Is it possible to iterate through every word in stdin through means of Javascript?

Question

I need to know if it's possible to iterate through every word input through stdin into a program using JavaScript. If so, may I get any leads on how to do so?

Answer 1

With Node:

var stdin = process.openStdin();
var buf = '';

stdin.on('data', function(d) {
    buf += d.toString(); // when data is received on stdin, stash it in a string buffer
                         // call toString because d is actually a Buffer (raw bytes)
    pump(); // then process the buffer
});

function pump() {
    var pos;

    while ((pos = buf.indexOf(' ')) >= 0) { // keep going while there's a space somewhere in the buffer
        if (pos == 0) { // if there's more than one space in a row, the buffer will now start with a space
            buf = buf.slice(1); // discard it
            continue; // so that the next iteration will start with data
        }
        word(buf.slice(0,pos)); // hand off the word
        buf = buf.slice(pos+1); // and slice the processed data off the buffer
    }
}

function word(w) { // here's where we do something with a word
    console.log(w);
}

Processing stdin is much more complicated than a simple string split because Node presents stdin as a Stream (which emits chunks of incoming data as Buffers), not as a string. (It does the same thing with network streams and file I/O.)

This is a good thing because stdin can be arbitrarily large. Consider what would happen if you piped a multi-gigabyte file into your script. If it loaded stdin into a string first, it would first take a long time, then crash when you run out of RAM (specifically, process address space).

By handling stdin as a stream, you're able to handle arbitrarily large input with good performance, since your script only deals with small chunks of data at a time. The downside is obviously increased complexity.

The above code will work on any size input and doesn't break if a word gets chopped in half between chunks.

Answer 2

Assuming you're using an environment that has console.log and standard input is a string, then you can do this.

Input:

var stdin = "I hate to write more than enough.";

stdin.split(/\s/g).forEach(function(word){
    console.log(word)
});

Outputs:

I
hate
to
write
more
than
enough.