Install a previous version of a formula with Homebrew

brewv

#!/bin/bash
#
# Installs the previous version of a Homebrew formula
#
# Usage: brewv formula_name desired_version
#
# Based on http://stackoverflow.com/questions/3987683/homebrew-install-specific-version-of-formula#9832084
#
# Author:	Matti Schneider <[email protected]> (http://mattischneider.fr)

versions=$(brew versions $1)
result=$(echo "$versions" | grep -m 1 $2) #-m 1 to stop as soon as possible

if [[ $? = 0 ]]
then
	commit=$(echo $result | cut -d ' ' -f 4)
	formula=$(echo $result | cut -d ' ' -f 5)
	
	cd /usr/local
	if [[ -e $formula ]]
	then brew unlink $1	# will fail if not already installed, hence the check above
	fi
	git checkout $commit $formula &&
	brew install $1 &&
	git reset HEAD $formula &&
	git checkout -- $formula
	cd - > /dev/null
	echo "$1 $2 installed."
	echo "You can now switch versions with 'brew switch $1 <version>'"
else
	echo "$versions"
	echo
	echo "No version matching '$2' for '$1'"
	echo "Available versions have been printed above"
	exit 1
fi

This all doesn't seem to be working anymore.

What worked for me: run brew info python3 to see what other versions of python3 have been installed (3.5.2_3 was listed), and then brew switch python3 3.5.2_3 to switch to the old version, and brew pin python3 to prevent upgrading.

Not sure how this works if you've never had older versions installed...