CLI Design Opinions

A penny for your thoughts…

Options over arguments

Positional arguments should be used sparingly, and if used should be required:

• The more positional arguments there are, the more confusing the CLI invocation becomes to read. (This is true of Python too.)

• Making some arguments optional, or arbitrary length, can make it harder to reason about. The parser handles this consistently by filling left to right, with an error if there is a non-optional unfilled after that. But that’s not obvious to a user just looking at a command line.

• A command should be doing one thing, and the arguments should be related directly to that.

  • A group, where the argument is the sub-command name.

  • A command acts on some files.

  • A command looks at a source and acts on a destination.