Mahmud Ridwan (hjr265) on hjr265.me

Papyrus

m@hjr265.me (Mahmud Ridwan) — Tue, 23 Feb 2016 00:00:00 +0000

Papyrus is a real-time collaborative Markdown editor and document repository with simple organization and project-based management. Built during GopherGala 2016, it features operational transformation for conflict-free concurrent editing.

Toph

m@hjr265.me (Mahmud Ridwan) — Wed, 01 Apr 2015 00:00:00 +0000

Toph is the leading competitive programming platform in Bangladesh. Top institutions have hosted all noteworthy Bangladeshi programming contests on Toph since 2015.

CodeMarshal

m@hjr265.me (Mahmud Ridwan) — Wed, 01 Aug 2012 00:00:00 +0000

CodeMarshal is a programming contest hosting platform. The platform successfully hosted the preliminary mock, preliminary, live, and semi-live contests of ACM ICPC 2014 Dhaka Regional.

I built CodeMarshal while employed at Mukto Software under the leadership of then Chairman and CEO Mahmudur Rahman.

Redsync

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Redsync is a Redis-based distributed lock implementation in Go. It is also mentioned on the official Redis website as a reference Go implementation of the Redlock algorithm.

Drafts

m@hjr265.me (Mahmud Ridwan) — Wed, 01 Apr 2015 00:00:00 +0000

Drafts is an all-in-one tool for designing and testing programming problems.

Bullet

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Bullet is a fast Twelve-Factor application deploy tool. Bullet deploys your application over SSH and runs it within Docker. You can configure the environment of your application by specifying per-process Dockerfiles/images.

Cactus

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Cactus is a modern, lightweight programming contest control system in a single binary. Deploying it is as simple as downloading its binary to a server on the local network. In some ways, Cactus is the precursor to Toph.

Node WHOIS

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Node WHOIS is a WHOIS client for Node.js.

Trace

m@hjr265.me (Mahmud Ridwan) — Wed, 01 Jan 2025 00:00:00 +0000

Trace is an interactive algorithm visualizer. It provides step-by-step animated visualizations for algorithms and data structures across graph theory, number theory, search, and sorting, with annotated source code that highlights in sync with each execution step.

μTools

m@hjr265.me (Mahmud Ridwan) — Wed, 01 Jan 2025 00:00:00 +0000

μTools is a developer utility suite built with Rust and GPUI. It provides quick access to commonly needed conversion and formatting tools, including Base64 and HTML encoding/decoding, Unix timestamp conversion, JSON formatting, text diffing, and more.

CodeMirror LanguageServer

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

This is a CodeMirror 6 plugin to enable code completion, hover tooltips, and linter functionality by connecting the editor with a language server over WebSocket.

Loadcat

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Loadcat is an Nginx configurator that allows you to use Nginx as a load balancer.

GitTop

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Mar 2026 00:00:00 +0000

GitTop is an htop-like TUI dashboard for Git repositories. It provides seven pages of insights: summary with braille charts, activity heatmaps, contributor rankings, branch comparisons, file statistics, release timelines, and a scrollable commit log with diff viewer and fuzzy search. It also includes a filter DSL for structured queries like author:"alice" and path:*.go.

Printd

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Printd is a print server daemon for Toph contests. It runs on a computer connected to a printer and lets contest participants request physical prints directly from the platform, generating PDFs with customized headers before sending them to the printer.

Scanlib

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Scanlib is a metaparser that validates input files and generates input code in different programming languages.

Too

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Too is a collaborative memory-based recommendation engine implementation in Go built on top of Redis and simple set mathematics.

Brdgd

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Brdgd is a WebRTC-based file transfer tool.

Dots

m@hjr265.me (Mahmud Ridwan) — Sun, 01 Jan 2006 00:00:00 +0000

Dots is a simple DNS toolkit.

Now

m@hjr265.me (Mahmud Ridwan) — Mon, 23 Mar 2026 00:00:00 +0600

Software Engineer in Dhaka, Bangladesh 🇧🇩

Family
Software Engineer / CEO at Furqan Software — Sep ‘15 - present
- Spending as much time as I can crafting Toph, the premier Bangladeshi sport programming platform
Freelance software engineer
- Networks: Toptal and Upwork
- Strong Suits: Go, TypeScript, JavaScript, Node.js, Rust, Python, React, Svelte, PostgreSQL, MongoDB, Redis, RabbitMQ, Docker, Terraform, Ansible
- Building a geospatial intelligence platform for a client, through Toptal
- Helping revamp a disability-focused social & activity application for a client, through Toptal
Maintaining open-source projects
Reading Begum Khaleda Zia: Her Life, Her Story by Mahfuz Ullah

Can AI Take a Software Engineer's Job?

m@hjr265.me (Mahmud Ridwan) — Thu, 19 Mar 2026 20:20:00 +0600

I had an interesting exchange with a coding agent this evening.

Are coding agents useful? Absolutely. But can it take a software engineer’s job? You tell me.

Me: In .gitlab-ci.yml, can we set the workflow name only if the PLAYBOOK variable is set?

AI:

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workflow:
 name: "Playbook ${PLAYBOOK}"
 rules:
 - if: $PLAYBOOK != ""
 - when: always

The workflow.name only takes effect when matched by a rule, so on push pipelines (where $PLAYBOOK is empty) it falls through to when: always which uses the default pipeline name. When $PLAYBOOK is set, it shows e.g. “shape playbook”.

My First Fully Agentic Coding Project: GitTop

m@hjr265.me (Mahmud Ridwan) — Sat, 14 Mar 2026 14:20:00 +0600

I have been running Toph for over ten years. Somewhere along the way, I started wondering: what hours of the day do I actually work on it?

Commit timestamps felt like the right place to look. A quick one-off script could answer the question, and there are Git stats tools that spit out HTML reports. But I thought: this could be a good excuse to build a TUI application. Something like htop, but for a Git repository instead of system metrics.

Resurrecting a 12-Year-Old Node.js Project With Claude Code

m@hjr265.me (Mahmud Ridwan) — Sat, 07 Mar 2026 17:30:00 +0600

This weekend, I set out to get some high-resolution screenshots of zebra-algo (you may remember it as the now-defunct CodeMarshal or algo.codemarshal.org). My motivation was to document its design and features, as zebra-algo is a competitive programming contest platform I built back in 2014.

The plan was straightforward: run it locally, open it in a browser, take the screenshots, and be done.

Simple, except the codebase is twelve years old, making things tricky.

Ditching MongoDB Text Indexes for Edge N-Grams

m@hjr265.me (Mahmud Ridwan) — Mon, 02 Mar 2026 11:00:00 +0600

I like software that just works. If I type “North South” into a search box, I expect to find “North South University”. But if I type “North So”, I should still find it. Maybe not at the top, but it should be there.

For a while, Toph’s institution search did not work that way.

The Problem With MongoDB Text Indexes

The original implementation used a MongoDB text index on the name field. It is the obvious first choice. MongoDB makes it easy to set up, and for simple use cases, it works fine.

Strangest AMD Ryzen 7950x Bug

m@hjr265.me (Mahmud Ridwan) — Sat, 08 Mar 2025 19:20:00 +0600

I upgraded my primary computer to the AMD AM5 platform sometime in mid-2023. Before the upgrade, I had been using an Intel Core i7 4790 with 32 GB of RAM for about a decade. For the upgrade, I went with an AMD Ryzen 7950x with 128 GB of RAM. Given that my work lately has started to involve a lot of virtual machines, this upgrade was worth every bit.

However, the upgrade came with a few annoyances. One of them, and the worst one, in my opinion, was random reboots.

All Our Customer Care Agents Are Busy at This Moment

m@hjr265.me (Mahmud Ridwan) — Thu, 19 Sep 2024 19:15:00 +0600

It was the second week of August 2024. We realized that the television in our family space had suddenly stopped working. It would start, flash blue for a moment, and restart.

If we left it running for a while, the boot logo would appear with parts of the panel garbled.

This was no cheap, no-name, no-brand “smart” TV—at least that is what the salesperson told us when we bought it. It was a well-known brand.

How Hard Can It Be: Use JavaScript to Close Web Browser Window After Print

m@hjr265.me (Mahmud Ridwan) — Thu, 09 May 2024 12:00:00 +0600

So here is a simple JavaScript task I had to tackle for Toph:

When a user clicks the Print button, open a new tab/window and activate the print dialog. Close the window when the user confirms the print or cancels the dialog.

Attempt 1: Call `window.close()` Immediately After `window.print()`

I used the onclick attribute on the Print button to open the page to be printed on a new tab/window.

Remmina SPICE SSH Tunnel Bug and a Workaround

m@hjr265.me (Mahmud Ridwan) — Mon, 15 Jan 2024 19:45:00 +0600

I seem to come across the strangest of bugs.

Bug

Remmina SPICE over an SSH tunnel fails to handle keyboard-mouse interactions.

I have set up several virtual machines with desktop operating systems using Libvirt on my primary computer. I can access these virtual machines over the network using Libvirt on my laptop. However, I wanted to use Remmina as the SPICE client since it is more configurable.

All worked well until I tried to access a Manjaro Gnome virtual machine with the SSH tunnel feature on Remmina.

#100DaysToOffload Milestone: The 100th Blog Post

m@hjr265.me (Mahmud Ridwan) — Thu, 23 Nov 2023 14:00:00 +0600

And one hundred.

I have posted 100 blog posts in the last 365 days.

Why? Because I took on this #100DaysToOffload Internet challenge.

My brain, trained on decades of video games, is tuned to enjoy challenges, no questions asked.

But this challenge is very different from those social media challenges that die as fast as they become popular. How?

First, the #100DaysToOffload challenge is not as popular. At least, it is not as popular as it should be.

Android Emulator Slow As a Snail; Reason BTRFS

m@hjr265.me (Mahmud Ridwan) — Thu, 23 Nov 2023 10:00:00 +0600

I have been writing software professionally for over a decade. I have been writing software for even longer than that.

This week was the first time I wrote an Android program. Some journey it was. But that is a story for another day.

Today, in this blog post, I want to share a strange issue I encountered with Android Emulator and a fix.

