Recursively create directories for all letters - bash

Question

I would like to create a folder structure based on a brace expansion such as {a-z}. Each string generated by the brace-expansion should be a new folder. Furthermore, each of these folders should contain the same set of subfolders similarly generated. And this up to a given level.
An example for the range a-z and depth 16
a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/
a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/b/
a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/c/
...
d/a/h/r/y/d/s/b/e/y/k/f/o/o/q/c/
...
z/z/z/z/z/z/z/z/z/z/z/z/z/z/z/y/
z/z/z/z/z/z/z/z/z/z/z/z/z/z/z/z/
The following code allows me to go upto depth 2:
for x in {a..z} ; do mkdir -p $x/{a..z} ; done
But how do I go further?

Answer 1

A recursive solution. Job is called with 2 params: max_depth and base_path
#!/bin/bash
function job()
{
local depth=$(($1-1))
local path=$2
local x
for x in a b c # reduced for test
do
mkdir -p "$path/$x"
((depth>0)) && job $depth "$path/$x"
done
}
job 3 ./test
Proof it with:
find test -type d

Answer 2

The simplest form would be to use any of the following lines:
mkdir -p {a..c}/{a..c} # depth 2
mkdir -p {a..c}/{a..c}/{a..c} # depth 3
mkdir -p {a..c}/{a..c}/{a..c}/{a..c} # depth 4
...
The brace-expansion will make all combinations and mkdir -p will take care of the rest.
Of course, you do not want to type this over and over for various sets. So you could generate the full brace-expansion-string with bash and use exec to process the brace-expansion-string before passing it to mkdir -p:
depth=3
set={a..c}
dirs=$(printf "/${set}%.0s" $(seq $depth))
mkdir -p $(eval echo .${dirs})
Be aware however that if your set has length m, and you want a depth of n, you are creating m^n directories. This number could conflict with the number of arguments you can pass on to a program.
Related information:
What is the maximum allowed depth of sub-folders?
https://www.in-ulm.de/~mascheck/various/argmax/

Answer 3

A recursive funcion may solve your problem. Take care with inodes generation when using high directory levels...
#!/bin/bash
function createDir {
mkdir -p $1 && cd $1;
for x in {a..z} ; do
local i=$(($2-1))
[ $i -lt 0 ] && continue;
createDir $x $i
done
cd ..
}
createDir $1 $2
Save into a file, like mkdir.sh, and call it: ./mkdir.sh <main_folder> <level>.