Toby Devlin

Database engineers hate this one weird trick

databases, bash

Implementing The World’s Worst Database.

Modern databases seem like magic—until you realize they're just organized files and clever processes. Let's cut through the mystique by building a key-value database in bash. Spoiler: it's shockingly simple... but impractical.

Here's What We're Gonna Do

We'll create four bash functions that handle CRUD operations (Create, Read, Update, Delete). No frameworks, no dependencies—just pure shell magic.

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# Initialize our "database"  
mkdir -p ~/.database

Heres the reall magic:

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# Create/update a key-value pair  
dbset() { echo "$2" > ~/.database/"$1"; }  

# Read a value by key  
dbget() { cat ~/.database/"$1"; }  

# Delete a key  
dbdelete() { rm ~/.database/"$1"; }

# Search for keys by pattern  
dbscan() { ls -l ~/.database | grep "$1"; }

Boom. You've just deployed a database. Let's break it down.

1. How It Works

File-Based Storage

Every "key" is a file in ~/.database, and its "value" is the file's content. Writing to a key? Just echo text into a file. Reading? Cat the file.

Atomic Operations

Each command runs as a single filesystem operation—no half-written data.

2. ACID Compliance: The Delusional Developer's Checklist

Let's pretend we're enterprise-grade! Here's how our bash DB technically checks ACID boxes:

  • Atomicity
    Kinda. Each dbset or dbdelete is a single filesystem operation. Your whole value writes or fails—no partial updates.
  • Consistency
    Sure, if you squint. Files either exist with valid content or don't. No constraints? No problem!
  • Isolation
    Single-player mode. The OS handles file locks, but concurrency? Let’s not talk about concurrency.
  • Durability
    As durable as your disk. If your SSD survives, so does your data.
Warning: This is a joke. Real databases handle ACID with transactions, locks, and recovery mechanisms. Don't use this for anything serious.

3. Bonus Round: Hooks and Permissions

Trigger Happy

Want to run code when a key changes? Use inotify-tools to watch the directory:

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# Watch for file changes in real-time  
inotifywait -m ~/.database | while read event; do  
  echo "Database updated! Event: $event"  
done

Security Features

Permissions? Just use UNIX file permissions. Want to restrict access to a key?

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chmod 600 ~/.database/my_secret_key  # Only you can read/write

4. Why This Is Terrifying

  • No backups
  • No transactions
  • No scalability
  • No error handling (What if two processes write at once?)

But hey—it's 4 lines of code.

Conclusion: A Glorious Toy

Congratulations! You've built a "database" that's both awe-inspiring and horrifying. While this isn't replacing PostgreSQL anytime soon, it demystifies core database concepts:

  • Data is just organized bytes
  • "Queries" are operations on those bytes
  • Permissions and hooks are OS-level features

Go forth and experiment — then use a real database for your next project.

Final Warning: If you deploy this, you'll anger the ops gods. You've been warned.
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