> For the complete documentation index, see [llms.txt](https://ineelhere.gitbook.io/code-with-go/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ineelhere.gitbook.io/code-with-go/71-command-line-subcommands.md).

# Command-Line Subcommands

This Go program demonstrates the use of subcommands with different sets of flags using the `flag` package. It allows you to run the program with either a "foo" or "bar" subcommand, each having its own set of flags. Let's break down the code with inline comments:

```go
package main

import (
	"flag"
	"fmt"
	"os"
)

func main() {
	// Define flags for the 'foo' subcommand
	fooCmd := flag.NewFlagSet("foo", flag.ExitOnError)
	fooEnable := fooCmd.Bool("enable", false, "enable")
	fooName := fooCmd.String("name", "", "name")

	// Define flags for the 'bar' subcommand
	barCmd := flag.NewFlagSet("bar", flag.ExitOnError)
	barLevel := barCmd.Int("level", 0, "level")

	// Check if there are enough arguments
	if len(os.Args) < 2 {
		fmt.Println("expected 'foo' or 'bar' subcommands")
		os.Exit(1)
	}

	// Determine the subcommand and parse its specific flags
	switch os.Args[1] {
	case "foo":
		fooCmd.Parse(os.Args[2:])
		fmt.Println("subcommand 'foo'")
		fmt.Println("  enable:", *fooEnable)
		fmt.Println("  name:", *fooName)
		fmt.Println("  tail:", fooCmd.Args())
	case "bar":
		barCmd.Parse(os.Args[2:])
		fmt.Println("subcommand 'bar'")
		fmt.Println("  level:", *barLevel)
		fmt.Println("  tail:", barCmd.Args())
	default:
		fmt.Println("expected 'foo' or 'bar' subcommands")
		os.Exit(1)
	}
}
```

Explanation:

1. **Defining Flags for Subcommands:**
   * The program defines two sets of flags using `flag.NewFlagSet` for the 'foo' and 'bar' subcommands.
2. **Parsing Subcommands:**
   * The program checks the number of command-line arguments. If there are not enough arguments, it prints an error message and exits.
3. **Switching Between Subcommands:**
   * The program uses a switch statement to determine whether the first argument is "foo" or "bar."
4. **Parsing Subcommand-Specific Flags:**
   * Depending on the subcommand, it parses the specific set of flags for that subcommand using `fooCmd.Parse` or `barCmd.Parse`.
5. **Printing Results:**
   * After parsing the subcommand-specific flags, the program prints the results.

You can run the program with commands like:

```bash
go run main.go foo -enable -name John arg1 arg2
```

or

```bash
go run main.go bar -level 5 arg1 arg2
```

This allows you to have different flags for different subcommands.