If you are using BTRFS, you probably have copy-on-write (COW) enabled for the files on it. If your Android Emulator boot cache is on a BTRFS partition, you will notice the emulator running as slow as a snail.

Check If a WireGuard Connection Is Up

m@hjr265.me (Mahmud Ridwan) — Tue, 21 Nov 2023 15:55:00 +0600

I have several scripts and automation on my primary computer at home that can run when connected to the local area network of my workspace through a WireGuard connection.

These scripts are for routine tasks for my servers at my workspace, like backing them up to remote storage.

When the WireGuard connection is not running, the scripts fail at different points.

I wanted the scripts to fail right when they start if the WireGuard connection is not running.

Scanning a Website for Broken Links in Go

m@hjr265.me (Mahmud Ridwan) — Mon, 20 Nov 2023 23:15:00 +0600

Yes, I know there are paid and free tools for doing this. And yes, I know there are tools for this that I can run locally.

But this exercise allowed me to try out the well-designed Go package github.com/gocolly/colly.

Colly is a web scraping framework for Go.

Here is how I used it to quickly scan my website (the one you are on right now) for broken links.

First I defined a type for links to check and the URL of the page they appear on:

When Was the Last Time Technology Blew Your Mind?

m@hjr265.me (Mahmud Ridwan) — Sun, 19 Nov 2023 16:30:00 +0600

I read a blog post by Kev Quirk this morning.

When Was the Last Time Tech Blew Your Mind?

It was a refreshing read.

The world has come a long way as far as technology is concerned. But I think somewhere along the lines, the definition of innovation changed.

I upgraded my desktop computer a couple of months ago.

Before the upgrade, I used an Intel CPU from 2014 with as much RAM as the platform could handle. It was working fine. But I needed a few extra CPU cores and more RAM. So, I got a top-of-the-line AMD Ryzen CPU.

Go Web Server for Remotely Powering on a Desktop Computer With a Raspberry Pi

m@hjr265.me (Mahmud Ridwan) — Sat, 18 Nov 2023 16:40:00 +0600

Last month, I wrote a blog post on how to use a Raspberry Pi and a 5V 2-channel relay to remotely power on or reset a desktop computer.

Powering on a Desktop Computer Remotely With a Raspberry Pi

To keep the blog post simple, I used the gpio command to interact with the GPIO pins on the Raspberry Pi.

That works well. But by deploying a little web server you can have an easier user interface to power on or reset your desktop computer remotely.

7 Useful io.Reader and io.Writer Wrappers in Go

m@hjr265.me (Mahmud Ridwan) — Fri, 17 Nov 2023 09:45:00 +0600

Whenever I think about Go in comparison to other programming languages, the first thing that comes to my mind is how Go simplifies the concepts around concurrency and writing concurrent programs.

After all, concurrency is one of the features touted on the homepage:

Built-in concurrency and a robust standard library

But there is something else that Go simplifies and makes it very easy to wrap one’s head around.

The type system.

Forwarding a Port Over SSH in Go

m@hjr265.me (Mahmud Ridwan) — Thu, 16 Nov 2023 12:50:00 +0600

In the day and age where Kubernetes is the go-to tool for orchestrating your applications on the cloud, I have been spending time building Bullet. I enjoy working on this tool, building out features for it little by little. And it also allows me to learn so many details.

For example I just added the ability to forward ports from the remote server to the local over SSH. Bullet, being built using Go, I had to figure out how to forward a port over SSH in Go.

Strange Hugo Bug and How to Work Around It

m@hjr265.me (Mahmud Ridwan) — Wed, 15 Nov 2023 10:45:00 +0600

I was about to deploy my site with the latest blog post this morning and found Hugo broken. Or, my Hugo config.toml is broken. It depends on how you want to look at it.

I ran hugo deploy and bam! I see an internal template error.

ERROR render of "taxonomy" failed: template: _internal/_default/rss.xml:3:9: executing "_internal/_default/rss.xml" at <site>: can't evaluate field email in type string

According to pacman, the package manager on Arch Linux, I received an update for Hugo yesterday.

Serving JSON in Go with http.ServeContent

m@hjr265.me (Mahmud Ridwan) — Wed, 15 Nov 2023 10:00:00 +0600

I know many will start with something like Gin whenever they are working on a JSON/HTTP-based backend in Go.

I, not entirely sure if the minority, try to stick to Go’s built-in net/http package and, at most, use Gorilla Mux in most of my Go projects.

And so serving something simple like JSON is no different from the package’s point of view as any other content type: whatever it is, write it out to the w, the http.ResponseWriter.

Editing an SVG Icon to Be Resize-friendly

m@hjr265.me (Mahmud Ridwan) — Tue, 14 Nov 2023 10:00:00 +0600

This blog post is about something that I think I have absolutely no expertise in: graphics. But that also makes exploring this field and the aha moments much more rewarding.

A few weeks ago, I was working on adding an icon to the Toph Printd executable. I started to look for a suitable vector image on a paid vector icon and sticker repository I subscribe to.

I found one that I liked.

Testing a Go Package That Depends on Redis

m@hjr265.me (Mahmud Ridwan) — Mon, 13 Nov 2023 13:45:00 +0600

Redsync, one of my open-source Go packages, implements a distributed lock using Redis. It is an implementation of the Redlock algorithm.

This Go package has tests that run against multiple real Redis servers. And it is an example of how you can use the TestMain function to customize your Go tests.

The TestMain function, if defined in your Go tests, will allow you to run the Go code before and after the actual tests, which is really ideal for setup and teardown work.

Tracking io.Copy Progress in Go

m@hjr265.me (Mahmud Ridwan) — Sun, 12 Nov 2023 09:45:00 +0600

If you are writing Go code for any period, you must have used the io.Copy function. It takes an io.Writer and an io.Reader and copies everything from the reader to the writer until it reaches the end of file (EOF).

The function returns the number of bytes copied and an error (if any, other than io.EOF).

But this function blocks until the copy completes. How do you track the progress of io.Copy?

Responsive Activity Chart With Chart.js

m@hjr265.me (Mahmud Ridwan) — Sat, 11 Nov 2023 10:00:00 +0600

A few weeks ago I worked on improving the activity chart shown on Toph profiles.

Among adding legends and tweaking the look and feel of the chart, I paid some attention to how the chart behaves in terms of responsiveness.

Chart.js has built-in responsive features. But in this case, it meant the chart would scale as a whole. What I wanted instead is for the number of columns to increase/decrease depending on the space available.

Multi-threaded Downloads in Go

m@hjr265.me (Mahmud Ridwan) — Thu, 09 Nov 2023 14:00:00 +0600

The word multi-threaded here is an artifact of how download managers in the past worked.

The idea is to download a large file in parts, in parallel, over multiple TCP streams at once. In certain circumstances this can speed up the download significantly.

Let’s start with a naive way of downloading a file in Go:

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// Error handling omitted for brevity.

// Perform a GET request.
resp, _ := http.Get(url)
defer resp.Body.Close()

// Create the output file.
f, _ := os.Create("output.ext")

// Copy from the response body to the file.
io.Copy(f, resp.Body)
f.Close()

The code above is downloading the entire file in a single stream.

Building Advanced Search With Go and MongoDB

m@hjr265.me (Mahmud Ridwan) — Tue, 07 Nov 2023 13:00:00 +0600

I like software that allows advanced search. Advanced search is where you can use flags to indicate what you want.

Take email software as an example.

It may allow you to enter from:Bloo to:Mac subject:Imagination and find all emails that were sent from Bloo to Mac and has the word “Imagination” in the subject line.

But how do you implement something like this in Go? That is what this blog post is about.

Backing up Self-hosted GitLab With Ansible

m@hjr265.me (Mahmud Ridwan) — Mon, 06 Nov 2023 12:00:00 +0600

I have been making software for over a decade now. And one thing I have learned to love through this is automation.

After all, it is only a programmer who will spend hours automating a task that takes a few minutes to do.

There are good reasons for this.

I have a self-hosted GitLab instance for Furqan Software. And if you are self-hosting tools and services, the critical thing to do after ensuring security is automating backups.

JavaScript window.close Won't Close the Window

m@hjr265.me (Mahmud Ridwan) — Sat, 04 Nov 2023 19:00:00 +0600

I learned something new today.

In JavaScript within the web browser, window.close will not close the window if it was not opened using window.open or is a top-level window (or tab) with at one history entry. That is what the documentation of window.close says.

It got in the way.

I was adding a page endpoint that I would link to. The link would open the page in a new tab with target="_blank". And it would call window.print and window.close back to back.

Adding Anchor Links Next to Headings in Hugo

m@hjr265.me (Mahmud Ridwan) — Fri, 03 Nov 2023 10:00:00 +0600

I like that the Markdown renderer in Hugo automatically adds an id attribute to the headings in the content.

This allows you to link to a specific section in a long article.

But, I wanted to make it easy for people to get that link.

Hugo doesn’t do that by default, but makes it very easy to do with Markdown render hooks.

By using the following as the render hook for headings, I am able to show a small link icon next to the headings in my blog posts:

Setting Up Prometheus DNS-SRV Discovery with Terraform and DNSimple

m@hjr265.me (Mahmud Ridwan) — Thu, 02 Nov 2023 10:00:00 +0600

If you are using Prometheus to collect metrics from your server, and you don’t have a static set of servers, then you should set up automated discovery.

There are many ways you can set up automated discovery in Prometheus. However, one of my preferred vendor-agnostic ways of doing this is to use DNS-SRV records.

How does it work?

Let’s say you are using Terraform to manage your infrastructure.

You will be creating a DNS-SRV record for each of your servers. As you create or destroy servers, these records will be created and destroyed.

Waiting for an HTTP Service in GitLab CI/CD

m@hjr265.me (Mahmud Ridwan) — Wed, 01 Nov 2023 10:00:00 +0600

Last weekend, I was setting up a Cypress test pipeline in GitLab for Toph for the 5th time.

I have no idea why this pipeline keeps breaking over time. It’s like bread left in the open. Cypress is such a fantastic end-to-end testing tool. But it seems to need a lot of extra love.

