timvisee

Falsehoods programmers believe about time

This is a compiled list of falsehoods programmers tend to believe about working with time.

Don't re-invent a date time library yourself. If you think you understand everything about time, you're probably doing it wrong.

Falsehoods

• There are always 24 hours in a day.
• February is always 28 days long.
• Any 24-hour period will always begin and end in the same day (or week, or month).

Unnumbered

def rename_collection(old_name, new_name, drop_target=false)
  client = Mongoid::Clients.default
  current_db = client.database
  admin_db = Mongo::Database.new(client, Mongo::Database::ADMIN, current_db.options)
  admin_db.command(renameCollection: "#{current_db.name}.#{old_name}",
                   to: "#{current_db.name}.#{new_name}",
                   dropTarget: drop_target)
end

alexellis

Convert sequence of JPEG images to MP4 video

ffmpeg -r 24 -pattern_type glob -i '*.JPG' -i DSC_%04d.JPG -s hd1080 -vcodec libx264 timelapse.mp4

• -r 24 - output frame rate
• -pattern_type glob -i '*.JPG' - all JPG files in the current directory
• -i DSC_%04d.JPG - e.g. DSC_0397.JPG
• -s hd1080 - 1920x1080 resolution

Slower, better quality

rmm5t

Fast/efficient approach:

-- execute("UPDATE posts SET comments_count = (SELECT count(1) FROM comments WHERE comments.post_id = posts.id)")
   -> 1.3197s

Slow/naïve approach:

colby

alias speed="wget --output-document=/dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip"
alias wanip="curl http://ifconfig.co"

function ipinfo() { curl "http://ipinfo.io/$1"; }

awidegreen

Introduction

• C-a == Ctrl-a
• M-a == Alt-a

General

:q        close
:w        write/saves
:wa[!]    write/save all windows [force]
:wq       write/save and close

MohamedAlaa

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

IanVaughan

#!/usr/bin/env bash

uninstall() {
  list=`gem list --no-versions`
  for gem in $list; do
    gem uninstall $gem -aIx
  done
  gem list
  gem install bundler
}