Suppose we have a list of files stored in a text file and we want to perform an operation on each of them within a bash script. How would we go about doing that? Well, there are several options, here are a few.

$ cat input-files.txt file-1.txt file-2.txt file-3.txt file-4.txt file-5.txt file-6.txt file-7.txt file-8.txt file-9.txt

There are various tools built into bash that enable you to manipulate a variable or string which come in handy when writing shell scripts. Here are a few notable ones:

Find the length of a string

${#string}

Get a Substring from a String

${string:pos} or ${string:pos:len}

Removing Substrings from a String

${string#substr} ${string%substr} ${string##substr} ${string%%substr}