Though, you still should provide a way to read from file/write into file. I prefer passing "-" or /dev/stdin (/dev/stdout) for that purpose.
Just for the sake of debuggability, if someone would like to debug your script with a debugger/debug prints/debug reads
Why not both? Many of my favorite utilities are stdin/out by default, have file parameters, and will accept '-' to go back to stdin/out.
This is highly useful if you want to allow composition into scripts without forcing users to dynamically build parameters. Meaning, they can use, e.g. `FILE_NAME=${FILE_NAME:-"-"}; some-util --output $FILE_NAME;` and not have to decide whether or not to use the --output parameter in their script.
