dspinellis

URL=https://www.spinellis.gr/unix

love: # Help: Create a file name love
	touch love

money: # Help: Hit the jackpot
	yes $$ | fmt | head

me a wizard: MOOC # Help: Become a Unix command-line wizard

kpirliyev

PostgreSQL 13 Master-Standby Streaming Replication

PostgreSQL has various types of replication available and it could be a little bit confusing to figure out what has to be done to just configure a simple master-standby replicated database setup. Digging my way through documentation I decided to write my own little guide on how to setup simple replication in PostgreSQL 13.

How it works

Streaming replication works by streaming the contents of WAL (Write-Ahead Logging) file from one server to another. Each transaction is first written into the WAL file, so essentially every change on the primary server will be replicated on the standby server. Standby server could be used for read-only operations, but can't be written to. Ofcourse, transferring data over the network takes time and there is a small lag before data written to one server becomes available on the other. To guarrantee data consistency on both servers at the time of read operation we can enable synchronous replication mode. This way, datab

quephird

SQL Tricks

Contents

• Purpose
• Nota bene
• Example schema
• Selecting records
  • How do I get a list of items and the sum of another column in a table?
  • How do I concatenate a list of string values each relavant to a row?
• How do I get a list of items and filter the result set on some aggregate?

mahemoff

Vim has a Terminal Mode!

Since v8.1 (May 2018), Vim has shipped with a built-in terminal. See https://vimhelp.org/terminal.txt.html or type :help terminal for more info.

Why use this? Mainly because it saves you jumping to a separate terminal window. You can also use Vim commands to manipulate a shell session and easily transfer clipboard content between the terminal and files you're working on.

Key Bindings

narrowtux

defmodule Model do
  schema "models" do
    field :foo, :string
    has_many :children, Model, foreign_key: :parent_id
    belongs_to :parent, Model, foreign_key: :parent_id
  end
  
  @doc """
    Recursively loads parents into the given struct until it hits nil
  """

tooky

# Corey's challenge is to make the second test pass without ever making the first test fail.
# run ruby stack.rb to run the tests
# For more information see http://tooky.co.uk/kickstart-academy-podcast-with-corey-haines-and-sandi-metz/

class Stack
  def empty?
    true
  end
  def push(element)
    @empty = false

lelandbatey

Description

This simple script will take a picture of a whiteboard and use parts of the ImageMagick library with sane defaults to clean it up tremendously.

The script is here:

#!/bin/bash
convert "$1" -morphology Convolve DoG:15,100,0 -negate -normalize -blur 0x1 -channel RBG -level 60%,91%,0.1 "$2"

Results

Odaeus

class ApplicationController < ActionController::Base
  # Creates an accessor which is exposed to the view
  def self.view_accessor(*names)
    attr_accessor *names
    helper_method *names
  end
end

aslakhellesoy

#!/bin/sh
# Compile and show [GFM](https://help.github.com/articles/github-flavored-markdown) docs in your browser.
# Before this works you need to `gem install bcat`
#
# Usage: gfm.sh FILE.md
#

curl --silent --data-binary @- https://api.github.com/markdown/raw -H "Content-Type: text/plain" | bcat

andkerosine

$stack, $draws = [], {}

def method_missing *args
  return if args[0][/^to_/]
  $stack << args.map { |a| a or $stack.pop }
  $draws[$stack.pop(2)[0][0]] = args[1] if args[0] == :<
end

class Array
  def +@