Winston Kotzan wakproductions

File System

`chmod` & `chown`

chmod: 1=x, 2=w, 4=r

chmod (user)(group)(other) chmod 730 # only the user can rwx, read permission to the group or other

chown owner:group file

Show ActiveRecord SQL

Sometimes SQL doesn't show up in test environment or development. This turns it back on:

ActiveRecord::Base.logger = Logger.new(STDOUT)

Rails Database Config

config = Rails.configuration.database_configuration

Server Setup

The IP Address binding needs to be set in the /etc/redis/redis.conf for it to be available.

Start Server

sudo service redis-server start

Restart Postgres (on Linux core installation via apt)

sudo service postgresql restart

Show databases

wkotzan=# \l

Function syntaxes

def myfunc(a,b) do
  a + b
end

lambda:
myfunc = fn a, b -> a + b end
myfunc.() # this is one way to call a lambda

Things that jumped out at me while learning Elixir

Cons operator

In addition to the aforementioned functions, you can use pattern matching and the cons operator | to split a list into head and tail; we’ll learn more about this pattern in later lessons:

iex> [h|t] = [3.14, :pie, "Apple"]
[3.14, :pie, "Apple"]
iex&gt; h

Useful Modules

formidable - for receiving forms and HTTP files
nodemailer - email
standard - code linter
passport - equivalent of Devise
knex -> Ruby Arel?
sequelize -> ORM like ActiveRecord? (how does it interface with Knex?)
Gulp -> ???
nodemon -> Ruby guard?

Get request

Download file

curl -o website https://domain.com curl -O https://domain.com/file.zip

Header Only

curl -I http://domain.com

	#!/bin/bash

	#
	# copy this into /etc/profile.d/instance-name-tag.sh
	#
	# you will need:
	# - curl, jq, and aws cli installed
	# - an IAM role that gives the EC2 instance access to describe tags
	#

	-- show running queries (pre 9.2)
	SELECT procpid, age(query_start, clock_timestamp()), usename, current_query
	FROM pg_stat_activity
	WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%'
	ORDER BY query_start desc;

	-- show running queries (9.2)
	SELECT pid, age(query_start, clock_timestamp()), usename, query
	FROM pg_stat_activity
	WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'