https://tech.goyun.info/2020/12/how-to-extract-filename-and-extension.html

How to extract filename and extension in bash shell script.sh

#!/bin/bash
# get file name only without path
file_name=$(basename $BASH_SOURCE)
# get extension
file_extension="${file_name##*.}"
# get file name without extension
file="${file_name%.*}"
# print them to verify
echo "Full input file : $BASH_SOURCE"
echo "Filename only : $file_name"
echo "File extension only: $file_extension"
echo "First part of filename only, without extension: $file"