node.js - fs.createReadStream(path[, options]) - What are those options? -

according node's v6.10.2 api - options object or string following defaults:

{ flags: 'r', encoding: null, fd: null, mode: 0o666, autoclose: true } 

but i've seen highwatermark property being used set buffer size. api didn't put on option. i'm wondering there more options api didn't write on document. if can find full option list?

and api didn't talk flags, know flags dose in case , what's difference between

flags: r flags: w flags: r+ 

i tried find answer didn't find helpful information. appreciate if me understand topic. thanks.