如何在bash中特定字符之间的字符串中添加字符？

Question

Right now I'm working on creating a script in linux bash shell that adds the word "-BACKUP" to a file name between certain points. For example, if I had a file/string called file1.txt I would want to add the "-BACKUP" between "file1" and ".txt" to make "file1-BACKUP.txt". How would I go about doing that? Would I use the basename command anywhere? In this situation, the extension and stem could be anything, not just what I gave as an example. All help is appreciated!

Answer 1

Use the substring processing parameter expansion operator % to remove the suffix from the string, then append the new text. The variable must be enclosed in braces for substring processing parameter expansion to work.

var="file1.txt"

echo "${var%.txt}.BACKUP.txt"