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> Use this file to discover other available public pages before exploring further.

# LHB Linux Digest #26.12: Demystifying diff, Process Substitution, History Trick, and More
- URL: https://linuxhandbook.com/newsletter/26-12/
- Published: 2026-09-11T11:59:04.000Z
- Updated: 2026-09-11T11:59:04.000Z
- Description: Keep on Linux-ing :)
- Author: Abhishek Prakash
- Tags: Newsletter

Last week, we revealed the [Free Tmux course](https://linuxhandbook.com/courses/tmux/). I am also working on creating roadmaps so that members can follow a dedicated learning path with all the resources we have created in the last 8 years. 

Next week, we should have the GitOps course, focusing on ArgoCD. This will build upon the foundation of the [Git basics course](https://linuxhandbook.com/courses/git/). 

## Essential Linux concept: diff

All that Git talk actually rests on a very old, very simple Linux idea. You compare two versions of something, and then you act on the difference.

That's exactly what the [diff command](https://linuxhandbook.com/diff-command/) does. You give it two files, and it tells you what you'd need to change in one to make it match the other. It's the same mental model your version control uses under the hood.

The output looks cryptic the first time you meet it, with things like `2c2`, `3a4` and `5d5`. Once you learn to read it, it makes complete sense. We explain the output line by line in [this guide](https://linuxhandbook.com/diff-command/).

Here's the part most of us forget: `diff` isn't limited to single files. With `diff -r` you can [compare two entire directories](https://linuxhandbook.com/compare-directories/) and spot exactly how two config folders drifted apart. And if you find yourself creating temporary files just to compare two command outputs, [process substitution](https://linuxhandbook.com/bash-process-substitution/) lets you do it in one line: `diff <(command1) <(command2)`.

## **💡**Quick terminal tip

Using history expansions like `!$` (last argument) or `!!` (entire previous command) can feel like a gamble when running destructive operations. You only see what it resolved to after you have pressed the Enter key.

Bind Readline's magic-space to expand history references instantly as soon as you press the Spacebar:

Open the `~/.inputrc` file and add the following line at the end.

```bash
Space: magic-space

```

Restart the terminal session.

When you type `sudo !!` or `rm -rf !$` and hit Space, the shell immediately replaces the tokens with the full command string right in front of your eyes. You can review, edit, or back out before executing, eliminating both keystrokes and blind execution risk.

![](https://linuxhandbook.com/content/images/2026/09/expansion.gif)

## 🛠️ Tool discovery

Let's see if you find your next favorite tool.

### Monoscope: Open-Source Observability and Trace Aggregator for Distributed Microservices

[Monoscope](https://github.com/monoscope-tech/monoscope?ref=linuxhandbook.com) is an open-source observability engine tailored for developers needing unified log, metric, and distributed trace visibility across local containers and multi-service staging environments.

[GitHub - monoscope-tech/monoscope: Monoscope lets you ingest and explore your logs, traces and metrics. We store these in S3 compatible buckets. Query in natural language via LLMs.Monoscope lets you ingest and explore your logs, traces and metrics. We store these in S3 compatible buckets. Query in natural language via LLMs. - monoscope-tech/monoscope![](https://linuxhandbook.com/content/images/icon/favicon-52635665-88cc-48f3-9bb3-5a9f57fd4f90.png)GitHubmonoscope-tech![](https://linuxhandbook.com/content/images/thumbnail/monoscope-a2663e6d-d664-4511-b443-11fc5bc54be8)](https://github.com/monoscope-tech/monoscope?ref=linuxhandbook.com)

### Colanode: Open-Source, Local-First Collaboration Workspace

[Colanode](https://github.com/colanode/colanode?ref=linuxhandbook.com) is an open-source, local-first collaboration platform designed to unify documents, structured databases, real-time chat, and file management under a self-hosted architecture.

[GitHub - colanode/colanode: Open-source and local-first Slack and Notion alternative that puts you in control of your dataOpen-source and local-first Slack and Notion alternative that puts you in control of your data - colanode/colanode![](https://linuxhandbook.com/content/images/icon/favicon-2dfbdc72-08ac-4300-b39b-c57ba9001e03.png)GitHubcolanode![](https://linuxhandbook.com/content/images/thumbnail/colanode-89234355-a983-4274-92b2-23ab8a3ee963)](https://github.com/colanode/colanode?ref=linuxhandbook.com)

## 📣 Event alert

AGNTCon + MCPCon Europe is happening in Amsterdam on 17–18 September, and if you're building anything in the agentic AI or MCP space, this is the event to attend.

The event is full of open source maintainers, enterprise engineers, infra and tooling folks, and researchers. 

You'll bump into the people building MCP itself, alongside teams from AWS, Google, Hugging Face, Microsoft, Anthropic, Solo.io, and a long list of startups exploring Agentic AI.

**You can knock off your ticket prices with code ITSFOSS\_50.**

🗓 17–18 September  
📍 RAI Amsterdam

[Register for AGNTCon + MCPCon Europe](https://events.linuxfoundation.org/agntcon-mcpcon-europe/?ref=linuxhandbook.com)

## 📰 Linux news that matters

- [Broadcom has quietly removed all public download pages for the VMware Virtual Disk Development Kit (VDDK)](https://itsfoss.com/news/broadcom-removes-vmware-vddk-downloads/?ref=linuxhandbook.com), restricting future access exclusively to authorized Technology Alliance partners.
- [Threat actors are actively breaching F5 BIG-IP APM appliances](https://www.bleepingcomputer.com/news/security/hackers-breach-f5-big-ip-apm-devices-to-deploy-linux-rootkit/?ref=linuxhandbook.com) to deploy "PoisonedRefresh," a stealthy Linux rootkit that persists across firmware upgrades and modifies SELinux policies.
- [CERN is migrating over 2,200 accelerator control computers to Debian 13](https://itsfoss.com/news/cern-debian-push/?ref=linuxhandbook.com) to bypass restrictive enterprise CPU requirements and modernize hardware lifecycle management. In a parallel push toward digital sovereignty, the [Swiss government has launched a CHF 9 million pilot](https://itsfoss.com/news/switzerland-replace-microssoft-pilot/?ref=linuxhandbook.com) deploying openDesk to replace Microsoft 365 across 3,000 federal workstations.
- [Intel's Dynamic PAMT support has been queued in the x86/tdx tree for Linux 7.4](https://www.phoronix.com/news/Intel-Dynamic-PAMT-For-7.4?ref=linuxhandbook.com), reducing the \~0.4% baseline memory overhead required by Trust Domain Extensions by allocating the Physical Address Metadata Table dynamically rather than upfront.
- [Google has open-sourced Mantis under Apache 2.0](https://www.marktechpost.com/2026/09/09/google-open-sources-mantis-a-modular-skills-toolkit-that-lets-coding-agents-find-reproduce-and-patch-vulnerabilities/?ref=linuxhandbook.com), providing a modular framework of slash-command skills that enables AI coding agents to manage end-to-end vulnerability triage.

## 😂 Geek humor

![](https://linuxhandbook.com/content/images/2026/09/linuxhandbook_meme_september_2.jpg)

## 💌 Keep on loving Linux Handbook

GitOps course is nearly ready. It should arrive next week. 

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