The Blurb

I scripted in bash/go alot.

Links:

• the small random ones
• zet
• list
• magellan - wip

The Dream

So I’ve had this dream for a really long time…

Imagine a system where you could build really small apis and link them together in order to create really complex behavior, and you could use timers to run those linked apis on a timer and ohmygoditwouldbeamazing.

So for about a year I went down the rabbit hole of kubernetes, argo, distributed computing, and more. Turns out that building a Jarvis is hard… and expensive.

After another year of doing other things, and noodling on how to do any of this I stumbled upon a video by rwxrob, he talked about how you could use filters to transform text in vim. And that was all I needed tip the boulder that sent me tumbling down the scripting rabbit hole.

3 weeks later

I have discovered just how cracked linux’s Unix Philosophy really is specifically bash filters. It’s

Turns out my dream had already been designed, implemented, open sourced, and made completely free by some Finnish Dude in the 90’s. Go figure.

Anyway bash filters are awesome so I’m gonna do a bit of a dive into em here mostly for my own entertainment.

What is filter

A filter in it’s basic form is pretty simple. It’s any command that takes input data from the standard input and outputs the result to standard output.

Why is filter

This was the part that made this click for me. Basically remember how I talked about writing those small apis and hooking them together in complex ways, well it effectively achieves that. By standardizing the way program ingest and output data you can write small specialized commands and then link them together to get remarkably complex behaviors.

How is filter

Filters are trivially easy. As an example I’ll build out a simple filter that will comment out any lines passed to it.

Step 1: Read text from standard in

In bash we do this with the read command (see man read) to learn more. For our case we’ll read in a loop each line we get in.

#!/bin/bash

while read line

Step 2: Do something with that text

In our example we want to comment out the line so lets do that.

#!/bin/bash

while read line
do 
    newline="# $line"

Step 3: Spit the text back out to standard out

Also simple.

#!/bin/bash

while read line
do 
    newline="# $line"
    echo $newline"
done;

Test it

I saved the code above into a file named comment and made it executable.

arjun@stupid:~ $ echo -e 'hello\nhi\nbye\nbye' | ./comment '#'
# hello
# hi
# bye
# bye

Yay it worked, writing filters get’s way more complex than this but the core concepts are pretty simple. You can do all sorts of crazy things like building snippet tools, adding emojis to text and more!

Have fun in the rabbit hole.

Links:

ps. Here’s links to all my scripts that I’ve made or am working on.

• the small random ones
• zet
• list
• magellan - wip