sh function for "tree" command

# Add this to your .bashrc or .zshrc or wherever
# Copyright (C) 2012 by Adam Katz <http://www.khopis.com/scripts>, GPLv3+
# see also http://www.commandlinefu.com/commands/view/10592/
function tree() {
  local dirs_only=''
  case $1 in
    -d )   dirs_only="-type d"; shift ;;
    -?* )  [ ! -r "$1" ] && echo "Usage: tree [-d] [PATH...]" && return 1 ;;
  esac
  find "${@:-.}" $dirs_only |sed 's:[^-][^/]*/:--:g; s/^-/ |/'
}