#!/bin/bash
#####################################################
# Unix/Linux Folder Tree v2.9                       #
#                                                   #
# Displays structure of folder hierarchy            #
# ------------------------------------------------- #
# This tiny script uses "ls", "grep", and "sed"     #
# in a single command to show the nesting of        #
# subfolders.                                       #
#                                                   #
# Setup:                                            #
#    $ mkdir -p ~/apps/tree                         #
#    Save "tree.sh" into the "~/apps/tree" folder   #
#    $ cd ~/apps/tree                               #
#    $ chmod +x tree.sh                             #
#    $ ln -s tree.sh /usr/local/bin/tree            #
#    $ which tree                                   #
#                                                   #
# Usage:                                            #
#    $ tree [FOLDER]                                #
#                                                   #
# Examples:                                         #
#    $ tree                                         #
#    $ tree /usr/local/etc                          #
#    $ tree ..                                      #
#                                                   #
# WTFPL ~ https://centerkey.com/tree ~ Dem Pilafian #
#####################################################

echo
test -n "$1" && cd "$1"  #if parameter exists, use as base folder
pwd
ls -R | grep "^[.]/" | sed -e "s/:$//" -e "s/[^\/]*\//--/g" -e "s/^/   |/"
# Transformations:
#     grep    --> select folders (filter out files)
#     1st sed --> remove trailing colon
#     2nd sed --> replace higher level folder names with dashes
#     3rd sed --> indent graph and add leading vertical bar
topFolders=$(ls -F -1 | grep "/" | wc -l)
test $topFolders -ne 0 || echo "   --> no subfolders"
echo