Get swift toolchain id from toolchain download name

get_swift_toolchain_id.sh

#!/usr/bin/env bash

readonly target_swift_toolchain_name='swift-4.1.3-RELEASE.xctoolchain'
readonly toolchain_plist_file_path="/Library/Developer/Toolchains/${target_swift_toolchain_name}/Info.plist"

if [ ! -f "${toolchain_plist_file_path}" ]; then
  echo
  echo "ERROR: no toolchain found at [${toolchain_plist_file_path}]"
  exit 1
fi

grep -A 1 'CFBundleIdentifier' "${toolchain_plist_file_path}" | tail -1 \
    | sed 's/\<string\>//' | sed 's/\<\/string\>//' \
    | grep -Eo '\S+'