Something that I needed to do was, in the CI/CD script, wait for Toph to start handling HTTP requests before starting Cypress.

SOCKS Proxy Over SSH

m@hjr265.me (Mahmud Ridwan) — Tue, 31 Oct 2023 13:00:00 +0600

To test some of Toph’s IP-based access control features, I needed to access it from a few different IP addresses than mine.

I thought I finally needed to get one of those VPN subscriptions YouTube content creators keep rambling about.

Fortunately, I remembered an easier way to do this.

You see, it is possible to run a SOCKS proxy that tunnels your connection over SSH. And it is built right into the ssh command:

Are There Three Types of #100DaysToOffload Challengers?

m@hjr265.me (Mahmud Ridwan) — Tue, 31 Oct 2023 10:00:00 +0600

A couple of weeks ago, I wrote my second #100DaysToOffload milestone blog post.

I mentioned how I feel like a remnant characteristic of my days in the university has played a role in taking this challenge. I have been writing more frequently as I am nearing the end of the challenge.

It got me wondering: are there three types of #100DaysToOffload challengers?

I took a quick look at some of the recent entries in the hall of fame and analyzed how the publication dates of the blog posts were spread out over a year of the challenge by these other challengers.

Uploading Files Over SSH in Go

m@hjr265.me (Mahmud Ridwan) — Sun, 29 Oct 2023 14:00:00 +0600

If you access servers remotely over SSH connections, you are bound to have come across scp. It is what you use to upload files to these remote servers.

If you want to programmatically upload files like scp over an SSH connection to a remote server using Go, then you can use an ssh.Client:

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// Error handling omitted for brevity.

func uploadFile(sshClient *ssh.Client, filename string, mode os.FileMode, size int64, r io.Reader) {
 // Set up a new SSH session.
 sess, _ := sshClient.NewSession()
 defer sess.Close()

 // Write the file's metadata and contents to the stdin pipe.
 w, _ := sess.StdinPipe()
 go func() {
 defer w.Close()
 // Write "C{mode} {size} {filename}\n"
 fmt.Fprintf(w, "C%#o %d %s\n", mode, size, path.Base(filename))
 // Write the file's contents.
 io.Copy(w, r)
 // End with a null byte.
 fmt.Fprint(w, "\x00")
 }()

 sess.Stdout = os.Stdout
 sess.Stderr = os.Stderr
 // Run `scp -t {filename}` on the server-side.
 sess.Run(fmt.Sprintf("scp -t %s", filename))
}

You can use this function like so:

Steam Link Black Screen on a Retro Pie Raspberry Pi 4

m@hjr265.me (Mahmud Ridwan) — Fri, 27 Oct 2023 08:30:00 +0600

Last night, I encountered a strange issue setting up Steam Link on a Raspberry Pi running Retro Pie.

Here is my attempt at a proper description of what I was seeing.

After installing Steam Link using Retro Pie’s package manager and rebooting the Raspberry Pi, I could see “Ports” show up on the Emulation Station. Inside was “Steam Link”.

I could start Steam Link just fine, have it test my network, and then pair it with Steam running on my gaming virtual machine.

Synchronization Constructs in the Go Standard Library

m@hjr265.me (Mahmud Ridwan) — Thu, 26 Oct 2023 15:30:00 +0600

Go provides sync.Mutex as its implementation of a mutual exclusion lock. However, it is not the only synchronization construct that is a part of the standard library.

This blog post will look at four synchronization constructs that we can use instead of a sync.Mutex.

Counter

You may often see code using a sync.Mutex to synchronize access to a counter variable from multiple goroutines.

Like this:

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var (
 n int
 m sync.Mutex
)
for i := 0; i < 7; i++ {
 go func() {
 m.Lock()
 defer m.Unlock()
 n++
 }()
}

// Elsewhere
m.Lock()
fmt.Println(n)
m.Unlock()

Instead of this, you can use an atomic.Int32 or atomic.Int64:

Powering on a Desktop Computer Remotely With a Raspberry Pi

m@hjr265.me (Mahmud Ridwan) — Wed, 25 Oct 2023 20:00:00 +0600

I access my primary computer remotely for various reasons.

Take playing video games using Steam Remote Play, for example. I have a Windows virtual machine with a GPU passed through. With Steam running on it, I can connect from my phone, my laptop, or any device with the Steam Link app and play remotely. For games that are not on Steam, I can use Moonlight.

But imagine the frustration when the computer is not powered on, and I am not at home. Only a fellow video gamer may understand it.

Serving hjr265.me From an S3-like Bucket Using a Caddy Module

m@hjr265.me (Mahmud Ridwan) — Tue, 24 Oct 2023 15:00:00 +0600

I serve hjr265.me from an S3-like bucket hosted on Linode Object Storage. I have a Caddy instance that serves some of my Hugo-built websites, including this one.

I use Hugo’s deployment function and s3cmd to deploy these websites.

Why Both?

Hugo’s deployment function uses the blob package from the Go Cloud Development Kit. This package comes with a limitation by design. It cannot set S3 access control lists (ACLs) for the uploaded objects. So neither can Hugo.

Switch Monitor Input from Linux Command Line

m@hjr265.me (Mahmud Ridwan) — Tue, 24 Oct 2023 10:00:00 +0600

For the longest time, I have looked at computer monitors as these dumb devices. All they do is turn video signals into colours on the screen.

I was out of touch with the progress.

Most modern computer monitors come with what is known as DDC/CI. It may be disabled by default, so you need to enable it using the monitor’s on-screen display (OSD) settings.

Then, use a tool like ddcutil to switch the current input of the monitor.

Making a Real-time "Last N Days" Leaderboard with MongoDB Aggregation Framework

m@hjr265.me (Mahmud Ridwan) — Sun, 22 Oct 2023 18:45:00 +0600

On Toph, there is a leaderboard of top solvers. Without any filters, this leaderboard shows the list of programmers who solved the most programming problems in the last seven days. Toph updates the leaderboard in real-time.

There are a few ways to build a leaderboard like this one.

The Naive Way

The easy way is to run a daily or hourly cron that aggregates all the solutions submitted over the last seven days and regenerates the leaderboard. However, the leaderboard will be far from real-time with this approach.

Windows Is Weird

m@hjr265.me (Mahmud Ridwan) — Fri, 20 Oct 2023 12:30:00 +0600

I know we could list a thousand reasons why Windows is weird. But this particular reason is my favourite.

Here are the N steps to my favourite Windows 10 weirdness:

Copy the URL to this blog post.

https://hjr265.me/blog/windows-is-weird/

Paste the URL in a Notepad window. You see the entire URL to this blog post. Good.
Open File Explorer. Right-click on an empty area in the window. Click on New › Folder. Paste the URL as the name of the folder.

Show a Log Throbber in Terminal with Go

m@hjr265.me (Mahmud Ridwan) — Thu, 19 Oct 2023 10:00:00 +0600

Show a Log Throbber in the Terminal with Go

A long-running program made to run in a terminal window should indicate what it is doing. Judicious logging is the first step.

While developing Printd for Toph, we needed a way to indicate the program status without outputting loglines repeatedly.

Printd, a print server daemon, waits for print requests from Toph and prints out the contents of the request to a connected printer. Until these requests arrive, Printd is mostly sitting idle.

Not a "High-rated" Person

m@hjr265.me (Mahmud Ridwan) — Wed, 18 Oct 2023 10:00:00 +0600

I came across a post in a competitive programming community. The post read:

Always felt like [competitive programming] is no different from any other sport. Trying to get to the top in any sport requires the ability to keep being persistent in your work irrespective of the situation and what people say. […] I personally have trained myself so far so that I do the work irrespective of any situation and no matter what emotions I go through, But hasn’t yet completely grasped it. Like how to build that mentality very strongly that how I feel has no impact on my work. Would be helpful if some very high rated people would share their opinions.

Gnome Not Reporting Bluetooth Earbuds Battery? Enable the D-Bus Interface

m@hjr265.me (Mahmud Ridwan) — Tue, 17 Oct 2023 10:00:00 +0600

I use one of these true wireless Edifier earbuds.

I noticed how Android reports the battery level of these earphones. But Gnome doesn’t.

Turns out, you need to enable the experimental D-Bus interface in the Bluetooth daemon on Linux for Gnome to know the battery level of the connected wireless earbuds.

On Arch Linux (which I use, btw), I had to modify /etc/bluetooth/main.conf and set:

Experimental = true

You will probably find a # Experimental = false line in that file that you can uncomment and change from false to true.

#100DaysToOffload Milestone: The 67th Blog Post

m@hjr265.me (Mahmud Ridwan) — Mon, 16 Oct 2023 10:00:00 +0600

It is my second milestone blog post of the #100DaysToOffload challenge. I posted my first milestone blog post on September 3, 2023.

I will keep this one short.

But I will say that I have posted as many #100DaysToOffload blog posts in the last 43 days as I have since I started the challenge.

It is probably a remnant characteristic of my days in the university. Something I should work on changing. Maybe I will get to this after I finish this challenge.

10 Forms of Bash Shell Parameter Expansion

m@hjr265.me (Mahmud Ridwan) — Sun, 15 Oct 2023 10:00:00 +0600

If I look at my search history with the word “bash” in it, the most frequently searched phrases turn out to be like “trim suffix bash” and “set bash variable if empty”.

It seems I write Bash scripts frequently enough to need these, but not frequently enough to remember these simple Bash shell parameter expansion forms.

In this blog post I am going to keep a list of 10 forms of Bash shell parameter expansion, that I hope will save me a visit to google.com.

Parsing Social Media URLs in Go With Slinky

m@hjr265.me (Mahmud Ridwan) — Sat, 14 Oct 2023 10:20:00 +0600

Toph now allows programmers to show up to 5 social media URLs on their profile pages.

Instead of showing the entire URL, I wanted to show the important bits from the URL.

Screenshot of a profile panel from Toph

To do that, I had to parse the social media URLs and extract information like the username or profile ID (when it is a GitHub, Twitter, LinkedIn, Facebook, etc. profile URL) or the instance of Mastodon.

