Stories with Tag getopt

• argp: GNU-style command line argument parser for Go

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  Posted: 2025-03-23 12:45:21

  Verbose tl;dr

  argp is a Go library providing a GNU-style command-line argument parser. It supports features like short and long options, flags, subcommands, required arguments, default values, and generating help text automatically. The library aims for flexibility and correctness while striving for good performance and minimal dependencies. It emphasizes handling POSIX-style argument conventions and provides a simple, declarative API for defining command-line interfaces within Go applications.

  The GitHub repository argp, created by Tom de Wolff, introduces a Go package that provides a command-line argument parser mimicking the style and functionality of GNU's argp library. This allows developers familiar with the GNU argument parsing conventions to easily implement similar behavior in their Go programs. The package aims to be a robust and feature-rich solution for handling command-line input.

  Key features of this Go implementation include support for both short and long options, with automatic generation of help text. It handles various argument types such as flags (boolean), options with associated values (strings, integers, etc.), positional arguments, and subcommands. The parser can be customized extensively to enforce required arguments, define default values, specify valid ranges for numeric arguments, and provide detailed usage instructions.

  The argp package uses a declarative approach, allowing developers to define the command-line interface through structs and struct tags. This approach promotes clarity and makes it easier to manage complex argument structures. Functions are provided to parse the command-line arguments and populate the corresponding struct fields. Error handling is integrated, providing informative messages to the user in case of invalid input.

  The package aims for high performance and strives to be a reliable and efficient solution for parsing command-line arguments in Go applications. The documentation within the repository provides detailed explanations and examples of usage, covering various scenarios and demonstrating how to leverage the package's capabilities. It also outlines how to handle different argument types, define subcommands, and customize the generated help text. The project maintains a focus on adhering to the established GNU argp conventions, ensuring a familiar experience for developers accustomed to that style of argument parsing.

  • Go
  • Golang
  • command-line
  • argument-parsing
  • cli
  • GNU
  • argp
  • parsing
  • Library
  • flag-parsing
  • getopt
  • command-line-interface
  • command-line-arguments
  • option-parsing

  Summary of Comments ( 18 )
  https://news.ycombinator.com/item?id=43452525

  Verbose tl;dr

  Hacker News users discussed argp's performance, ease of use, and its similarity to the C library it emulates. Several commenters appreciated the library's speed and small size, finding it a preferable alternative to more complex Go flag parsing libraries like pflag. However, some debated the value of mimicking the GNU style in Go, questioning its ergonomic fit. One user highlighted potential issues with error handling and suggested improvements. Others expressed concerns about compatibility and long-term maintenance. The general sentiment leaned towards cautious optimism, acknowledging argp's strengths while also raising valid concerns.

  The Hacker News post about argp, a GNU-style command line argument parser for Go, has several comments discussing its merits and drawbacks.

  One commenter points out that while they appreciate the effort, they generally prefer using Go's flag package for simpler cases and moving to a more powerful library like spf13/cobra when the needs become more complex. They feel argp sits in an awkward middle ground. This sentiment is echoed by another user who adds that cobra also handles things like help text generation and subcommand management effectively, making it a more complete solution.

  Another commenter expresses concern over the dependency on C code, viewing it as a potential disadvantage. They also question the long-term maintenance of the project and suggest exploring pure Go alternatives.

  Several users discuss the specific GNU style of argument parsing, with some appreciating its familiarity and others finding it overly complex and verbose. One commenter specifically mentions the lack of positional argument support as a drawback, preferring libraries that offer more flexibility in this area.

  There's a discussion about the "batteries included" philosophy of Go and whether a project like argp fits into that ecosystem. Some argue that the standard library's flag package is sufficient for most use cases, while others appreciate the availability of external libraries like argp for those who prefer a different style.

  One commenter mentions that while they're not currently using argp, they're keeping an eye on it for future projects, particularly those that require close compatibility with existing C codebases.

  Finally, the author of argp chimes in to clarify some points. They explain that the library aims to provide a familiar experience for developers coming from a C/GNU background and addresses the concerns about C dependencies, stating they're minimal and primarily for parsing GNU-style options. They also acknowledge the existence of other argument parsers but emphasize that argp fills a specific niche for those who prefer the GNU conventions. They further explain that POSIX-compliant short and long option parsing is available, but GNU extensions are the project's focus. They acknowledge positional arguments are currently missing and are open to considering them for the future. The author also details their motivation: they needed GNU-style parsing in a project and, unhappy with existing Go options, created argp and subsequently open-sourced it.