In the gulpfile, we are performing the following instructions:

1. Import Gulp and Gulp-shell.
2. Create tasks with shell.task as the function to execute.
3. shell.task can execute a command-line instruction. Keep your shell commands inside that function.
4. Add a watch task for watching source files. The task list will be executed when files are modified.
5. Create a default task for running. Add a watch to it.

Gulp is a great tool for these kinds of use cases. So, please go through the official documentation of Gulp at http://gulpjs.com/.