Run rubocop against your current branch

$ git diff develop feature/one-signal --diff-filter=M --name-only -- *.rb | egrep -v 'db|config|spec' | xargs rubocop


Use `host` to get more information about domains

You might be using dig to find out A/CNAME/MX etc records of a domain from DNS servers. But if you just want to get a quick overview, use host:

$ host has address has address has address mail is handled by 1 mail is handled by 5 mail is handled by 5 mail is handled by 10 mail is handled by 10


Attaching file to ActiveStorage without HTTP

If you want to attach a file you generated on disk or downloaded from a user-submitted URL, you can do it like this.

  filename: 'file.pdf',
  # content type is optional
  content_type: 'application/pdf'


How to save a file with sudo in VIM

:w !sudo tee %


Zsh function to list file tree

Add this to your .zshrc

lst() {
    if [ "$1" != "" ] # or better, if [ -n "$1" ]
        ls -R $1 | grep ":$" | sed -e 's/:$//' -e 's/[^-][^\/]*\//--/g' -e 's/^/   /' -e 's/-/|/'
        ls -R | grep ":$" | sed -e 's/:$//' -e 's/[^-][^\/]*\//--/g' -e 's/^/   /' -e 's/-/|/'

Then you can run

$ lst spec

It should list all sub directory in spec folder in tree format.

You could change spec to any path you want.

or just use tree



Change system names on macOS

From term (or equivalent), copy and paste:

To change your public Host Name (i.e., 
sudo scutil --set HostName "New Name" 

To change your local Host Name (i.e., jeff.local): 
sudo scutil --set LocalHostName "New Name"

To change your Finder Computer Name (i.e., Jeff's MBP): 
sudo scutil --set ComputerName "New Name"

Finally, flush your DNS cache to force refresh: 
dscacheutil -flushcache 


Create your own git commands (aliases)

Ever wanted to shorten a git command? You can go with shell alilas for sure but you have to always include context so that you don't forget what each ailas stands for but you can define your own commands in git using aliases.

git config --global alias.  

For example; I'm too lazy to type git status so I want to shorten this to git s

git config --global alias.s status

And here we go now you can just type git s and get the status of current repository.


Amazon AWS S3 CLI copy with set perms

Open term (or equivalent) and paste the following:

S3 copy

  • to upload a world-readable file:
aws s3 cp source.file s3://bucket/path/dest.file --acl public-read

Options for --acl parameters are:

  • private - visibility to owner only
  • public-read - readable by all
  • public-read-write - readable and writable by all

Add new types to Rails 5 attributes API

The Rails 5 attributes API allows us to build form objects very easily.

I had previously been using an after_initialize callback to downcase emails, with the following code I can define an :email date type and values are automatically cast when set.

This has the advantage of casting subsequent calls to set the email value.

class EmailType < ActiveModel::Type::String
  def cast(value)
    return super unless value.is_a?(String)

ActiveModel::Type.register(:email, EmailType)

class Foo
  include ActiveModel::Model
  include ActiveModel::Attributes

  attribute :email, :email

> '').email
=> ''


Use FFmpeg and Apple Script to compress videos

Build an application you can drag-and-drop videos onto to compress them significantely:

Make sure you have ffmpeg installed (brew install ffmpeg).

Create a new Apple Script app: AppleScript on open filelist repeat with i in filelist tell application "Terminal" do script "ffmpeg -i " & POSIX path of i & " -vcodec h264 -acodec mp2 " & POSIX path of i & "_compressed.mp4" end tell end repeat end open