
echo [HKEY_CURRENT_USER\Software\Classes\npprel]
echo @="URL:npprel Protocol"
echo "URL Protocol"=""
echo.
echo [HKEY_CURRENT_USER\Software\Classes\npprel\shell\open\command]
echo @="\"%PYTHON_PATH_ESC%\" \"%SCRIPT_PATH_ESC%\" \"%%1\""
) > "%TMPREG%"

reg import "%TMPREG%"

echo.
echo npprel:// protocol installed.
pause

where it should be executed to add npprel:// url protocol to Windows registry.

Steps

Following are steps to enable npprel:// url protocol in a HTML page generated from a Hugo post.

  1. Create a folder setup/npprel/.
  2. Inside it add install-npprel.bat and npprel.py.
  3. Run install-npprel.bat to create a temporary .reg file and import it to register the npprel:// protocol.
  4. Create a shortcode file link/npprel.html in your Hugo project.
  5. Use that shortcode in a Hugo post to insert a npprel:// link.
  6. Run hugo to build the site.
  7. Open the generated HTML page from the post.
  8. Click the npprel:// link to launch your handler script.

Original version and full explanation of the steps is available 4.

to-do

  • Perform a pull request in another machine to test whether it also works.
  • Add note to previous note about npp:// protocol that will be kept only for historical purpose.
  • Create a Medium story about this note.

refs

  1. Sparisoma Viridi, “reg npp protocol”, butiran, 21 Sep 2025, url https://dudung.github.io/butiran/25i66/ [20250921]. ↩︎

  2. GPT-5, “Fix Hugo path issue for npprel”, ChatGPT, 21 Sep 2025, url https://chatgpt.com/share/68cfba4b-4730-800a-88ab-44efb3042440 [20250921]. ↩︎

  3. Avinash Tare, “How to create own URL Protocol In Windows”, DEV Community, 6 Aug 2024, url https://dev.to/avinash_tare/how-to-create-own-url-protocol-in-windows-42bj [20250921]. ↩︎

  4. GPT-5, “Register custom URL protocol”, ChatGPT, 21 Sep 2025, url https://chatgpt.com/share/68cfeaf9-03d0-800a-bb07-149118c5ac24 [20250921]. ↩︎