github.com/urfave/cli

Building CLI apps with urfave/cli feels natural once you understand the basic pattern. The flag handling is intuitive - you define flags directly on commands, and the framework handles parsing and validation automatically. Error messages when flags are missing or malformed are clear enough to fix issues quickly. The Action function pattern keeps your code organized, and subcommands compose well for complex CLIs.

The biggest pain point is the v1/v2 split. Many examples and Stack Overflow answers reference v2 (github.com/urfave/cli/v2), but if you're using v1, the API differences can trip you up. Context handling changed significantly between versions. Documentation exists but feels scattered - the README has examples, but finding patterns for middleware-like functionality or complex flag dependencies requires digging through issues.

Day-to-day, it's productive. Common tasks like environment variable fallbacks, required flags, and help text generation work smoothly. The framework stays out of your way until you need advanced features, where documentation becomes thinner. Community support is decent - GitHub issues get responses, though not always quickly.

I've used urfave/cli extensively for building command-line tools and it delivers a straightforward API with minimal dependencies—a significant plus from a supply chain perspective. The framework itself has zero external dependencies beyond the Go standard library, which drastically reduces attack surface. Flag parsing is predictable and input handling is relatively safe by default, though you still need to validate user inputs yourself as the library doesn't sanitize or escape arguments.

From a security standpoint, error handling is one area requiring attention. Default error messages can be verbose and may leak internal path information or command structure details if you're not careful about wrapping errors before display. The library doesn't do authentication or authorization—it's purely a CLI parser—so you need to implement those yourself for sensitive operations. The maintainers respond reasonably to security issues, though the v1 branch is in maintenance mode.

The library follows secure-by-default principles in that it doesn't introduce crypto weaknesses or network operations, but it won't protect you from writing insecure command handlers. Input validation is your responsibility.

The urfave/cli v1 package gets the job done for basic CLI applications, but working with it daily reveals friction points that stem from its age. The API works primarily through struct tags and global state patterns that feel dated compared to modern Go idioms. Flag definitions are verbose, requiring separate declaration and registration steps that make refactoring tedious.

Error messages are functional but bare-bones - you'll often find yourself wrapping errors to provide better context to users. The documentation covers basics adequately but lacks depth on common patterns like subcommand composition or custom flag types. IDE support is acceptable since it's all struct-based, but you lose type safety in several places where interface{} is used.

The real issue is that v2 exists and is significantly better, yet v1 continues to be maintained separately. This creates an awkward situation where you're using a legacy API that won't see modern improvements. Migration to v2 requires non-trivial rewrites due to API changes.