See CLI in the Prettier docs.

Once installed, Prettier can be used as a CLI tool.

Usage

You might install it globally and use it as:

$ prettier .

Or you might install it in a project and set it up as an NPM script. So you can run it as:

$ npm run format

Help

$ prettier -h
Usage: prettier [options] [file/dir/glob ...]

By default, output is written to stdout.
Stdin is read if it is piped to Prettier and no files are given.

Output options:

  -c, --check              Check if the given files are formatted, print a human-friendly summary
                           message and paths to unformatted files (see also --list-different).
  -l, --list-different     Print the names of files that are different from Prettier's formatting (see also --check).
  -w, --write              Edit files in-place. (Beware!)
...

Examples

Be sure to use a path to a file or directory.

Default

The default behavior will print changes (possibly very long). Without saving changes.

$ prettier .

Check

Get a summary with --check. Again this doesn’t save changes.

$ prettier -c .
Checking formatting...
[warn] index.js
[warn] foo/bar.js
...
[warn] Code style issues found in the above file(s). Forgot to run Prettier?

This can be useful in a CI or git hooks flow, where you want to automate a check and abort if at least one file needs changing and a commit.

Edit

Format files and save changes.

$ prettier -w .

Flags

Complicated example:

$ prettier --single-quote \
  --trailing-comma all \
  --write docs \
  package.json \
  "{app,__{tests,mocks}__}/**/*.js"