正则表达式只通过提取前5个字符批量重命名for循环中的文件

I have many .xlsx files that look like XXX-A_2016(Final).xlsx and I am trying to write a shell script (bash) that will batch convert each one to csv, but also rename the output file to just "XXX-A.csv", so I think I need a regular expression within my for loop that extracts the first 5 characters of the input string (filename). I have xlsx2csv and I am using the following loop:I have many .xlsx files that look like XXX-A_20