Shell script that reproduced the tree command

tree.sh

#!/usr/bin/env bash
# treeを擬似的に再現したスクリプト

dir_count=0
file_count=0

traverse() {
  dir_count=$(expr $dir_count + 1)
  local directory=$1
  local prefix=$2

  local children=($(ls $directory))
  local child_count=${#children[@]}

  for idx in "${!children[@]}"; do 
    local child="${children[$idx]}"
    local child_prefix="│   "
    local pointer="├── "

    if [ $idx -eq $(expr ${#children[@]} - 1) ]; then
      pointer="└── "
      child_prefix="    "
    fi

    echo "${prefix}${pointer}$child"
    [ -d "$directory/$child" ] &&
      traverse "$directory/$child" "${prefix}$child_prefix" ||
      file_count=$(expr $file_count + 1)
  done
}

root="."
[ "$#" -ne 0 ] && root="$1"
echo $root

traverse $root ""
echo
echo "$(expr $dir_count - 1) directories, $file_count files"

The output doesn't handle singular and plural cases as the actual tree command does.

You should replace (expr...)with(( ... )). expr will launch a new process, while $(( )) is a bash internal.

For the same reason, and to handle filenames with spaces, you should replace ($(ls $directory)) with ("$directory"/*). Then you'll have to cut out the directory name.

Here is the result :

 ...

Thanks a lot, @Vouze! Just updated this script to show trailing backslash for folders, not to print strange tail if the directory is empty, and colored folders and executable files in the tree:

#!/usr/bin/env bash

dir_count=0
file_count=0

traverse() {
  dir_count=$((dir_count + 1))
  local directory=$1
  local prefix=$2

  local children=("$directory"/*)
  local child_count=${#children[@]}

  for idx in "${!children[@]}"
  do local child="${children[$idx]}"
    child=${child##*/}
    local child_prefix="│   "
    local pointer="├── "

    if [ $idx -eq $(( ${#children[@]} - 1)) ]; then
      pointer="└── "
      child_prefix="    "
    fi

    if [ -e $directory/$child ]; then
      if [ -d "$directory/$child" ]; then
        echo -e "${prefix}${pointer}\033[1;34m$child/\033[0m"
        traverse "$directory/$child" "$prefix$child_prefix"
      else
        if [ -x $directory/$child ]; then
          echo -e "${prefix}${pointer}\033[0;32m$child\033[0m"
        else
          echo "${prefix}${pointer}$child"
        fi
        file_count=$((file_count + 1))
      fi
    fi

  done
}

root="."
[ "$#" -ne 0 ] && root="$1"
echo $root

traverse $root ""
echo
echo "$((dir_count - 1)) directories, $file_count files"