commander.js simple use case: one single file argument

I've seen that most people use commander npm package when having to deal with command-line parsing. I would like to use it as well because it seems to have pretty advanced functionality (e.g. commands, help, option flags, etc).

However, for the first version of my program I don't need such advanced features, I just need commander to parse the arguments, and find a single filename provided (mandatory argument).

I've tried:

import commander = require("commander");

const cli =
  commander
    .version("1.0.0")
    .description("Foo bar baz")
    .usage('[options] <file>')
    .arguments('<file>')
    .action(function(file) {
        if (file == null) console.log("no file")
        else console.log("file was " + file);
    })
    .parse(process.argv);

However, with this:

• Nothing gets printed if I don't pass any argument, am I using the action() function properly or is my null check wrong? Ideally it should print the usage string I pass in this case, and finish with exitCode!=0?
• How can I detect if the user sent too many filenames (too many arguments) and give her an error?

It seems that action function won't be executed when no argument based on issue.

But you can check like

const cli = commander
    .version('0.1.0')
    .usage('[options] <file>')
    .arguments('<file>')
    .action(function(file) {
        fileValue = file;
    })
    .parse(process.argv);

if (typeof fileValue === 'undefined') {
    console.error('no file given!');
    process.exit(1);
}
console.log('file was ' + fileValue);