Fixing Creality CR-10 Smart Touch Screen Orientation Issue

m@hjr265.me (Mahmud Ridwan) — Fri, 13 Oct 2023 10:00:00 +0600

The Creality CR-10 Smart is a very sensitive 3D printer, especially when updating firmware.

Are you using an SD card that is too small? The printer won’t update. Too large? Again, the printer won’t update.

You formatted it to FAT32 but used an allocation size that isn’t exactly 4096 KB. Tough luck: the printer won’t update.

You successfully updated the firmware to CR-10 Smart Marlin2.0.6SWV1.0.14HWCRC2405V1.2.zip? Well, now your touch screen is going to behave weirdly.

Bash Script to Auto-archive Downloads by Date

m@hjr265.me (Mahmud Ridwan) — Wed, 11 Oct 2023 10:00:00 +0600

Finding the files you are looking for without combing through hundreds of directories is a true time-saver and an easy productivity move.

I try to keep my files and directories in order, named and organized neatly. I don’t have stale files at the base of my home directory. I have separate directories for my projects, my company stuff, and the work I do for my clients.

But my ~/Downloads directory is always a colossal mess.

Stardew Valley and Eric Barone

m@hjr265.me (Mahmud Ridwan) — Tue, 10 Oct 2023 10:00:00 +0600

It is no secret that I play video games. Over the years, I, no doubt, have learned a lot from video games.

But one particular video game and its developer stand out the most.

Stardew Valley

A friend of mine at school introduced me to Harvest Moon. I had tried it before, but he introduced me to the mechanics and quirks of Harvest Moon, which got me hooked on the genre.

Building a Blog With Hugo

m@hjr265.me (Mahmud Ridwan) — Mon, 09 Oct 2023 10:00:00 +0600

A few weeks ago, I came across a blog post on my RSS reader: Building a blog in Django.

This simple tutorial by Simon Willison was an enjoyable read.

I understand the topic is not novel, but I liked how it reminds you of the simple features that enhance the implementation of a blog.

Quoting from the blog post by Simon Willison:

Here are the features I consider to be essential for a blog in 2023 (though they haven’t changed much in over a decade):

Setup HTTP3 with NGINX Mainline

m@hjr265.me (Mahmud Ridwan) — Sun, 08 Oct 2023 10:00:00 +0600

HTTP3 is here. Well, almost.

If you are using NGINX, you can update to the mainline version and start using HTTP3 today experimentally.

Installing NGINX Mainline

As of writing this blog post, NGINX v1.24 is the latest stable version. But, HTTP3 is available in v1.25.

On Ubuntu/Debian-esque servers, the easiest way to install the mainline NGINX version is to use NGINX’s official repository.

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apt install curl gnupg2 ca-certificates lsb-release debian-archive-keyring

# Import the official NGINX signing key.
curl https://nginx.org/keys/nginx_signing.key | gpg --dearmor \
 | tee /usr/share/keyrings/nginx-archive-keyring.gpg >/dev/null

# Add the APT repository.
echo "deb [signed-by=/usr/share/keyrings/nginx-archive-keyring.gpg] \
http://nginx.org/packages/mainline/debian `lsb_release -cs` nginx" \
 | tee /etc/apt/sources.list.d/nginx.list

# Install NGINX.
apt update
apt install nginx=1.25.*

nginx -v # Verify installation.

Alternatively, you can also do this in Docker.

Prevent Git Commits with Unformatted Go Code

m@hjr265.me (Mahmud Ridwan) — Sat, 07 Oct 2023 10:10:00 +0600

Git has this great feature that I think is well-known but under-used. I am talking about Git hooks.

With Git hooks, you can run scripts during different Git actions.

Like this one:

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#!/bin/sh

GOFILES=`git diff --name-only --cached | grep -e '.go$' | grep -ve 'vendor/'`
UNFMTFILES=()
for f in $GOFILES; do
 if [ -n "`gofmt -l -s ./"$f"`" ]; then
 UNFMTFILES+=("$f")
 fi
done

if [ ${#UNFMTFILES[@]} -gt 0 ]; then
 echo You have staged unformatted Go files. Please run \`go fmt\` first.
 for f in ${UNFMTFILES[@]}; do
 echo " $f"
 done
 exit 1
fi

This script will take a list of all the staged Go files. It will then run gofmt to determine if these Go files are not formatted.

Mattermost (or Slack) Message on SSH Login

m@hjr265.me (Mahmud Ridwan) — Thu, 05 Oct 2023 15:05:00 +0600

You have a server that you access over SSH. You have hardened it following the necessary best practices.

Now you can do one small thing for a little additional peace of mind: Set up Linux Pluggable Authentication Modules (PAM) to send a message to Mattermost (or Slack) on every successful SSH login.

Here is how you can do it:

Add a script to /usr/local/bin/ to send the notification message. Name it sshnotify.sh. Make it executable.

Allow External Keyboard to Wake Laptop

m@hjr265.me (Mahmud Ridwan) — Wed, 04 Oct 2023 13:15:00 +0600

My setup at my workspace isn’t much: a display and a few peripherals connected to a USB-C hub. This way, I can come in, plug in the hub to my laptop, and start working.

But if my laptop goes to sleep, I can wake it up only by pressing a key on the internal keyboard or the trackpad. Since I keep the lid of my laptop closed, I have to take it out of the stand first, then open the lid (which causes the laptop to wake up anyway).

Over-engineered URLs vs. A Little Script

m@hjr265.me (Mahmud Ridwan) — Wed, 04 Oct 2023 08:15:00 +0600

One of the local courier services where I live will send you this helpful notification SMS with a tracking URL whenever they pick up a parcel for you. It is useful. At least compared to the hundreds of spam text messages we get here daily.

It reads: [{Courier}] We have collected your parcel {ID} from {Vendor}. Track {MaskedURL}.

The tracking URL is masked, much like a shortened URL, but not exactly short. The URL will redirect you to the real tracking URL only if you are not accessing it from a mobile device.

Adding Icons for Go-built Windows Executable

m@hjr265.me (Mahmud Ridwan) — Sat, 30 Sep 2023 19:55:00 +0600

I have been using Windows for video games only for several years now. But that changed a little as I started working on Printd, Toph’s print server daemon.

An executable file (.exe) on Windows can provide its icons. If you build a Go program for Windows you get the generic executable icon, which is fine. But sometimes fine isn’t enough.

Detect If Go Built Windows Executable Is Run From Command Prompt or File Explorer

m@hjr265.me (Mahmud Ridwan) — Sat, 30 Sep 2023 11:00:00 +0600

In Windows, unlike the Unix-like POSIX-compatible operating systems, there is this notion of an application subsystem: console vs. windows.

If you build a Go program for Windows, it will, by default, use the console subsystem. When you start this program from File Explorer (e.g. by double-clicking its icon), Windows will show a console (like the Command Prompt window) and run the program inside the console.

When running a console subsystem program that finishes quickly, you may notice the console window appears and disappears quickly. You may not even see it flash.

Go Tidbit: Retain Cache to Speed up Go Builds in Docker

m@hjr265.me (Mahmud Ridwan) — Fri, 29 Sep 2023 20:20:00 +0600

If you are building Go binaries inside a Docker container, you can speed up the builds by retaining the cache that go build creates between builds.

This tidbit is especially effective for large projects with several packages.

Let’s take one of my Go projects as an example.

Toph Platform, the Go project that powers the web application at toph.co has 55 packages inside the repository. If I include dependencies (first and third-party), the total number of packages comes to 813.

Go Tidbit: Listing All Time Zones in Go

m@hjr265.me (Mahmud Ridwan) — Sun, 24 Sep 2023 19:45:00 +0600

I wanted to list all the time zones in Go.

The standard library in Go comes with the time package. It also comes with the time/tzdata package.

The standard time package in Go is very well-thought-out. It makes date-time manipulation deceptively simple.

Yet, I could not find a way to list all the time zones.

Time Zone Database

The documentation for time.LoadLocation describes how Go uses four sources of time zone data:

Setup Dnsmasq and Systemd-resolved for *.local Hostnames

m@hjr265.me (Mahmud Ridwan) — Sat, 23 Sep 2023 17:30:00 +0600

I have lines like these in my /etc/hosts file:

127.0.0.1 toph.local
127.0.0.1 drafts.toph.local
127.0.0.1 quiz.toph.local

I can run development servers locally and access them over .local hostnames (e.g. toph.local) instead of the loopback IP addresses (e.g. 127.0.0.1).

It works fine. But every time I start working on a new project, I needed to add a new line to the /etc/hosts file. It didn’t sit right with me.

I should be able to point all *.local hostnames to a loopback IP address without having to enter each possible hostname. Right?

Making an Auto Scroll Bookmarklet

m@hjr265.me (Mahmud Ridwan) — Fri, 22 Sep 2023 18:05:00 +0600

We have extensions and addons that add features and customizations to our web browsers. But it wasn’t always the case.

During the the early 2000s (and even later) there were bookmarklets. Bookmarklets are short JavaScript scripts stored as bookmarks in your web browser.

These were popular during the 2000s. However they started to decline in popularity when browser extensions became easier to build and more and more websites started to implement Content Security Policy (CSP).

HTML Markup (and Hugo Shortcode) for the Modern Web

m@hjr265.me (Mahmud Ridwan) — Fri, 22 Sep 2023 10:30:00 +0600

I am by no means an expert in HTML and CSS. But I have been tweaking and tuning a few of my Hugo-powered websites, including this one. And, I had the opportunity to explore a few of the modern HTML and CSS features.

Starting last month I made it a point to use more images in my blog posts.

And, I am glad I did. When I wrote the blog post on hiding files in ZIP archives, I enjoyed preparing the ZIP format illustrations.

Go Tidbit: Detect When the Terminal Is Resized

m@hjr265.me (Mahmud Ridwan) — Wed, 20 Sep 2023 21:00:00 +0600

I have been meaning to do a few short-form blog posts lately. This blog post is going to be one of them.

In Go, on Linux, if you want to know when the terminal window is resized, you can listen for the SIGWINCH signal using the signal.Notify (or the signal.NotifyContext) function.

