getopt: init module

getopt/getopt.go

@@ -0,0 +1,155 @@
+// getopt is a POSIX-compatible implementation of getopt(3) for Go.
+//
+// Example usage:
+//
+//	import (
+//		"os"
+//		"git.sr.ht/~sircmpwn/getopt"
+//	)
+//
+//	func main() {
+//		opts, optind, err := getopt.Getopts(os.Args, "abc:d:")
+//		if err != nil {
+//			panic(err)
+//		}
+//		for _, opt := range opts {
+//			switch opt.Option {
+//			case 'a':
+//				println("Option -a specified")
+//			case 'b':
+//				println("Option -b specified")
+//			case 'c':
+//				println("Option -c specified: " + opt.Value)
+//			case 'd':
+//				println("Option -d specified: " + opt.Value)
+//			}
+//		}
+//		println("Remaining arguments:")
+//		for _, arg := range os.Args[optind:] {
+//			println(arg)
+//		}
+//	}
+//
+// A flag[0]-like interface is also supported.
+//
+//	import (
+// 		"git.sr.ht/~sircmpwn/getopt"
+// 	)
+//
+// 	func main() {
+// 		a := getopt.Bool("a", false, "turn on option a")
+// 		b := getopt.Int("b", 1, "set b to a numerical value")
+// 		var opt string
+// 		getopt.StringVar(&opt, "c", "", "let c be specified string")
+//
+// 		err := getopt.Parse()
+// 		if err != nil {
+// 			panic(err)
+// 		}
+//
+// 		print("Value of a: ")
+// 		println(*a)
+// 		print("Value of b: ")
+// 		println(*b)
+// 		println("Value of c: " + opt)
+//
+// 		println("Remaining arguments:")
+// 		for _, arg := range getopt.Args() {
+// 			println(arg)
+// 		}
+// 	}
+//
+// [0]: https://golang.org/pkg/flag/
+package getopt
+
+import (
+	"fmt"
+	"os"
+)
+
+// In the case of "-o example", Option is 'o' and "example" is Value. For
+// options which do not take an argument, Value is "".
+type Option struct {
+	Option rune
+	Value  string
+}
+
+// This is returned when an unknown option is found in argv, but not in the
+// option spec.
+type UnknownOptionError rune
+
+func (e UnknownOptionError) Error() string {
+	return fmt.Sprintf("%s: unknown option -%c", os.Args[0], rune(e))
+}
+
+// This is returned when an option with a mandatory argument is missing that
+// argument.
+type MissingOptionError rune
+
+func (e MissingOptionError) Error() string {
+	return fmt.Sprintf("%s: expected argument for -%c", os.Args[0], rune(e))
+}
+
+// Getopts implements a POSIX-compatible options interface.
+//
+// Returns a slice of options and the index of the first non-option argument.
+//
+// If an error is returned, you must print it to stderr to be POSIX complaint.
+func Getopts(argv []string, spec string) ([]Option, int, error) {
+	optmap := make(map[rune]bool)
+	runes := []rune(spec)
+	for i, rn := range spec {
+		if rn == ':' {
+			if i == 0 {
+				continue
+			}
+			optmap[runes[i-1]] = true
+		} else {
+			optmap[rn] = false
+		}
+	}
+
+	var (
+		i    int
+		opts []Option
+	)
+	for i = 1; i < len(argv); i++ {
+		arg := argv[i]
+		runes = []rune(arg)
+		if len(arg) == 0 || arg == "-" {
+			break
+		}
+		if arg[0] != '-' {
+			break
+		}
+		if arg == "--" {
+			i++
+			break
+		}
+		for j, opt := range runes[1:] {
+			if optopt, ok := optmap[opt]; !ok {
+				opts = append(opts, Option{'?', ""})
+				return opts, i, UnknownOptionError(opt)
+			} else if optopt {
+				if j+1 < len(runes)-1 {
+					opts = append(opts, Option{opt, string(runes[j+2:])})
+					break
+				} else {
+					if i+1 >= len(argv) {
+						if len(spec) >= 1 && spec[0] == ':' {
+							opts = append(opts, Option{':', string(opt)})
+						} else {
+							return opts, i, MissingOptionError(opt)
+						}
+					} else {
+						opts = append(opts, Option{opt, argv[i+1]})
+						i++
+					}
+				}
+			} else {
+				opts = append(opts, Option{opt, ""})
+			}
+		}
+	}
+	return opts, i, nil
+}