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go-ruby-getoptlong documentation

Ruby's GetoptLong getopt-style option parser in pure Go — MRI-identical messages, no cgo.

go-ruby-getoptlong/getoptlong is a faithful, pure-Go (zero cgo) reimplementation of Ruby's GetoptLong, matching reference Ruby (MRI) byte-for-byte. The module path is github.com/go-ruby-getoptlong/getoptlong.

It is a standalone, reusable library importable by any Go program, and the backend bound into go-embedded-ruby by rbgo as a native module — the same pattern as go-ruby-yaml. The dependency runs the other way: this library has no dependency on the Ruby runtime.

Status: complete — MRI byte-exact

A faithful pure-Go port of Ruby's GetoptLong, validated by a differential oracle against the system ruby — results compared byte-for-byte — at 100% coverage, gofmt + go vet clean, CI green across the six 64-bit Go targets and three OSes.

Quick taste

p, _ := getoptlong.New(os.Args[1:],
    getoptlong.Option{Names: []string{"--number", "-n"}, Flag: getoptlong.RequiredArgument},
    getoptlong.Option{Names: []string{"--verbose", "-v"}, Flag: getoptlong.OptionalArgument},
)
p.Each(func(name, argument string) {
    fmt.Printf("%-10s %q\n", name, argument)
})
fmt.Println("operands:", p.Args)

Repositories

Repo What it is
getoptlong the library — GetoptLong in pure Go
docs this documentation site (MkDocs Material, versioned with mike)
go-ruby-getoptlong.github.io the organization landing page (Hugo)
brand logo and brand assets

Principles

  • Pure Go, CGO_ENABLED=0 — trivial cross-compilation, a single static binary, no C toolchain.
  • MRI byte-exact. Output matches reference Ruby exactly, not approximately, validated by a differential oracle against the ruby binary.
  • Standalone & reusable. Extracted from rbgo's internals; no dependency on the Ruby runtime — the dependency runs the other way.
  • 100% test coverage is the target, enforced as a CI gate, across 6 arches and 3 OSes.

Where to go next

  • Why pure Go — why this slice of Ruby is deterministic enough to live as a standalone, interpreter-independent Go library.
  • Usage & API — the public surface and worked examples.
  • Roadmap — what is done and what is downstream by design.

Source lives at github.com/go-ruby-getoptlong/getoptlong.