The code will look something like this:

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ch := make(chan os.Signal)
signal.Notify(ch, syscall.SIGWINCH)
for range ch {
 // The terminal has been resized.
}

For a bit more complete example, you can try out this Go code:

Go Tidbit: Putting The Terminal Into Raw Mode

m@hjr265.me (Mahmud Ridwan) — Wed, 20 Sep 2023 00:15:00 +0600

I learned something new today. It helped solve a long-standing bug in Bullet.

Bullet is an application deployment tool that I wrote several years ago. It is a simple tool that SSHs into a server and uses Docker to run applications.

I use it in production for some of my projects.

About the Bug

Bullet can SSH into a remote server, spin up a one-off container and attach the terminal to it. You could run commands in that container as if you were SSH’ed directly into that environment.

Go Tidbit: Waiting on Go Routines

m@hjr265.me (Mahmud Ridwan) — Sun, 17 Sep 2023 21:15:00 +0600

Concurrency is one of the central features of Go. And, to build concurrent programs in Go, you need goroutines.

A goroutine is like a thread, but lighter. Much lighter. And, like any other built-in feature of Go, using it is dead simple:

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package main

func main() {
 go func() {
 println("Hello World") // Print "Hello World" from a different goroutine.
 }()
}

Wait. That didn’t print anything.

Hiding Files in ZIP Archives

m@hjr265.me (Mahmud Ridwan) — Sat, 16 Sep 2023 10:15:00 +0600

I remember seeing a tool many years ago that could hide other files in BMP image files. I was a bit too young to understand how it worked, but I think I understand the trick now:

Understand the structure of the file type at the byte level.
Find a spot that can hold an arbitrary length of data.
Sneak in whatever you want in there.

As a proof of concept, I used Go to make Sneak - a program to add or extract a hidden file in a ZIP archive.

Make a Part of Form Non-interactable With CSS

m@hjr265.me (Mahmud Ridwan) — Fri, 15 Sep 2023 17:30:00 +0600

I have an HTML form. I want to make part of it non-interactable depending on certain conditions. I don’t want to remove that part entirely.

There are so many reasons why you may want to do this.

Screenshot of Contest Branding Settings Form from Toph

In this screenshot, the form allows advanced features to pay customers only. Making that part non-interactable, instead of hiding it, works as a teaser of what the paid tiers offer.

5 Upkeep Tips for Arch Linux

m@hjr265.me (Mahmud Ridwan) — Wed, 13 Sep 2023 00:16:00 +0600

Yes, I am one of those guys: “I use Arch btw”.

After distro-hopping for almost my entire time at the university, I found Arch Linux. I did momentarily switch to a MacBook after that, but I don’t think I have tried any other Linux distribution for over a decade.

Arch Linux doesn’t do everything the way I like on a Linux device. But it doesn’t make me feel like switching to another distribution.

Setup Multiple Passphrases for a LUKS Device

m@hjr265.me (Mahmud Ridwan) — Wed, 13 Sep 2023 00:10:00 +0600

Let’s say you have a computer at home shared by multiple people. And, you want to encrypt your hard drive with LUKS but not have to use the same passphrase.

You can do that. LUKS has 8 key slots (LUKS1 does, LUKS2 can support more).

When you set up a LUKS encrypted device you are configuring the first key slot only.

But by running the following command you can set up an additional passphrase:

Building Multi-platform Docker Image for Go Applications

m@hjr265.me (Mahmud Ridwan) — Sun, 10 Sep 2023 21:20:00 +0600

I began the weekend writing a silly program: MGHSIAC. It’s the elegant abbreviation of “My GitHub Status Is A Clock”. It turns my GitHub status into a working clock. You can read more about it here.

But as silly as it is, I am now committed to keep it running.

I have an always-on Raspberry Pi with Portainer running on it already. If I could make a Docker image and host it on Docker Hub, I could easily pull it to that Raspberry Pi and have it continuously update my GitHub status with clock emojis and messages.

Private Cloud on a Raspberry Pi: Hardware

m@hjr265.me (Mahmud Ridwan) — Sat, 09 Sep 2023 18:00:00 +0600

I don’t think I take privacy as seriously as people should. It is hard.

Where I live, banks ask you to send documents over WhatsApp. I don’t use WhatsApp. When I ask for an email address instead, bank employees often take a few seconds before responding.

But I also believe in taking baby steps.

For the last few years, I have been storing bits of my life on a Raspberry Pi instead of the Internet. Bits include contacts, to-do lists, passwords, photos and videos, and more.

My GitHub Status Is A Clock

m@hjr265.me (Mahmud Ridwan) — Sat, 09 Sep 2023 00:30:00 +0600

On GitHub, you can set an emoji and a short message as your status. I don’t browse GitHub much. But through what little I do, I see so many profiles with “:dart: Focusing”.

Why not make it a clock? An almost functional clock.

That’s exactly what I did.: github.com/hjr265

Screenshot of my GitHub profile

I wrote a Go program that I can leave running. The program updates my GitHub status with one of the clock emojis (one that is close to the current time) and a message saying something like “Twelve o’clock” or “Half past twelve”.

Pregenerate Colorful Letter Avatars With Go

m@hjr265.me (Mahmud Ridwan) — Fri, 08 Sep 2023 16:30:00 +0600

Avatars (also known as profile images) are a great way to represent users in web applications (especially in the ones with social or collaborative features). It’s like icons, but for human beings.

But as your application grows, you start to realize that not everyone is quick to upload an avatar for their account.

If your application uses one of those silhouette images as a fallback avatar, then soon you will have more “John Doe” avatars than personalized ones. Not cool to look at when there are 10 avatars side-by-side and they are all this grey human silhouette.

Making a Gnome Background Slide Show

m@hjr265.me (Mahmud Ridwan) — Thu, 07 Sep 2023 11:50:00 +0600

“Background Slide Show”. That is what Gnome uses in code to refer to its time-based dynamic backgrounds feature.

Instead of having a static background, a Gnome Background Slide Show allows you to have a set of images that Gnome selects from based on the current time of the day. You can also configure the dynamic background to use transitions when changing from one picture to the next.

There are tools that you can install to build dynamic backgrounds. But I wanted to read some documentation and figure out how it works.

Client-side Search in Hugo with Fuse.js

m@hjr265.me (Mahmud Ridwan) — Wed, 06 Sep 2023 19:20:00 +0600

Toph Help is built with Hugo - a static site generator.

As you would expect with static sites, the pages are all generated ahead of time and hosted as plain HTML. You get all the benefits of static websites, but what about search?

Client-side search is one way to work around this limitation of static websites.

You build an array of objects describing all your pages on your website. You serve it to the client as JSON. You use the JSON with client-side JavaScript to provide fast search functionality.

Shell Script for the #100DaysToOffload Challenge

m@hjr265.me (Mahmud Ridwan) — Wed, 06 Sep 2023 10:30:00 +0600

I am getting quite close to my 1-year mark since I started the #100DaysToOffload challenge. Some quick mafs tell me that I can’t skip that many days if I want to make it to 100 blog posts by the end of the 365 days.

I wrote a script that takes the date when I made my first #100DaysToOffload blog post and the number of blog posts I have written through for challenge so far. The script then calculates some numbers to… motivate.

#100DaysToOffload Milestone: The 34th Blog Post

m@hjr265.me (Mahmud Ridwan) — Sun, 03 Sep 2023 12:30:00 +0600

What is #100DaysToOffload?

#100DaysToOffload is an Internet challenge created by Kev Quirk.

I don’t quite recall how I came across this challenge, probably through a front-page entry on Hacker News. But, I am glad I did.

The goal of this challenge is simple: To encourage you to write.

The whole point of #100DaysToOffload is to challenge you to publish 100 posts on your personal blog in a year. […]

Configuring Docker Health Check for Go Web Applications

m@hjr265.me (Mahmud Ridwan) — Sat, 02 Sep 2023 12:45:00 +0600

Docker has been providing a health check mechanism for quite some time. It is useful in identifying issues with programs that can fail in ways other than just outright crashing.

And it is easy to set up.

Docker health checks work periodically running a program within the container and observing its exit status. If it exits with a 0, the container is considered healthy. If it exits with a 1, the container is considered to be unhealthy.

Certbot-Name.com DNS Challenge Hooks

m@hjr265.me (Mahmud Ridwan) — Fri, 01 Sep 2023 17:00:00 +0600

With Certbot, for SSL certificates, I tend to use its DNS challenge over the HTTP challenge method. I find it a lot easier to automate. And, I can keep the certificate renewal details and mechanisms off the balancer or application servers.

But I also have domains that are on Name.com. And, for some of them, I have their DNS records in the same place.

How do you then use Certbot’s DNS challenge method with Name.com domains?

Schedule MongoDB Backups with GitLab CI/CD

m@hjr265.me (Mahmud Ridwan) — Wed, 30 Aug 2023 15:00:00 +0600

GitLab CI/CD let’s you schedule pipelines. And, in a way, I find it such a convenient way to manage my Internet crons.

One use of GitLab CI/CD schedules that I make is to backup MongoDB data. The pipeline, when run, SSHs into a server holding the MongoDB instance, runs mongodump and pipes it straight to s3cmd that then stores the dumped archived to an S3-esque bucket.

Here’s what the pipeline looks like in .gitlab-ci.yaml:

Spam Story 01: A Not-Quite-Ethical Hacker

m@hjr265.me (Mahmud Ridwan) — Tue, 29 Aug 2023 10:20:00 +0600

On April 3, 2023, I received an email from a “security researcher”. The “security researcher” and his/her “expert team” scanned one of my sites and found a “critical urgent” vulnerability.

The web application in question links to a subdomain under the same domain from the footer without the rel="noreferer noopener" attribute.

Some will say that a subdomain is not an internal link and it must have that attribute. Fine.

Makefile Recipe: Build with Docker and Export To A Gzipped Tarball

m@hjr265.me (Mahmud Ridwan) — Mon, 28 Aug 2023 17:30:00 +0600

I have been writing a lot of Makefiles lately. I find them simple and easy to like. And, as with all old-school things, I am starting to overlook its quirks.

I needed to write a Makefile that lets me build something with Docker and then export the entire contents of the image to a gzipped tarball.

