playing music on hold when launching a bash command

 This works using MacOS afplay

!/bin/bash

moh_file=~/Downloads/moh.mp3

afplay $moh_file &

pid=$!

trap "kill $pid" 2

while read line; do echo -e $line; done

kill $pid

Usage:
$ long-running-command [args] | moh_player

If you want to retain colours, run it through script:
$ script -q /dev/null long-running-command [args] | moh_player

Ubuntu dev machine space management

Visualize filesystems usage:

df -h

Show disk usage of un/hidden folders

 du -sch .[!.]* * |sort -h

Find working kernel

uname -r

List installed kernels

dpkg --list | grep linux-image 

Sort and display packages size:

dpkg-query -Wf '${Installed-Size}\t${Package}\n' | sort -n

Completely delete a package

sudo apt-get purge packagename

Delete unused packages

sudo apt-get autoremove

Clean Apt cache

sudo apt-get clean

Brew cache cleanup

rm -rf $(brew --cache)

Brew uninstall

sudo ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"

RVM

rvm uninstall ruby-2.3.3

Uninstall gems

gem uninstall -aIx

NPM cache cleanup

npm cache clean

Yarn (Node.js) cache cleanup

yarn cache clean