I want to Extract the date from this string in Bash and save it to a variable

I want to Extract the date from this string in Bash and save it to a variable
but the problem im facing is there are many – and I cant use ##

7_I-9112135749087-ZA_23-20211021-085359_2051521761_0000.zip

I want to extract 20211021 Please

Thanks

>Solution :

Assuming the filenames are always in the same format, you can do this in one of two ways.

Using just string manipulation:

$ file="7_I-9112135749087-ZA_23-20211021-085359_2051521761_0000.zip";

$ file=${file%-*};  # remove last dash through end of string
$ file=${file##*-}; # remove everything up to last remaining dash

$ echo "$file";
20211021

Using an array:

$ file="7_I-9112135749087-ZA_23-20211021-085359_2051521761_0000.zip";
$ IFS="-" read -ra parts <<< "$file";  # split into 0-based array using "-" as delimiter
$ echo ${parts[3]}; # 4th index
20211021