Shell script for backing up the list of installed Homebrew (brew) packages

brewdump.sh

#!/bin/zsh -l
# This script can easily be added to your crontab for scheduled backups.
#
# EXITS
SUCCESS=0
BUNDLE_FAILED=1
BACKUP_FILE_EXISTS=2
MOVE_FAILED=3
NO_HOMEBREW=4

set HOMEBREW_PREFIX
BREW_ARM_PREFIX=/opt/homebrew
BREW_X86_PREFIX=/usr/local
BREWFILES=~/Brewfiles
ARCH=$(arch)

if [[ ${ARCH} == "arm64" ]]; then
	HOMEBREW_PREFIX="${BREW_ARM_PREFIX}"
else
	HOMEBREW_PREFIX="${BREW_X86_PREFIX}"
	BREWFILES=$BREWFILES-x86
fi

[ ! -d ${HOMEBREW_PREFIX} ] && exit $NO_HOMEBREW

BREWBIN="${HOMEBREW_PREFIX}/bin/brew"

cd ~

if [ ! -d $BREWFILES ]; then
	mkdir -p $BREWFILES
fi

if [ -f ~/.Brewfile ]; then
	echo ~/.Brewfile already exists. Remove this file and try again. >&2
	exit $BACKUP_FILE_EXISTS
fi

#Update everything
# ${BREWBIN} update > /dev/null 2>&1 && exit 5
$BREWBIN bundle dump --describe --global > /dev/null 2>&1

BREW_EXIT=$?

if [ "$BREW_EXIT" -ne "0" ]; then
	echo Brew bundle dump failed with return code: $BREW_EXIT >&2
	exit $BUNDLE_FAILED
fi

unset BREW_EXIT

DATE=$(date +"%Y%m%d-%H%M%S")

if [ -e ~/.Brewfile ]; then
	mv ~/.Brewfile $BREWFILES/Brewfile-${DATE}; 
	BREW_EXIT=$?
	if [ "$BREW_EXIT" -ne "0" ]; then
		echo The mv command failed with exit code: $BREW_EXIT >&2
		echo You should mv or rm ~/.Brewfile before running this script again. >&2
		exit $MOVE_FAILED
	fi;
fi; 

exit $SUCCESS