How to Create Independent FlagSets in GoLang for Subcommands?

Independent FlagSets in GoLang

Introduction:

FlagSets in Go provide a mechanism for defining and parsing command-line flags. While the documentation suggests the ability to create independent sets for implementing subcommands in a user interface, it remains unclear how to achieve this functionality in practice.

Question:

How can we define independent FlagSets in GoLang to support subcommands in a command-line interface?

Answer:

Distinguishing Between Subcommands

To achieve independent FlagSets, the key distinction lies in identifying the subcommand before parsing flags. Here's how:

1. Create the FlagSets:

Define multiple FlagSets, one for each subcommand.

f1 := flag.NewFlagSet("f1", flag.ContinueOnError)
reset := f2.Bool("reset", false, "")

2. Distinguish Subcommands:

Examine the command-line arguments to identify the active subcommand. For example, if the prefix of the command is "apply", execute FlagSet "f1".

switch os.Args[1] {
  case "apply":
    f1.Parse(os.Args[2:])
  case "reset":
    f2.Parse(os.Args[2:])
}

By separating the parsing of different FlagSets based on subcommands, we can maintain independent sets of flags that apply only to their respective subcommands.

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