Example gulp plugin

gulp-plugin.js

var gutil = require( 'gulp-util' );
var through  = require( 'through2' );
var path = require( 'path' );

module.exports = function () {
  var transform = function( file, enc, callback ) {
    var content = file.contents.toString();

    // Do something to content here

    var newfile = new gutil.File( {
      cwd: __dirname,
      path: path.join( __dirname, file.path ), // Do something if you need
      contents: new Buffer( JSON.stringify( content ) + "\n" )
    } );

    this.push( newfile );
    return callback();
  };

  return through.obj( transform );
};