TIL, 2017-05-11

Philosophy, but when a class contains an instance of another class, don’t call that other class’s methods immediately, that way you can add methods to the child class which shouldn’t affect the implementation of the parent class.
| sed -n 2p to get output of line. So to get last commit, do git log -1 | sed -n 5p | pbcopy.
gem clipboard to copy Ruby pry or irb output to the system clipboard.
head - display first few lines of a file.
cat is viewing the command line output in totality, less is for viewing it in parts.
ag -l - view file names only of the ag output.
du -h - disk usage (human readable form).