Mastering Bash

The double asterisk (**)

The double asterisk is being used in two different contexts:

• It is used as a exponentiation operator in an arithmetic context
• It is used as an extended file match globbing operator from Bash 4, meaning it matches filenames and directories recursively

So, we have this:

zarrelli:~$ for i in * ; do echo "$i" ; donefiletest2

This is different from the following:

zarrelli:~$ for i in ** ; do echo "$i" ; donefiletest2test2/file2

The double star matched all files and directories globally. If the double star does not work for you, enable the globstar shell options with zarrelli:~$ shopt -s globstar ; for i in ** ; do echo "$i" ; done. The globstar value changes the way the shell interprets the double star, which, in a file ...