chruby for PostgreSQL

chpg.rb

require "formula"

class Chpg < Formula
  desc "PostgreSQL environment tool"
  homepage "https://gist.github.com/jasonmp85/218f3bba809ec086343a"
  url "https://gist.githubusercontent.com/jasonmp85/218f3bba809ec086343a/raw/db7e002ba593512b3a9ae27eb52762d104dae416/chpg.sh"
  sha256 "4a3d5165364e3f8289613dfe37d8e2a7615116b8a09c6a940c3207fe30e30d76"
  version "0.1.1"

  depends_on "petere/postgresql/postgresql-common"

  def install
    share.install "chpg.sh"
  end

  def caveats; <<~EOS
    Add the following to your ~/.bashrc or ~/.zshrc file:
      source #{opt_share}/chpg.sh
    EOS
  end
end

chpg.sh

CHPG_VERSION="0.1.1"

function chpg_reset()
{
	[[ -z "$PGCLUSTER" ]] && return

	unset PGCLUSTER PGHOST PGPORT
}

function chpg_use()
{
	[[ -n "$PGCLUSTER" ]] && chpg_reset

	pghost=`pg_conftool $1 $2 show -s unix_socket_directories | tr -d "'"`
	pgport=`pg_conftool $1 $2 show -s port`

	export PGCLUSTER="$1/$2"
	export PGHOST="${pghost}"
	export PGPORT="${pgport}"
}

function chpg()
{
	CLUSTERS=(`pg_lsclusters -h | awk '{print $1"/"$2}'`)

	case "$1" in
		-h|--help)
			echo "usage: chpg [cluster-version cluster-name | system]"
			;;
		-V|--version)
			echo "chpg: $CHPG_VERSION"
			;;
		"")
			local cluster star
			for cluster in "${CLUSTERS[@]}"; do
				if [[ "$cluster" == "$PGCLUSTER" ]]; then star="*"
				else																			star=" "
				fi

				echo " $star $cluster"
			done
			;;
		system) chpg_reset ;;
		*)
			local cluster match
			for cluster in "${CLUSTERS[@]}"; do
				case "${cluster}" in
					"$1/$2")	match="$cluster" && break ;;
				esac
			done

			if [[ -z "$match" ]]; then
				echo "chpg: unknown PostgreSQL cluster: $1/$2" >&2
				return 1
			fi

			chpg_use $*
			;;
	esac
}

Shamelessly copied from chruby.