QLTextFiles.sh

#!/bin/bash

curl -O https://github.com/whomwah/qlstephen/releases/download/1.4.2/QLStephen.qlgenerator.1.4.2.zip
unzip QLStephen.qlgenerator.1.4.2.zip

echo "Please enter your password when asked (the one sudo asks you for usuqlly). It's needed to copy some files to /Library/QuickLook"
sudo mv -f QLStephen.qlgenerator /Library/QuickLook
rm QLStephen.qlgenerator.1.4.2.zip
qlmanage -r

# enables text selection
defaults write com.apple.finder QLEnableTextSelection -bool true; killall Finder

echo "We're done. Have fun and do not forget to give a credit to QLStephen's author Duncan@https://github.com/whomwah"

Usage
curl https://gist.githubusercontent.com/blvz/4bb412b6828277e7982a/raw/b1694ccdeb89ef1fe34ecb7b6376a340191a4a25/QLTextFiles.sh | sh