#!/bin/bash

set -e
set -u
set -o pipefail

# both GNU screen and tmux by default set TERM to screen or screen-256color
case "${TERM}" in
  screen*)
    exit 0
  ;;
esac

# GNU screen
if [[ -n "${STY:-}" ]]; then
  exit 0
elif [[ -n "${TMUX:-}" ]]; then
  exit 0
fi

# neither GNU screen nor tmux present
echo "Error: no terminal multiplexer (screen/tmux) detected." >&2
echo "Always execute this tool under GNU screen or tmux." >&2

exit 1
