fs.read'ing a stream.fd

[Volkan Yazıcı]

Hi! I am having trouble while fs.read'ing from fd of a stream. For instance, below script produces no outputs. What am I missing?

var fs = require("fs"),
    s = fs.createReadStream(__filename),
    l = 8192,
    b = new Buffer(l);

s.on("open", function() {
        fs.read(s.fd, b, 0, l, function (err, nbytes) {
                console.log(
                        "err: " + err + ", " +
                        "nbytes: " + nbytes + ", " +
                        "buf: " + b.toString(0, nbytes));
        });
});

[Martin Cooper]

You're mixing up two different approaches to reading the file.

When you use fs.createReadStream(), the file will be read automatically as a stream, and you'll start seeing 'data' events with chunks of data as they're read. With this model, you don't do the reading, the stream does it for you.

On the other hand, if you want to read the file manually, you'll need to open it using fs.open() first. Then you can use fs.read() calls to get the data.

I'd recommend the stream approach, unless there's some reason you can't do that.

--
Martin Cooper

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[Volkan Yazıcı]

The problem is some libraries operate on fds to consume the input partially. (E.g., consider parsing the header of a binary file. Library first makes some read()'s, and by looking at the result of those read()'s, maybe some more read()'s too, etc.) OTOH, in my case, the input is piped through some other library which provides you a stream. And I need to pipe that stream to some other library that asks for a fd. Any recommendations?