How to use the command npx (with examples)

npx is a command-line tool that allows you to execute binaries from npm packages. It provides a convenient way to run executables without needing to install them globally or add them to your system’s PATH. This article will explore different use cases of the npx command and provide examples of how to use them.

Use case 1: Execute the command from a local or remote npm package

Code:

npx command argument1 argument2 ...

Motivation:

• This use case is useful when you want to execute a specific command from an npm package without installing it globally.
• It allows you to run the command without worrying about the package’s version or conflicts with other installed packages.

Explanation:

• npx: The npx command itself.
• command: The name of the command you want to execute.
• argument1 argument2 ...: Optional arguments that can be passed to the command.

Example output:

$ npx create-react-app my-app
...

In this example, the create-react-app command is executed using npx to create a new React application. The command is fetched from the create-react-app package in the npm registry and executed.

Use case 2: Explicitly specify the package when multiple commands with the same name exist

Code:

npx --package package command

Motivation:

• This use case is useful when there are multiple packages with commands of the same name installed in your local or global environment.
• It allows you to explicitly specify which package’s command you want to execute.

Explanation:

• npx: The npx command itself.
• --package package: The package name or path to the package’s directory.
• command: The name of the command you want to execute.

Example output:

$ npx --package my-package command
...

In this example, the command from the my-package npm package is executed using npx. It ensures that the command is fetched and executed from the specified package, regardless of any other packages with the same command name.

Use case 3: Run a command if it exists in the current path or in node_modules/.bin

Code:

npx --no-install command argument1 argument2 ...

Motivation:

• This use case is useful when you want to execute a command but only if it already exists in the current path or in the node_modules/.bin directory.
• It prevents unnecessary installation of the command if it is already available.

Explanation:

• npx: The npx command itself.
• --no-install: Prevents the command from being installed if it doesn’t already exist.
• command: The name of the command you want to execute.
• argument1 argument2 ...: Optional arguments that can be passed to the command.

Example output:

$ npx --no-install prettier --version
1.19.1

In this example, the prettier --version command is executed using npx. The --no-install flag ensures that npx only runs the command if prettier is already available in the current path or in the node_modules/.bin directory.

Use case 4: Execute a specific command suppressing any output from npx itself

Code:

npx --quiet command argument1 argument2 ...

Motivation:

• This use case is useful when you want to execute a command but suppress any output from npx itself.
• It allows you to focus on the output of the executed command without any additional noise.

Explanation:

• npx: The npx command itself.
• --quiet: Suppresses any output from npx itself.
• command: The name of the command you want to execute.
• argument1 argument2 ...: Optional arguments that can be passed to the command.

Example output:

$ npx --quiet jest
... (output from Jest command)

In this example, the jest command is executed using npx. The --quiet flag ensures that npx does not output its own information, and only the output from the executed jest command is shown.

Use case 5: Display help

Code:

npx --help

Motivation:

• This use case is useful when you want to quickly access the help information for npx.
• It provides a concise way to view the available options and flags for using npx.

Explanation:

• npx: The npx command itself.
• --help: Displays the help information for npx.

Example output:

$ npx --help
Usage: npx [options] <command>[@version] [command-arg]...

Execute binaries from packages installed in the current directory, eg. run eslint:
    $ npx eslint [args]

Options:
  -p, --package <pkg>    Specify a package version for the command
  -c, --call             Invokes "<command> -- <args...>".+...

This example shows the output of running npx --help. It displays the available options and usage examples for the npx command. This can be used as a quick reference to understand how to use npx effectively.

Conclusion:

npx is a powerful command-line tool that simplifies the execution of binaries from npm packages. It allows you to run commands from local or remote packages, specify packages explicitly, avoid unnecessary installations, suppress npx output, and access help information easily. By understanding these different use cases and their corresponding options and flags, you can make the most out of npx in your development workflow.