Node js module that copy a file asyncrhonously using streams and calls a _callback_ when it finishes.

cp.js

var fs = require("fs"),
    util = require('util');

// Copy a file asyncrhonously using streams and calls a _callback_ when it
// finishes. 
exports.cp = (function() {
    return function (src, dst, cback, o) {
        // Options can have:
        //
        // * **force**: (*bool*) wich determines if files are being overriten.
        o = o || {};
        // Check if destination file exists
        fs.stat(dst, function (err) {
            // If file exists shows error unless _force_ is true.
            if ((!err) && !o.force) return cback(new Error(dst+" exists."));
            // If not exists or _force_ is true copy files using streams.
            fs.stat(src, function (err) {
                if (err) return cback(err);
                util.pump(fs.createReadStream(src),
                          fs.createWriteStream(dst),
                          cback);
            });
        });
    };
})();