Reading files is no big deal with bash: you just redirect the input
to the script or pipe the output of another command into the script,
or you could do it inside the script if the file names are pre-determined.
You could also use process substitution to pass in the open
files (command pipelines actually) from the command line.
Another option, the one I describe here, is to just open the files
and read (or write) them as you like, as you'd do in other programming languages.