how to write a script that takes any file as an input? (Newbie)

[webdev]

Hi I wrote a script for class that took one specific file as an input. Ideally, it should be able to take any file as an input. How do I do that? Someone suggested using $@ since is a global variable but I'm kinda confused on how to implement it. I'm thinking... $@=$1 $1=filename.txt then...