TypeError: path must be a string with commander

Question

I want to read a file with commander:

#!/usr/bin/env node

var fs = require('fs')
var program = require('commander')

program
  .version('0.0.1')
  .usage('<keywords>')
  .parse(process.argv)

if(!program.args.length) {
  program.help()
} else {
  var filename = program.args

  console.log('keys: ' + filename)

  fs.readFile(filename, 'utf8', function(err, data) {
    if (err) throw err
    console.log(data)
  })
}

$ ./m2k.js test.txt

However, I get the this error:

fs.js:430
  binding.open(pathModule._makeLong(path),
          ^
TypeError: path must be a string

What am I doing wrong?

(I have a file called test.txt in the same folder as m2k.js.)

Answer 1

If you print the type of program.args or the program.args itself, you will know that its an Array.

console.log(Object.prototype.toString.call(program.args), program.args);
// [object Array] [ 'test.txt' ]

So, you need to use the correct index to be used like this

var filename = program.args[0];

I think the result of console.log('keys: ' + filename) is not helping you much. It is because when you use + operator, it will try to convert the filename object to a string and the String array converted to a string normally just has comma separated strings. You can check that like this

console.log(['a'].toString(), ['a', 'b'].toString());
// a a,b