zuigon

PSQL

Magic words:

psql -U postgres

Some interesting flags (to see all, use -h or --help depending on your psql version):

-E: will describe the underlaying queries of the \ commands (cool for learning!)
-l: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)

Let's say you have a Bash shell script, and you need to run a series of operations on another system (such as via ssh). There are a couple of ways to do this.

First, you can stage a child script on the remote system, then call it, passing along appropriate parameters. The problem with this is you will need to manually keep the remote script updated whenever you change it -- could be a bit of a challenge when you have something to execute on a number of remote servers (i.e., you have a backup script running on a central host, and it needs to put remote databases in hot backup mode before backing them up).

Another option is to embed the commands you want to run remotely within the ssh command line. But then you run into issues with escaping special characters, quoting, etc. This is ok if you only have a couple commands to run, but if it is a complex piece of Bash code, it can get a bit unwieldy.

So, to solve this, you can use a technique called rpcsh -- rpc in shell script, as follows:

First, place th

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns                     on recent CPU
L2 cache reference ........................... 7 ns                     14x L1 cache
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns                     20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs 4X memory

Others have recently developed packages for this same functionality, and done it better than anything I could do. Use the packages instead of this script:

Gargoyle package by @lantis1008
OpenWRT package by @dibdot

Description

In its basic usage, this script will modify the router such that blocked addresses are null routed and unreachable. Since the address blocklist is full of advertising, malware, and tracking servers, this setup is generally a good thing. In addition, the router will update the blocklist weekly. However, the blocking is leaky, so do not expect everything to be blocked.

	# vim: set softtabstop=2 tabstop=2 shiftwidth=2 expandtab autoindent syntax=nix nocompatible :
	# Containers

	{ config, pkgs, ... }:

	{ containers.browser =
	let hostAddr = "192.168.100.10";
	in
	{ privateNetwork = true;
	hostAddress = hostAddr;

	{-# LANGUAGE FlexibleInstances, GeneralizedNewtypeDeriving #-}


	newtype TimeUnit = TimeUnit Integer -- how many microseconds
	deriving (Eq, Show, Num)

	instance Num (TimeUnit -> TimeUnit) where
	fromInteger n = \(TimeUnit scale) -> TimeUnit (n * scale)
	-- a + b = ... -- task for you

	# Install ARCH Linux with encrypted file-system and UEFI
	# The official installation guide (https://wiki.archlinux.org/index.php/Installation_Guide) contains a more verbose description.

	# Download the archiso image from https://www.archlinux.org/
	# Copy to a usb-drive
	dd if=archlinux.img of=/dev/sdX bs=16M && sync # on linux

	# Boot from the usb. If the usb fails to boot, make sure that secure boot is disabled in the BIOS configuration.

	# Set swedish keymap

	#!/usr/bin/env bash

	#
	# This is sp, the command-line Spotify controller. It talks to a running
	# instance of the Spotify Linux client over dbus, providing an interface not
	# unlike mpc.
	#
	# Put differently, it allows you to control Spotify without leaving the comfort
	# of your command line, and without a custom client or Premium subscription.
	#

	#!/usr/bin/python2

	import logging
	import sys
	import couchdb
	import json
	from libgreader import GoogleReader, ClientAuthMethod, Feed

	"""
	Original can be obtained here: https://gist.github.com/Nazgolze/5479539

	#!/opt/local/Library/Frameworks/Python.framework/Versions/2.6/bin/python

	import urllib,json
	import argparse
	parser = argparse.ArgumentParser()
	parser.add_argument( 'subreddit', nargs=1,help="Subreddit to browse, f.e. programming")
	args= parser.parse_args()
	subreddit = args.subreddit[0]
	a = urllib.urlopen('http://www.reddit.com/r/'+str(subreddit)+'/.json')
	try: