Clap

Clap is used to parse and validate the string of command line arguments provided by a user at runtime. You provide the list of valid possibilities, and clap handles the rest. This means you focus on your applications functionality, and less on the parsing and validating of arguments.

Clap provides many things 'for free' (with no configuration) including the traditional version and help switches (or flags) along with associated messages. If you are using subcommands, clap will also auto-generate a help subcommand and separate associated help messages.

Once clap parses the user provided string of arguments, it returns the matches along with any applicable values. If the user made an error or typo, it informs them with a friendly message and exits gracefully (or returns a Result type and allows you to perform any clean up prior to exit). Because of this, you can make reasonable assumptions in your code about the validity of the arguments prior to your applications main execution.