initial version

.gitattributes

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+*	-text

.github/dependabot.yml

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+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"

.github/workflows/go.yml

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+name: Go
+
+on: [push]
+
+env:
+  GO_VERSION: '>=1.22.0'
+
+jobs:
+
+  build:
+    name: Build
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+    steps:
+
+    - uses: actions/checkout@v4
+
+    - uses: actions/setup-go@v5
+      with:
+        go-version: ${{ env.GO_VERSION }}
+
+    - run: go test
+
+    - run: go build
+
+# based on: github.com/koron-go/_skeleton/.github/workflows/go.yml

.gitignore

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+*~
+default.pgo
+tags
+tmp/

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2024 MURAOKA Taro <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

Makefile

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+TEST_PACKAGE ?= ./...
+
+.PHONY: build
+build:
+	go build -gcflags '-e' ./...
+
+.PHONY: test
+test:
+	go test $(TEST_PACKAGE)
+
+.PHONY: bench
+bench:
+	go test -bench $(TEST_PACKAGE)
+
+.PHONY: tags
+tags:
+	gotags -f tags -R .
+
+.PHONY: cover
+cover:
+	mkdir -p tmp
+	go test -coverprofile tmp/_cover.out $(TEST_PACKAGE)
+	go tool cover -html tmp/_cover.out -o tmp/cover.html
+
+.PHONY: checkall
+checkall: vet staticcheck
+
+.PHONY: vet
+vet:
+	go vet $(TEST_PACKAGE)
+
+.PHONY: staticcheck
+staticcheck:
+	staticcheck $(TEST_PACKAGE)
+
+.PHONY: clean
+clean:
+	go clean
+	rm -f tags
+	rm -f tmp/_cover.out tmp/cover.html
+
+# based on: github.com/koron-go/_skeleton/Makefile

README.md

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+# koron-go/getopt
+
+[![PkgGoDev](https://pkg.go.dev/badge/github.com/koron-go/getopt)](https://pkg.go.dev/github.com/koron-go/getopt)
+[![Actions/Go](https://github.com/koron-go/getopt/workflows/Go/badge.svg)](https://github.com/koron-go/getopt/actions?query=workflow%3AGo)
+[![Go Report Card](https://goreportcard.com/badge/github.com/koron-go/getopt)](https://goreportcard.com/report/github.com/koron-go/getopt)
+
+Package getopt provides the good old getopt function as a Go iterator.
+
+## Getting started
+
+Install and upgrade:
+
+```
+go get github.com/koron-go/getopt@latest
+```
+
+Short example:
+
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/koron-go/getopt"
+)
+
+func usage() {
+	// TODO: Show usage and exit.
+	os.Exit(1)
+}
+
+func main() {
+	var bflag bool
+	var file *os.File
+
+	for opt, err := range getopt.Getopt(os.Args[1:], "bf:") {
+		if err != nil {
+			log.Fatalf("getopt failed: opt=%+v: %s", opt, err)
+		}
+		switch opt.Name {
+		case 'b':
+			bflag = true
+		case 'f':
+			f, err := os.Open(*opt.Arg)
+			if err != nil {
+				log.Fatalf("failed to open a file: %s", err)
+			}
+			defer f.Close()
+			file = f
+		default:
+			usage()
+		}
+	}
+
+	// TODO: Do your task with bflag, file, and getopt.RestArgs
+	log.Printf("Do your task with bflag=%t f=%+v getopt.RestArgs=%+v", bflag, file, getopt.RestArgs)
+}
+```

getopt.go

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+// Package getopt provides the good old getopt function as a Go iterator.
+package getopt
+
+import (
+	"errors"
+	"fmt"
+	"iter"
+	"strings"
+	"unicode/utf8"
+)
+
+type Option struct {
+	Name rune
+	Arg  *string
+}
+
+func parseOptstring(optstring string) map[rune]int {
+	opts := map[rune]int{}
+	var last rune
+	for _, r := range optstring {
+		if r == ':' {
+			if last != 0 {
+				opts[last]++
+			}
+			continue
+		}
+		if _, ok := opts[r]; !ok {
+			opts[r] = 0
+		}
+		last = r
+	}
+	return opts
+}
+
+var RestArgs []string
+
+func Getopt(args []string, optstring string) iter.Seq2[Option, error] {
+	opts := parseOptstring(optstring)
+	return func(yield func(Option, error) bool) {
+		for i := 0; i < len(args); i++ {
+			curr := args[i]
+			if !strings.HasPrefix(curr, "-") {
+				// No options.
+				RestArgs = args[i:]
+				return
+			}
+			switch curr {
+			case "-":
+				RestArgs = args[i:]
+				yield(Option{Name: 0, Arg: nil}, errors.New("a single \"-\" is not supported"))
+				return
+			case "--":
+				RestArgs = args[i+1:]
+				return
+			default:
+				curr = curr[1:]
+			}
+
+			for j, opt := range curr {
+				optCnt, ok := opts[opt]
+				// An option ":" is not allowed.
+				// Options not included in opts are not allowed.
+				if opt == ':' || !ok {
+					RestArgs = args[i+1:]
+					if !yield(Option{Name: opt, Arg: nil}, fmt.Errorf("illegal option: '%c'", opt)) {
+						return
+					}
+					continue
+				}
+				// No arguments required.
+				if optCnt == 0 {
+					RestArgs = args[i+1:]
+					if !yield(Option{Name: opt, Arg: nil}, nil) {
+						return
+					}
+					continue
+				}
+				// Treat the rest of "curr" as the argument, if available.
+				if tail := j + utf8.RuneLen(opt); tail < len(curr) {
+					RestArgs = args[i+1:]
+					arg := curr[tail:]
+					if !yield(Option{Name: opt, Arg: &arg}, nil) {
+						return
+					}
+					break
+				}
+				// Use next args as the argument, if available.
+				if i+1 < len(args) {
+					RestArgs = args[i+2:]
+					if !yield(Option{Name: opt, Arg: &args[i+1]}, nil) {
+						return
+					}
+					i++
+					break
+				}
+				// No arguments found.
+				RestArgs = nil
+				yield(Option{Name: opt, Arg: nil}, fmt.Errorf("no arguments supplied: '%c'", opt))
+				return
+			}
+		}
+	}
+}