linux - What is the functionality of ## and %% in bash -

disk="/dev/sda" local dev_node=${disk##*/} 

dev_node assigned "sda".

also,

partition="/dev/sda3" echo ${partition%%[0-9]*} 

it returns /dev/sda , remove 3.

i did not understand functionality of ##*/ , %%[0-9]*in above commands. tried searching not enough information.

please explain , provide links tutorial related this.

this manual / tutorial. concerns question:

${string##substring} deletes longest match of $substring front of $string.

and

${string%%substring} deletes longest match of $substring back of $string.

applied example: removing longest substring matching */ /dev/sda results in sda