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Awesome Open Source


A more traditional flag library for the go programming language


======= A more traditional flag library for the Go programming language. I also have a long history with Python, so the implimentation code looks similar to Python's argparse class.


I did not like how the flag library that comes with Go parses command line flags.


  • You can define full word flags with the -- prefix. You can define single character flags with the - prefix.

  • Example of a full word flag: --help

  • Example of a single character flag: -h

  • Single character strings can be grouped, but only for boolean types: -abcd is essentially -a, -b, -c, -d

    • This only works for boolean type flags
  • -- denotes the end of the command line flag options

    • Everything to the right of -- will not be counted as flags

Getting started

To install: go get

package main

import (

func main() {
    f := flag2.NewFlag()

    // short flag, long flag, description, default argument
    f.AddString("n", "name", "this flag wants a name as input", "billy")
    f.AddBool("b", "bool", "this flag will store true", false)

    // a help flag is added during the parse step
    options, args := f.Parse(os.Args)

    // A usage method is provided, with details about each flag

    // unfortunate side effect of interfaces
    if options["help"] == true {

    if options["name"] != nil {
        fmt.Println("The name is:", options["name"])

    fmt.Println("===== FINAL RESULTS =====")
    fmt.Println("Options:", options)
    fmt.Println("Args:", args)

The result of running this program:

go run main.go -b -n ProfOak Extra args

--- Bools ---
-b, --bool      this flag will store true
-h, --help      Display this message and exit

--- Strings ---
-n, --name      this flag wants a name as input

Name is: ProfOak

===== FINAL RESULTS =====
Options: map[help:true bool:true name:ProfOak]
Args: [Extra args]

Reference ./test/test.go for a more detailed example.

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