The watch command is useful when you want your book to be rendered on every file change. You could repeatedly issue mdbook build every time a file is changed. But using mdbook watch once will watch your files and will trigger a build automatically whenever you modify a file.

Like init and build, watch can take a directory as argument to use instead of the current working directory.

mdbook watch path/to/book

When you use the --open (-o) option, mdbook will open the rendered book in your default web browser.

The --dest-dir (-d) option allows you to change the output directory for your book.

note: the watch command has not gotten a lot of testing yet, there could be some rough edges. If you discover a problem, please report it on Github