- Be consistent with POSIX tools.
- CLI success comes from ease and predictability of use so be consistent.
- Support Piping and output direction to chain commands together.
- Work with GREP, AWK, JQ and other common tools and commands.
- Support productivity features like tab completion and parameter value completion.
- Commands should follow a "[noun] [noun] [verb]" pattern.
- For nouns that only support a single verb, the command should be named as a single hyphenated verb-noun pair.
- Commands should support all output types (be consistent).
- Exceptions are okay if only a 'raw' format makes sense e.g. XML.
- Commands and arguments should have descriptions.
- Include examples for the less straightforward commands.
- Commands should return an object or dictionary, not strings/bools/etc.;
logging.info(“Upload of myfile.txt successful”)NOTreturn “Upload successful”
- Log to ERROR or WARNING for user messages; don't use
print()function (by default it goes to STDOUT). - STDOUT vs. STDERR: STDOUT is used for actual command output. Everything else to STDERR (e.g. log/status/error messages).
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CLI - Provides the entry point.
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Commands - Provides logic to register and load commands.
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Arguments - Provides logic to register and load command arguments.
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Validators - Provides logic to valid or transform command arguments.
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Events - Provides an extensible events module that you can hook into.
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Config - Provides user-configurable options back by environment variables or config files.
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Logging - Provides consistent logging.
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Completion - Provides tab completion support.
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Prompting - Provides a consistent user-prompting experience.
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Help - Provides command/argument help.
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Output - Provides output options and displays command output.
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Query - Provides JMESPath query support.
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Testing - Provides a framework to test your commands.