Diff commands

diff -u <(./cmd1) <(./cmd2)

Find files without some content:
diff -u <(ag -l) <(ag -l content) | grep "^-\b"

To install ag:
https://github.com/ggreer/the_silver_searcher

Get the filepaths out of a diff:
ag '^\+\+\+' diff | cut -d' ' -f2 | sed -re 's,^b/,,'
ag '^\+\+\+' diff | cut -d' ' -f2 | sed -e 's,^b/,,' | sed -e '/\/dev\/null/d'

Alt-tab in KDE4

System Settings -> Desktop -> Desktop Effects -> All Effects -> Flip Switch (tick and apply)

Vim Tabular plugin

0. Links:
http://vimcasts.org/episodes/aligning-text-with-tabular-vim/
https://github.com/godlygeek/tabular
https://github.com/tpope/vim-pathogen

1. Install pathogen:
mkdir -p ~/.vim/autoload ~/.vim/bundle && \
curl -LSso ~/.vim/autoload/pathogen.vim https://tpo.pe/pathogen.vim

2. Configure pathogen:
vi .vimrc:
execute pathogen#infect()

Now any plugins you wish to install can be extracted to a subdirectory under ~/.vim/bundle, and they will be added to the 'runtimepath'. Observe:
cd ~/.vim/bundle && \
git clone git://github.com/tpope/vim-sensible.git

3. Install tabular:
cd ~/.vim/bundle
git clone git://github.com/godlygeek/tabular.git

4. Configure help:
vim
:Helptags

5. Read help:
vim
:help tabular

6. Use:
<select lines>
:Tab /=
:Tab /\.

X session

Start clean X session:
$ xinit /usr/bin/xterm -- :1

Keyboard keys

Extra keyboard keys
Console:
# showkey --keycodes

GUI:
$ xev | grep -A2 --line-buffered '^KeyRelease' | sed -n '/keycode /s/^.*keycode \([0-9]*\).* (.*, \(.*\)).*$/\1 \2/p'

Grub

vi /etc/default/grub

grub2-mkconfig -o /boot/grub2/grub.cfg