Does it save the whole file to RAM? about line-reader

[ungoldman]

It uses a read stream internally, and additionally buffers one line at a time using a separator character, if I'm reading the source correctly. So only one line is buffered into memory at a time.

What makes streams unique, is that instead of a program reading a file into memory all at once like in the traditional way, streams read chunks of data piece by piece, processing its content without keeping it all in memory.

src: https://nodesource.com/blog/understanding-streams-in-nodejs/

ref: https://nodejs.org/api/fs.html#filehandlecreatereadstreamoptions