Wanting a Unix alias that takes a command-line argument (shell script, actually)

I wanted to create a Unix alias that took an argument (command-line argument), but from what I saw, that wasn’t going to be easy, so I created this little shell script to do what I want. It fails gracefully if you don’t supply a command-line argument, and runs the desired command if you do supply it:

#!/bin/sh

# NAME:    scw
# VERSION: 0.1
# PURPOSE: a script that works like a Unix alias
#          that requires a command-line argument

filename=""
if [ $1 ]
then
    filename="$1"
else
    echo "PURPOSE: Run 'scala-cli <filename> --watch'"
    echo "USAGE:   scw <filename>"
    exit 1
fi

scala-cli $filename --watch

I keep a bin directory in my home directory, and it’s in my PATH, so I just drop this shell script in there and then I can use it like a Unix alias.

You can also use it as an example for any similar script you want to run, i.e., a simple shell script that handles a command-line argument.