The first part is easy:

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.PHONY: build
build:
 (cd $(APP); docker build -t thing-$(APP):latest .)

When run as make build APP=something, it will build the Dockerfile within the something/ directory.

Presence Tracking with Redis

m@hjr265.me (Mahmud Ridwan) — Sun, 16 Jul 2023 18:30:00 +0600

Let’s say you are building a chat application. You have everything chalked out. The only thing left is that pesky green-yellow-grey indicator next to everyone’s avatar.

With Redis, there is an easy way to track and display the presence of your users. All you need is a Redis sorted set.

A Redis sorted set is a collection of unique strings (members) ordered by an associated score. …

Track Last Seen with ZADD

Using ZADD you can store your user’s identifier as a member in a sorted set and the time the user was “last seen” as its score:

Organizing Libvirt Hooks for Qemu

m@hjr265.me (Mahmud Ridwan) — Sun, 16 Jul 2023 16:30:00 +0600

Something I have been meaning to write about for a while is my KVM/VFIO-based gaming setup. Yes, I run Linux. And I run Windows, on Linux, in a virtual machine (VM). And it works! I game on it almost every day.

But the longer post has to wait for another day.

Today I am just sharing the short script that lets me keep my Libvirt hooks for Qemu a tad more organized:

Hugo Footnote for the 100 Days to Offload Challenge

m@hjr265.me (Mahmud Ridwan) — Sat, 01 Jul 2023 19:50:00 +0600

Yesterday I posted my 25th blog post for the #100DaysToOffload. That’s 25% of the challenge.

If it wasn’t clear by the post Showing GitHub Stars With Static Site Generator Hugo, I use Hugo for this site.

All this time, I was manually adding a footnote to each of the blog posts:

This post is {n}th of my #100DaysToOffload challenge. Want to get involved? Find out more at 100daystooffload.com.

Figuring out what {n} is for each blog post wasn’t fun.

Simple Fixed-window Rate Limiter With Redis

m@hjr265.me (Mahmud Ridwan) — Sat, 01 Jul 2023 19:50:00 +0600

A while ago I needed a very quick rate limiter implementation. The application I was working on was already using Redis.

Fixed-window rate limiting: This is a straightforward algorithm that counts the number of requests received within a fixed time window, such as one minute. Once the maximum number of requests is reached, additional requests are rejected until the next window begins. …

With a small Redis script, I was able to implement a fixed-window rate limiter:

Makeshift CDN for Linode Object Storage with NGINX for Discourse

m@hjr265.me (Mahmud Ridwan) — Mon, 26 Jun 2023 09:15:00 +0600

If you use S3-like object storage for Discourse uploads, you will quickly realize that Discourse strongly recommends a CDN.

Not using a CDN (or entering the bucket URL as the CDN URL) is likely to cause problems and is not supported. […]

If you were to use Amazon S3, their Cloudfront service would be the easy solution. But not all cloud providers (e.g. Linode referral) providing S3-like services has CDN offerings. For such cases NGINX with reverse proxy caching can work well as a makeshift CDN.

Memory Game in Less Than 100 Lines of JavaScript

m@hjr265.me (Mahmud Ridwan) — Sat, 24 Jun 2023 13:06:00 +0600

With Toph, for me, the line between work and fun blurs.

I wanted to add a small in-browser game to Toph that would allow contest participants to pass the time while waiting for the contest to begin.

The thing about 100 lines of JavaScript is arbitrary. I wanted to make the most out of modern CSS features and use JavaScript only where necessary.

Without further ado, here’s the game:

You can find the source code for this game on GitHub. It is also available on NPM.

Go Tidbit: Update Checker with GitHub Releases

m@hjr265.me (Mahmud Ridwan) — Sat, 24 Jun 2023 12:11:00 +0600

After building Printd, Toph’s print daemon, it became necessary to ensure that contest organizers were using the latest version of the software. Since Printd is open-source we host both the code and the release artifacts on GitHub.

The following function uses the Go client library for GitHub to check the latest release and compare the tag with the current version.

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package main

import (
	"context"
	"log"
	"time"

	"github.com/google/go-github/v53/github"
	"golang.org/x/mod/semver"
)

var (
	buildTag = "v0.3.0"

	repoOwner = "FurqanSoftware"
	repoName = "toph-printd"
)

func checkUpdate(ctx context.Context) error {
	// Give your program at most 5 seconds to check for updates.
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	// Check the latest release on GitHub.
	client := github.NewClient(nil)
	rel, _, err := client.Repositories.GetLatestRelease(ctx, repoOwner, repoName)
	if err != nil || rel == nil || rel.TagName == nil {
		return err
	}

	// Check if the latest release is newer than the current version.
	if semver.Compare(*rel.TagName, buildTag) > 0 {
		log.Printf("Update available (%s)", *rel.TagName)
	}

	return nil
}

Since the API is accessible publicly you do not need to authenticate the GitHub API requests.

Generate SSH Known Hosts in Terraform

m@hjr265.me (Mahmud Ridwan) — Fri, 24 Mar 2023 10:30:00 +0600

I manage Toph’s infrastructure with Terraform. The setup is as multi-cloud as it gets. Beyond Terraform, I have several Ansible Playbooks for configuring and upkeeping the infrastructure.

Something that I wanted to do with Terraform was to generate an SSH known_hosts file ahead of time as any changes are applied to the infrastructure. There isn’t a straightforward way to do that in Terraform. But the workaround is simple too.

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locals {
 ssh_hosts = merge(
 [for i, v in vultr_instance.servers : { host = v.main_ip, port = 22 }],
 [for i, v in linode_instance.servers : { host = v.ip_address, port = 22 }],
 # ...
 )
}

resource "null_resource" "known_hosts" {
 provisioner "local-exec" {
 command = <<EOT
 rm -f known_hosts;
%{ for i, host in local.ssh_hosts }
 ssh-keyscan -p ${host.port} ${host.host} >> known_hosts;
%{ endfor ~}
EOT
 interpreter = ["/bin/bash", "-c"]
 }
}

All you need to do is put all your SSH hostnames/addresses and ports in a local variable. And, then use a local-exec provisioner in a null_resource to run ssh-keyscan for each host, appending the output to a “known_hosts” file.

Randomised Suffix in Terraform Resource Names

m@hjr265.me (Mahmud Ridwan) — Mon, 13 Mar 2023 20:30:00 +0600

I didn’t like how I named cloud resources for Toph. The resource names had sequential suffixes at the end.

Let’s take Toph’s storage servers, for example, where MongoDB replicas are running. On Linode, while they were there, I had named the three storage servers as toph-storage-sgp-1, toph-storage-sgp-2 and toph-storage-sgp-3.

But as I moved them over to Vultr (referral) last week, I realised that eliminating these sequential numbers could remove any notion of preference/precedence among these three servers.

Go Tidbit: Filtering Slices In-place

m@hjr265.me (Mahmud Ridwan) — Mon, 06 Mar 2023 20:15:00 +0600

At launch, Go did many things that felt out of place next to the other popular programming languages of the era. But now, those same language features feel so natural that I find it hard to think of a time without them.

One such feature is the slice type. In Go, a slice is a view of an array. And naturally, you can have multiple slices backed by the same array:

Making Ranked Leaderboards with MongoDB Aggregation Framework

m@hjr265.me (Mahmud Ridwan) — Sat, 11 Feb 2023 11:55:00 +0600

When I first added the leaderboard on Toph several years ago, I had to do most of the leaderboard-related things in application code. But then MongoDB introduced the $setWindowFields aggregation operator in MongoDB 5.0. And it simplified so much when it came to implementing ranked leaderboards.

One of the things that I had to do in the application code was to calculate the rank of the leaderboard entries.

In this tutorial, we will see how the same can be done using MongoDB’s aggregation pipelines.

Go Tidbit: Handling Signals, Exiting Gracefully

m@hjr265.me (Mahmud Ridwan) — Thu, 09 Feb 2023 20:25:00 +0600

Signals are standardized messages that an operating system can send your programs.

Take Ctrl+C for example. When running a program from the terminal and you hit Ctrl+C, you expect the program to end immediately.

How does that work, though? Ctrl+C is a shortcut for the POSIX signal SIGINT. By default, this signal causes your program to be terminated.

But this is one of those signals you can handle: You can intercept it and do whatever you please.

Go Tidbit: Setting Variables in Go During Build

m@hjr265.me (Mahmud Ridwan) — Tue, 07 Feb 2023 22:40:00 +0600

Last week I was working on a Go program. I wanted it to print the closest Git tag and build time to logs at startup.

I could write a small script that generates a Go file with these two variables set right before building the Go program.

But, Go makes it easier.

Ldflags

Say you have the following Go code:

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package main

var hello string

func main() {
 println(hello)
}

You can build it like so:

Go Tidbit: Ellipsize Strings Without Breaking Unicode

m@hjr265.me (Mahmud Ridwan) — Mon, 06 Feb 2023 21:00:00 +0600

Strings in Go support Unicode. If you come from a programming language like C, you may think of strings as an array of (byte-sized) characters.

In Go, you can convert a string to a byte slice, and access/manipulate each byte. But if you want to truncate or ellipsize the string to a specific length, you have to think of a string like a slice of runes.

Take this string for example: "বাংলাদেশ".

Go Tidbit: Peek a Snippet From io.Reader

m@hjr265.me (Mahmud Ridwan) — Sun, 05 Feb 2023 13:40:00 +0600

You have an io.Reader, and you want to extract a small snippet from the beginning of the io.Reader and then put it back.

Ideally, io.ReadSeeker would let you do that. But not all io.Readers can seek.

And, like toothpaste from its tube, you cannot put something back once you read it from an io.Reader. But you can do the next best thing:

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// PeekSnippet takes r and returns the first n bytes from it and another
// io.Reader with the entire data.
func PeekSnippet(r io.Reader, n int) ([]byte, io.Reader, error) {
	lr := io.LimitReader(r, n)
	b, err := io.ReadAll(lr) // Read first n bytes from r through lr.
	if err != nil {
		return nil, nil, err
	}
	r = io.MultiReader(bytes.NewReader(b), r) // Make a new reader combining the bytes just read and the remaining data in r.
	return b, r, nil
}

As you can see, you can use io.LimitReader to read the first n bytes. Then use io.MultiReader to combine those bytes with the remainder of data in r.

