${##%%} in the shell stands for what, memo

#!/bin/bash

A=aigo.goto.aigo.goto

Echo ${a#*go}

Echo ${a##*go}

Echo ${a%.*}

Echo ${a%%go*}

Execution results

. Goto.aigo.goto

To

Aigo.goto.aigo

Ai

The memo is as follows:

#* string--from left to right the first occurrence of the "string" in variable a (most left) and everything on its left is removed (because there is a *)

##* string--from left to right, remove the last occurrence of "string" from the variable A (right) and everything on its left

The% string *--from right to left removes the first "string" (right) from the variable A and everything on its right.

The *--string is removed from right to left with the last string in the variable a (left) and everything on its right.

${##%%} in the shell stands for what, memo