Globstar

Standard star

The standard star gives files and directory at the current level.

for f in *; do
    echo $f
done

Using ls, you can see files in each top-level directory.

ls *

You use this go show output recursively.

ls -R

But this is not recommended for rename, deleting, etc. And you should not be parsing the output of ls.

What is globstar

To find files recursively, use the globstar symbol - **. This must be enabled.

From Bash 4 docs:

globstar
    If set, the pattern ** used in a pathname expansion context will
    match all files and zero or more directories and subdirectories.
    If the pattern is followed by a /, only directories and
    subdirectories match.

Set option

Do this once off or in your shell config file.

Bash

Check if it is enabled.

shopt globstar

Enable.

shopt -s globstar

In scripting, check with shopt -q globstar. Copied solution below - untested.

if shopt -q globstar; then
  ...
if

ZSH

Globstar is enabled already - recommended to use this. Note ** is not sufficient.

**/*

One piece of advice said to do this, but this works with #, ^ and ~ according to docs.

setopt extended_glob

Example use

ls **

ls **/*.py

ls -1 **/*.(sh|py)