The watch command
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.
Specify a directory
The watch command can take a directory as an argument to use as the book's
root instead of the current working directory.
mdbook watch path/to/book
--open
When you use the --open (-o) option, mdbook will open the rendered book in
your default web browser.
--dest-dir
The --dest-dir (-d) option allows you to change the output directory for the
book. Relative paths are interpreted relative to the book's root directory. If
not specified it will default to the value of the build.build-dir key in
book.toml, or to ./book.