Go Tidbit: How Much Was Read From io.Reader?

m@hjr265.me (Mahmud Ridwan) — Sun, 05 Feb 2023 12:50:00 +0600

You have an io.Reader, and you are about to pass it to some utility that will read from it. But the utility won’t tell you how much it has read from the io.Reader.

How do you figure out how many bytes of data were in the io.Reader?

Like this snippet of Go+AWS code:

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func uploadToS3(r io.Reader) (int64, error) {
	_, err := s3manager.NewUploader(awsSess).Upload(&s3manager.UploadInput{
		Bucket: aws.String("some-bucket"),
		Key: aws.String(b.Path),
		Body: r,
	})
	// How many bytes were in r?
	return 0, err
}

You could implement a type that wraps the io.Reader and proxies all calls to Read while keeping track of the number of bytes read.

Using Caddy to Indicate GitLab Repository for Go Module Path with Different Domains

m@hjr265.me (Mahmud Ridwan) — Sat, 21 Jan 2023 11:05:00 +0600

The self-hosted GitLab at my company, Furqan Software, is home to all the company Go projects. The domain where Furqan Software’s GitLab is accessible is different from the domain in Go module paths. That means go get doesn’t work out of the box for our Go projects.

For example, let’s say you have a Go project with the module path go.example.com/tools/aglet. And the corresponding GitLab project is at https://gitlab.example.com/tools/aglet. If you run go get go.example.com/tools/aglet, you will see an error from go get about not finding the repository.

Private and Secure Multi-cloud Network with WireGuard

m@hjr265.me (Mahmud Ridwan) — Tue, 17 Jan 2023 13:05:00 +0600

Can you make a private and secure network between servers on multiple cloud providers?

Yes, with WireGuard, you can. The solution is fast and secure. It is easy to deploy/automate. And, best of all, it is cloud-agnostic.

For convenience, I have created a demo repository with Terraform and Ansible that you can clone and try. The demo uses Linode (referral) and Vultr (referral).

In this article, I will walk you through the inner workings of the demo and this solution.

Links for Social Network Share Dialogs

m@hjr265.me (Mahmud Ridwan) — Sat, 07 Jan 2023 11:20:00 +0600

You have a few options to add social network sharing buttons to your website or web app.

One, you can embed their JavaScript ~~operating systems~~ SDKs. If your site needs 21st-century Internet bloat, this is what you are looking for.

Two, you can use third-party share button JavaScript libraries. There are way too many of these out there. And they are just a “google” away. I will refrain from linking to any.

Embedding a JavaScript Library (KaTeX) in Go

m@hjr265.me (Mahmud Ridwan) — Sat, 24 Dec 2022 10:35:00 +0600

KaTeX is the fan-favourite way of doing math and equations on the web. The library is simple to use and easy to reason about. But it is JavaScript. How do you build a Go program that renders math and equations like KaTeX?

You embed KaTeX in your Go program.

Several Go packages allow you to run JavaScript from within Go. In this post, we will use github.com/lithdew/quickjs.

Let us first fetch the latest copy of katex.min.js from CDNJS. KaTeX uses the MIT license; make sure to include that in your project.

Block All But One Website With Windows Defender Firewall

m@hjr265.me (Mahmud Ridwan) — Sun, 11 Dec 2022 00:15:00 +0600

How do you block access to all websites except one on a Windows device?

On-site programming contest organizers need to ensure that the contestant workstations can access Toph but no other website.

Toph recommends restricting the Internet through router/firewall configuration; sometimes, it is not a solution that the contest organizer can choose. At one of the recent divisional programming contests in Bangladesh, the only option was to configure each contestant’s workstation to restrict the Internet.

Preparing Myself to Learn Programming

m@hjr265.me (Mahmud Ridwan) — Thu, 08 Dec 2022 14:50:00 +0600

My first exposure to any programming involved writing Batch scripts - think shell scripts for Windows.

The first time I used a computer was an IBM XT clone. It ran DOS.

I was 11 when I got my second computer, a nifty Windows 95 machine. I kept all of my games organized on that second computer. One day, I thought of making a number-based menu for my games using Batch scripts. That’s where it started.

Adding target="_blank" to User-Generated HTML Anchors in Go

m@hjr265.me (Mahmud Ridwan) — Tue, 06 Dec 2022 16:00:00 +0600

Working with user-generated content is always ~~a nightmare~~ interesting.

Let’s say you are building a blogging platform with Go. Your users write posts in Markdown that the platform then renders as HTML. And, you want to add target="_blank" and rel="noreferrer noopener" to all the external links. How do you do that?

Annotated Code

The steps are simple:

Parse the HTML with golang.org/x/net/html.
Walk the tree. The annotated code below implements a simple Walk function.
Update the nodes. Do this in the callback of the Walk function.
Render the modified HTML.

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package main

import (
	"bytes"
	"fmt"
	"strings"

	"golang.org/x/net/html"
	"golang.org/x/net/html/atom"
)

func main() {
	// Error handling omitted for brevity.

	const content = `<p>
	<a href="https://example.com">Not External</a>
	<a href="https://furqansoftware.com">External</a>
</p>`

	// Parse the HTML.
	doc, _ := html.Parse(strings.NewReader(content))

	// Walk the entire HTML tree.
	Walk(doc, func(n *html.Node) {
		if n.Type == html.ElementNode && n.DataAtom == atom.A && IsExternal(GetAttr(n, "href")) {
			// Set attributes on all anchors with external links.
			SetAttr(n, "target", "_blank")
			SetAttr(n, "rel", "noreferrer noopener")
		}
	})

	// Render the modified HTML.
	b := bytes.Buffer{}
	html.Render(&b, doc)
	fmt.Println(b.String())
	// Output:
	// <html><head></head><body><p>
	// 	<a href="https://example.com">Not External</a>
	// 	<a href="https://furqansoftware.com" target="_blank" rel="noreferrer noopener">External</a>
	// </p></body></html>
}

// Walk traverses the entire HTML tree and calls fn on each node.
func Walk(n *html.Node, fn func(*html.Node)) {
	if n == nil {
		return
	}
	fn(n)

	// Each node has a pointer to its first child and next sibling. To traverse
	// all children of a node, we need to start from its first child and then
	// traverse the next sibling until nil.
	for c := n.FirstChild; c != nil; c = c.NextSibling {
		Walk(c, fn)
	}
}

// GetAttr returns the attribute on a node by its key.
func GetAttr(n *html.Node, key string) string {
	for _, a := range n.Attr {
		if a.Key == key {
			return a.Val
		}
	}
	return ""
}

// SetAttr sets an attribute on a node.
func SetAttr(n *html.Node, key, val string) {
	for i := range n.Attr {
		a := &n.Attr[i]
		if a.Key == key {
			a.Val = val
			return
		}
	}
	n.Attr = append(n.Attr, html.Attribute{
		Key: key,
		Val: val,
	})
}

// IsExternal returns true if url doesn't have "https://example.com" as the
// prefix. You can do better than this.
func IsExternal(url string) bool {
	return !strings.HasPrefix(url, "https://example.com")
}

Why Is The Output An Entire HTML Document?

Any HTML you parse is treated as an entire document. But more often than not, when dealing with user-generated content, you are probably dealing with an HTML fragment.

Bump Calendar Versioning (CalVer) Bash Script for Git

m@hjr265.me (Mahmud Ridwan) — Mon, 05 Dec 2022 09:00:00 +0600

For Toph, SemVer didn’t make much sense. CalVer did.

Toph is closed-source and available to users as a SaaS. We are not trying to maintain or communicate backwards-compatible/incompatible changes to Toph with our users. With CalVer (short for Calender Versioning), the versioning would be tied to the release date.

The pattern we wanted to use: {YYYY}.{0M}.{SEQ}.

{YYYY}: Four-digit year.
{0M}: Zero-padded month.
{SEQ}: Starts from 0. Goes up by 1 for each bump. Resets after the end of the month.

For example: 2022.12.3.

Single Node MongoDB Replica Set with Docker Compose

m@hjr265.me (Mahmud Ridwan) — Sun, 04 Dec 2022 15:00:00 +0600

Toph needs a few MongoDB features that only work in replica set mode. Take Change Streams, for example. It is unavailable in standalone mode.

To ease development, all of Toph’s application codebases come with Docker Compose files. With just a single docker-compose up, I can have any of Toph’s applications running in a development environment. But having MongoDB start in replica set mode has been a bit of work.

You see, simply starting three nodes and then going in to configure them to be in a replica set wasn’t something I wanted to do. I wanted only a single node to run, and I wanted it to start in replica mode, even if I was running docker-compose up on a freshly installed machine.

Grid Chart for Toph's One Million Submissions

m@hjr265.me (Mahmud Ridwan) — Wed, 30 Nov 2022 09:50:00 +0600

Toph recently reached a milestone my family and I have been looking forward to. One million submissions. It may be a small win, but it is that sweet reward of working on your favourite project.

On the relevant Toph Blog post, we have a picture that is 3840×25982 pixels and has one million coloured squares on it. The squares represent the one million submissions and are green for correct (Accepted) submissions and red for any other incorrect (Wrong Answer, CPU Limit Exceeded, etc.) submissions.

Showing GitHub Stars With Static Site Generator Hugo

m@hjr265.me (Mahmud Ridwan) — Sun, 27 Nov 2022 20:13:00 +0600

Static site generators are one of my favourite things about the Internet. I remember when almost every website built around me was based on Joomla or WordPress. I dread that time.

My website, which you are on right now, is built with Hugo. I have a page on this website listing some of my open-source projects. And I wanted an easy way to show the number of GitHub stars on my Hugo-based website for my open-source projects.

Passing A Vector of RedisModuleString to RedisModule_Call

m@hjr265.me (Mahmud Ridwan) — Sat, 26 Nov 2022 08:00:00 +0600

While building Redis Too (a recommendation engine module for Redis), I spent a good bit of time (and strands of hair) figuring out how to pass a variable number of arguments to a Redis command like “SUNION”.

