gomcli

gomcli

gomcli is a simple Go library to help developers build interactive command-line interfaces in the style of Metasploit Framework's msfconsole.

It is heavily inspired by riposte, a similar library for Python (in fact, some chunks of the code are a direct conversion to Go). However, the scope is a bit narrower, since things like output formatting are intentionally left out of the library's functionality.

It uses the Liner package under the hood. Therefore, many features already come for free, such as tab autocompletion, reverse search history, clear screen...

Usage and example

Instantiate a GomCLI, set a custom prompt and you are good to go.

import "github.com/jmreyes/gomcli"

func main() {
	cli := gomcli.New()
	cli.SetPrompt("myprompt$ ")
}

Add Commands to this instance to inform the CLI of the available options for autocompletion and execution. A Command is defined as follows:

type Command struct {
	Name       string
	Function   interface{}
	ErrHandler ErrHandler
	Completer  Completer
}

• Name: The input that will trigger the execution of the Function.
• Function: The function that will be called.
• ErrHandler: Function to allow you to decide what happens when there are arguments missing, or invalid arguments are provided (e.g. provided string cannot be converted to the int argument the Function is expecting).
• Completer: Function that returns the completions for this Command, to allow for subcommands. The subcommands will be additional Commands, with apropriate Name.

Check out the godoc for advanced configuration.

The following example tries to illustrate the basics, providing the functionality shown in the gif above.

package main

import (
	"math"
	"strings"

	"github.com/jmreyes/gomcli"
)

var cli *gomcli.GomCLI

var currentMode = "basic"

func sum(x int, y int) {
	gomcli.Printf("[+] Sum is %v\n\n", x+y)
}

func mode() {
	gomcli.Printf("[i] Current mode is %v\n\n", currentMode)
}

func modeCompleter(text string) (res []string) {
	for _, subcommand := range []string{"basic", "advanced"} {
		if strings.HasPrefix(subcommand, text) {
			res = append(res, subcommand)
		}
	}
	return
}

func modeAdvanced() {
	currentMode = "advanced"
	cli.SetPrompt("gomcli [advanced] > ")

	gomcli.Printf("[+] Advanced mode set!\n\n")

	cli.AddCommand(gomcli.Command{
		Name: "power",
		Function: func(x float64, y float64) {
			gomcli.Printf("[+] Power is %v\n\n", math.Pow(x, y))
		},
		ErrHandler: errorHandler,
	})
}

func errorHandler(c *gomcli.Command, s []string, err error) error {
    // Check out the godoc for a full list of errors!
    if err == gomcli.ErrCmdMissingArgs {
		gomcli.Printf("[-] Arguments missing!\n\n")
	} else {
		gomcli.Printf("[-] Error! Did you really use valid input?\n\n")
	}
	return nil
}

func main() {
	cli = gomcli.New()

	cli.SetPrompt("gomcli > ")
	cli.SetNotFoundHandler(func(cmd string) error {
		gomcli.Printf("[-] Command %v not found!\n\n", cmd)
		return nil
	})

	cli.SetCommands([]gomcli.Command{
		{
			Name:       "sum",
			Function:   sum,
			ErrHandler: errorHandler,
		},
		{
			Name:      "mode",
			Function:  mode,
			Completer: modeCompleter,
		},
		{
			Name:     "mode advanced",
			Function: modeAdvanced,
		},
	})

	cli.Start()
}

Dependencies

• Liner
• go-shlex