gistfile1.txt

#!/bin/bash

# https://stackoverflow.com/a/13401143/465183

# Decimal ASCII codes (see man ascii)
ARR=( {48..57} {65..90} {97..122} )

# Array count
arrcount=${#ARR[@]}

# return a random string
get_rand_dir(){
    for ((i=1; i<$((RANDOM%30)); i++)) {
        printf \\$(printf '%03o' ${ARR[RANDOM%arrcount]});
    }
}

dir=/tmp/rand_dirs/

# appending random characters to make a hierarchy
for ((i=0; i<$((RANDOM%100)); i++)) {
    dir+="$(get_rand_dir)/"
}

echo "$dir"
mkdir -p "$dir"
cd "$dir"

while [[ $dir ]]; do
    dir=${dir%/*}
    cd $dir
    for ((i=0; i<$((RANDOM%100)); i++)) {
        mkdir &>/dev/null -p /tmp/rand_dirs/$(get_rand_dir)
    }
done

tree /tmp/rand_dirs