The format specified of the RedisModule_Call function accepts ‘v’ to denote “a vector of RedisModuleString”. But to use it, you need to pass two arguments to RedisModule_Call: the array of RedisModuleString and the size of the array.

Extracting Text From PDF Using Go

m@hjr265.me (Mahmud Ridwan) — Mon, 14 Nov 2022 06:09:00 +0600

TL;DR: Read all text values from PDF, ordered by Y-position. Make a state machine. The link to the complete code is at the end of the article.

When it comes to extracting text from PDF, you will likely face one of these two scenarios:

The PDF you generate or export from some software where all the text is still text.
The PDF you scan from a physical document, and what you have is an image in a PDF document.

If it is a scanned PDF, this is an Optical Character Recognition (OCR) task. You will need to use a tool like Tesseract to extract the text from the image.

Updating Creality CR-10 Smart Firmware

m@hjr265.me (Mahmud Ridwan) — Thu, 21 Oct 2021 17:25:00 +0600

There seems to be a lot of frustration with this 3D printer. And one of those frustration stems from how confusing the firmware update process is. The documentation is lacking in terms of some of the details.

To keep things simple, here are the important bits:

Updating the firmware of this 3D printer involves two separate steps. The first one is to update the firmware of the hardware. The second one is to update the firmware of the screen.

Stream Uploading Files to S3 with Object Writer

m@hjr265.me (Mahmud Ridwan) — Sun, 06 Jun 2021 09:50:00 +0600

The official AWS SDK provides an upload manager construct that allows you to upload to S3 from any io.Reader. Using it is straightforward, that is until you need to create and upload a potentially large ZIP file.

The solution: use the upload manager with a pipe.

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// Open a pipe.
pr, pw := io.Pipe()

errch := make(chan error)

// Upload from pr in a separate Go routine.
go func() {
	_, err := s3manager.NewUploader(awssess).Upload(&s3manager.UploadInput{
		Bucket: aws.String("brain-bucket"),
		Key: aws.String("blobs/very-large.zip"),
		Body: pr,
	})
	errch <- err
}()

// Create a ZIP writer around pw.
zw := zip.NewWriter(pw)

// Add stuff to zip.

zw.Close() // Finishes the ZIP.

pw.Close() // Closes pw, marks EOF in pr.

err := <-errch // If err == nil, success.

For convenience, I have wrapped this up in a Go package: github.com/hjr265/s3ow [ GitHub ].

Using Language Servers with CodeMirror 6

m@hjr265.me (Mahmud Ridwan) — Sun, 28 Mar 2021 13:36:59 +0600

CodeMirror 6, a rewrite of the CodeMirror editor, brings several improvements. Toph has been using CodeMirror for its integrated code editor since its introduction.

As CodeMirror 6 reached a stable interface with the promise of better touchscreen support, it was time for an upgrade! During which I wanted to introduce language server support.

The goal was to provide code completion, diagnostics, and hover tooltips. And, CodeMirror 6 makes it easy to do all three.

Should I Even Eat That Onion?

m@hjr265.me (Mahmud Ridwan) — Sun, 28 May 2017 00:00:00 +0600

This is just a long overdue rant.

A little over a year ago, I ordered a power bank from a very reputable online store. Compared to my previous experiences with other stores, they seemed super professional. I received a phone call from them to get the order confirmed, and a couple of days later they delivered it right to my doorstep.

Amazing service! Except, what I received was a fake product.

Building a Recommendation Engine

m@hjr265.me (Mahmud Ridwan) — Fri, 06 Feb 2015 00:00:00 +0600

Ever wondered how a recommendation engine works? I did. Turns out, the mechanics involved in generating recommendations is actually pretty neat! You can learn more about it in the article I wrote for Toptal on the anatomy of a simple recommendation engine.

tar

m@hjr265.me (Mahmud Ridwan) — Tue, 26 Aug 2014 00:00:00 +0600

Tar is a file format that allows you to archive files and directories while preserving flags and other file information. Tar is also the name of the Unix utility that manipulates these files and is also popular for being notoriously enigmatic.

Did you know? Tar, the name, is derived from “tape archive”.

But Ridwan, I don’t store my files on tapes. Do I need tar?

Well, if you need to ask that question (and don’t care about helping Rob disarm the bomb), then the answer may just be “no”. But if you spend enough time in Unix-like systems, you are bound to come across a “.tar” file eventually.

Using an external USB drive for the root file system of a Raspberry Pi

m@hjr265.me (Mahmud Ridwan) — Tue, 14 Jan 2014 00:00:00 +0600

By design, a Raspberry Pi always requires an SD card to boot from. But one can still have its root partition located on an external storage device. Be it for reasons involving speed improvement, or avoid challenging the write endurance of an SD card.

The details in the following steps may vary based on the distribution of Linux being used, but the fundamental idea should be similar anyway:

Assuming a distribution of Linux is already installed on the SD card, use it to boot a Raspberry Pi up.

Hello World

m@hjr265.me (Mahmud Ridwan) — Sat, 28 Dec 2013 00:00:00 +0600

Just a few hours ago I didn’t even know that I would suddenly have the urge to write. Heck! I didn’t even know that I would be creating a blog for that. But now that my first post is live, I guess I will have to make it a habit.

The first post is definitely about saying “hello”. And I thought, what better way is there to say that than to say it in different languages: Bash, C, C#, C++, Go, Java, JavaScript, Perl, PHP, Python, VisualBasic

Experience

m@hjr265.me (Mahmud Ridwan) — Mon, 01 Jan 0001 00:00:00 +0000

Firefox's Screenshot Command

m@hjr265.me (Mahmud Ridwan) — Mon, 01 Jan 0001 00:00:00 +0000

I needed to capture a HiDPI screenshot in Firefox without switching to a device with a HiDPI display. I was wondering if that was even possible. While searching for a how-to, I came across this :screenshot web console helper function.

How is it that I didn’t know about it for so many years? 🤯

This function has been in existence for about 7-8 years. And it has a bunch of handy options.

MTR: Not An Ordinary Network Diagnostic Tool

m@hjr265.me (Mahmud Ridwan) — Mon, 01 Jan 0001 00:00:00 +0000

MTR combines the functionality of the traceroute and ping programs in a single network diagnostic tool. And, I am certain internet service providers (ISPs) of third-world countries hate it when customers discover this tool.

I came across the tool again recently while investigating a WireGuard connection issue between an on-premises Toph server and one in Singapore.

Was it our router? Was it Linode’s infrastructure? Was it our local ISP?

A quick mtr command solved the mystery:

Publications

m@hjr265.me (Mahmud Ridwan) — Mon, 01 Jan 0001 00:00:00 +0000

Timeline

m@hjr265.me (Mahmud Ridwan) — Mon, 01 Jan 0001 00:00:00 +0000

Mahmud Ridwan (hjr265) on hjr265.me

Papyrus

Toph

CodeMarshal

Redsync

Drafts

Bullet

Cactus

Node WHOIS

Trace

μTools

CodeMirror LanguageServer

Loadcat

GitTop

Printd

Scanlib

Too

Brdgd

Dots

Now

Can AI Take a Software Engineer's Job?

My First Fully Agentic Coding Project: GitTop

Resurrecting a 12-Year-Old Node.js Project With Claude Code

Ditching MongoDB Text Indexes for Edge N-Grams

The Problem With MongoDB Text Indexes

Strangest AMD Ryzen 7950x Bug

All Our Customer Care Agents Are Busy at This Moment

How Hard Can It Be: Use JavaScript to Close Web Browser Window After Print

Attempt 1: Call window.close() Immediately After window.print()

Remmina SPICE SSH Tunnel Bug and a Workaround

Bug

#100DaysToOffload Milestone: The 100th Blog Post

Android Emulator Slow As a Snail; Reason BTRFS

Check If a WireGuard Connection Is Up

Scanning a Website for Broken Links in Go

When Was the Last Time Technology Blew Your Mind?

Go Web Server for Remotely Powering on a Desktop Computer With a Raspberry Pi

7 Useful io.Reader and io.Writer Wrappers in Go

Forwarding a Port Over SSH in Go

Strange Hugo Bug and How to Work Around It

Serving JSON in Go with http.ServeContent

Editing an SVG Icon to Be Resize-friendly

Testing a Go Package That Depends on Redis

Tracking io.Copy Progress in Go

Responsive Activity Chart With Chart.js

Multi-threaded Downloads in Go

Building Advanced Search With Go and MongoDB

Backing up Self-hosted GitLab With Ansible

JavaScript window.close Won't Close the Window

Adding Anchor Links Next to Headings in Hugo

Setting Up Prometheus DNS-SRV Discovery with Terraform and DNSimple

Waiting for an HTTP Service in GitLab CI/CD

SOCKS Proxy Over SSH

Are There Three Types of #100DaysToOffload Challengers?

Uploading Files Over SSH in Go

Steam Link Black Screen on a Retro Pie Raspberry Pi 4

Synchronization Constructs in the Go Standard Library

Counter

Powering on a Desktop Computer Remotely With a Raspberry Pi

Serving hjr265.me From an S3-like Bucket Using a Caddy Module

Why Both?

Switch Monitor Input from Linux Command Line

Making a Real-time "Last N Days" Leaderboard with MongoDB Aggregation Framework

The Naive Way

Windows Is Weird

Show a Log Throbber in Terminal with Go

Not a "High-rated" Person

Gnome Not Reporting Bluetooth Earbuds Battery? Enable the D-Bus Interface

#100DaysToOffload Milestone: The 67th Blog Post

10 Forms of Bash Shell Parameter Expansion

Parsing Social Media URLs in Go With Slinky

Fixing Creality CR-10 Smart Touch Screen Orientation Issue

Bash Script to Auto-archive Downloads by Date

Stardew Valley and Eric Barone

Stardew Valley

Building a Blog With Hugo

Setup HTTP3 with NGINX Mainline

Installing NGINX Mainline

Prevent Git Commits with Unformatted Go Code

Mattermost (or Slack) Message on SSH Login

Attempt 1: Call `window.close()` Immediately After `window.print()`