Cmdliner
A declarative library for defining command line interfaces in OCaml, handling parsing, help, and man pages.
What is Cmdliner?
Cmdliner is a library for OCaml that provides a declarative way to define command line interfaces. It converts command line arguments into OCaml values and passes them to functions, automatically handling parsing, help messages, and man page generation. It solves the problem of manually managing CLI complexity in OCaml applications.
OCaml developers building command-line tools or applications that require robust, standards-compliant argument parsing and interface management.
Developers choose Cmdliner for its declarative, compositional approach that reduces boilerplate, ensures compliance with POSIX/GNU conventions, and automatically handles error reporting, help, and documentation generation without external dependencies.
Overview
Declarative definition of command line interfaces for OCaml
Use Cases
Best For
- Building OCaml command-line tools with complex argument structures
- Creating multi-command CLI applications in OCaml
- Generating UNIX man pages automatically from OCaml code
- Ensuring POSIX and GNU compliance in OCaml CLI programs
- Simplifying CLI parsing and error handling in OCaml projects
- Developing self-documenting command-line interfaces in OCaml
Not Ideal For
- OCaml projects with only a few simple arguments where the standard library's Arg module suffices
- Teams building non-command-line applications like GUIs or web services in OCaml
- Developers needing advanced, non-standard CLI features beyond POSIX/GNU conventions
- Projects in programming languages other than OCaml
Pros & Cons
Pros
Uses a simple, compositional mechanism to define CLI interfaces declaratively, reducing boilerplate and errors, as stated in the README.
Manages syntax errors, help messages, and UNIX man page generation without manual intervention, saving development time.
Supports programs with single or multiple commands, accommodating complex CLI structures out of the box.
Respects most POSIX and GNU conventions, ensuring interoperability and user familiarity.
A self-contained library that simplifies integration and reduces project complexity, as highlighted in the features.
Cons
Exclusively for OCaml projects, making it irrelevant for developers using other programming languages.
The compositional, functional approach can be challenging for those accustomed to imperative parsing libraries, requiring a mindset shift.
The README notes it respects 'most' conventions, which may leave gaps for edge cases or advanced CLI features.
Documentation points to the OCaml forum for questions, indicating limited official support and reliance on community help.
Frequently Asked Questions
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