Grunt task for cycling through each item in a directory on an interval and creating a symlink which points to it. This is helpful for cycling through logs, or an archive of data captured over time. Coupled with a server, it serves as a good simulated data endpoint. This should be defined after grunt.initConfig inside your Gruntfile, or you can r…

example.txt

$ grunt link-cycler --root=archive/json --interval=30000 --link=current --verbose --initial=10

Running "link-cycler" task

Cycling through last 3 of 12 children, 1 per 30000ms...

Child 10/12:
Linking archive/json/current to archive/json/2013-09-23_12-28-32

Child 11/12:
Unlinking archive/json/current
Linking archive/json/current to archive/json/2013-09-23_12-58-32

Child 12/12:
Unlinking archive/json/current
Linking archive/json/current to archive/json/2013-09-23_13-28-32

Reached last child. Exiting.

Done, without errors.

link-cycler.js

grunt.registerTask('link-cycler', function () {
    var rootPath = grunt.option('root') || '.',
        linkName = grunt.option('link') || '.link-cycler-current-link',
        cycleInterval = +grunt.option('interval') || 1000,
        nextIndex = +(grunt.option('initial') || 1) - 1,
        linkPath = slashed(rootPath) + linkName,
        rootChildNames,
        done;

    function slashed(str) {
        return str + (str.charAt(str.length - 1) === '/' ? '' : '/');
    }

    function next() {
        var name = rootChildNames[nextIndex],
            path;

        if (!name) {
            grunt.verbose.writeln('\nReached last child. Exiting.');
            return done();
        }

        grunt.verbose.writeln('\nChild ' + (nextIndex + 1) + '/' + rootChildNames.length + ':');
        name = rootChildNames[nextIndex];
        path = slashed(rootPath) + name;
        nextIndex++;

        if (fs.existsSync(path)) {

            if (path !== linkPath) {

                if (fs.existsSync(linkPath)) {
                    grunt.verbose.writeln('Unlinking ' + linkPath);
                    fs.unlinkSync(linkPath);
                }

                grunt.verbose.writeln('Linking ' + linkPath + ' to ' + path);
                fs.symlinkSync(name, linkPath, fs.statSync(path).isDirectory() ? 'dir' : 'file');

                return setTimeout(next, cycleInterval);

            } else {

                grunt.verbose.writeln('Skipping existing link ' + linkPath);
                return next();

            }


        } else {

            grunt.verbose.writeln('Skipping non-existant path ' + path);
            return next();

        }
    }

    if (!fs.existsSync(rootPath)) {
        grunt.warn('\nRoot path does not exist. Exiting.');
    }

    done = this.async();

    rootChildNames = fs.readdirSync(rootPath).filter(function (name) { return name !== linkName; });

    grunt.log.writeln('\nCycling through ' + (nextIndex ? ('last ' + (rootChildNames.length - nextIndex) + ' of ') : '') + rootChildNames.length + ' children, 1 per ' + cycleInterval + 'ms...');
    next();

});