Moorthi almoorthi

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

Atom Clojure Setup

This describes how I setup Atom for an ideal Clojure development workflow. This fixes indentation on newlines, handles parentheses, etc. The keybinding settings for enter (in keymap.cson) are important to get proper newlines with indentation at the right level. There are other helpers in init.coffee and keymap.cson that are useful for cutting, copying, pasting, deleting, and indenting Lisp expressions.

Install Atom

Download Atom

The Atom documentation is excellent. It's highly worth reading the flight manual.

	#!/usr/bin/perl
	# Easy port scanner
	# I wrote this in the 90s to help learn socket programming
	# ./quickscan -h for usage

	use Socket;

	$\| = 1; # so \r works right

	my ($ip, $protocol, $port, $myhouse, $yourhouse, $log);

	<?php
	/**
	* This is an example of a practical encoder and decoder for base-62 data in PHP
	* It differs from the majority of examples in that it's fast enough for moderate data sizes, unlike multiprecision converters
	* To be practical, base-62 encoding needs to use internal chunking and padding because base-62 does not fit exactly into any integral number of bits
	* This means the output is not quite compatible with multiprecision conversions,
	* but the encoded data retains all the desirable properties of base-62, so (unlike any base-64 encoding) it's URL, DNS, email address and pathname safe
	* @author Marcus Bointon <[email protected]>
	* @copyright 2011 Marcus Bointon
	* @license http://www.opensource.org/licenses/mit-license.html MIT License

	Useful One-Line Scripts for Perl Jan 28 2012 \| version 1.08
	-------------------------------- ----------- ------------

	Compiled by Peteris Krumins ([email protected], @pkrumins on Twitter)
	http://www.catonmat.net -- good coders code, great reuse

	Latest version of this file is always at:

	http://www.catonmat.net/download/perl1line.txt

	First, create a couple new folders:

	cd ~/
	mkdir Scripts
	mkdir Screenshots
	cd Screenshots
	mkdir cron

	cd ~/Scripts
	vim screencapture.sh

	package main

	import (
	"fmt"
	)

	func decorator(f func(s string)) func(s string) {

	return func(s string) {
	fmt.Println("Started")

	# create a 4G swap file at /swapfile
	sudo fallocate -l 4G /swapfile
	sudo chmod 600 /swapfile
	sudo mkswap /swapfile
	sudo swapon /swapfile

	# Make the Swap File Permanent
	sudo echo "/swapfile none swap sw 0 0" >> /etc/fstab

	# set swappiness to 10

	#!/bin/bash

	# setup AWS CLI first
	# http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-set-up.html

	# configure AWS CLI (e.g. use IAM role for S3 access)
	export AWS_DEFAULT_REGION=us-east-1
	export AWS_ACCESS_KEY_ID=IDHERE
	export AWS_SECRET_ACCESS_KEY=KeyHere

	//Values and definitions

	val x = 5 // constant, evaluated once
	def y = 5 // definition (function), evaluated at each call
	lazy val z = 5 // constant with lazy evaluation
	var v = 5 // variable, only use when really needed

	//Control constructs

	if (true) 1 else 2 // conditional _expression_, of type Int