README.md

lesiw.io/flag

A flag parser for the lazy. Follows the POSIX utility conventions plus GNU --longopts.

So, for example, -abcd could be four boolean flags, or -b could be a string flag that considers cd to be the argument passed to it.

Pass in an io.Writer when creating a flag.Set and the Parse method will write errors and usage help messages directly to that writer. If Parse returns an error, it is recommended that the program author exit as soon as possible without additional output.

Aliases can be made at flag definition time by passing in comma-separated flag names.

Example

package main

import (
    "fmt"
    "os"

    "lesiw.io/flag"
)

var (
    flags = flag.NewSet(os.Stderr, "sandbox [-w WORD] [-n NUM] [-b] ARGS...")
    word  = flags.String("w,word", "a string")
    num   = flags.Int("n,num", "an int")
    bool  = flags.Bool("b,bool", "a bool")
)

func main() {
    os.Exit(run())
}

func run() int {
    // Playground note: Replace os.Args with other strings to test.
    if err := flags.Parse(os.Args[1:]...); err != nil {
        return 1
    }
    if len(flags.Args) < 1 {
        flags.PrintError("at least one arg is required")
        return 1
    }

    fmt.Println("word:", *word)
    fmt.Println("num:", *num)
    fmt.Println("bool:", *bool)
    fmt.Println("args:", flags.Args)

    return 0
}

▶️ Run this example on the Go Playground