I have a bunch of files which are named: mem0.csv mem1.csv . . . . mem153.csv . . . They are all in the same folder. When I do ls in the folder they appear in an order of mem0.csv mem1.csv mem10.csv mem100.csv . . . mem2.csv mem20.csv . . . I want to create a bash script to push 0's between mem and the number. I figure that I need to add 0's until all the filenames are of the same length only problem is that I don't know how to do this.