Added useful utility methods and default "exit" and "help" commands..

Author: abiosoft

.gitignore

@@ -1 +1,5 @@
+*~
+.DS_Store
 example/example
+.idea/
+*.iml

CHANGES.txt

@@ -0,0 +1,9 @@
+# For now, dates (DD/MM/YYYY) are used until ishell gets stable enough to warrant tags.
+# Attempts will be made to ensure non breaking updates as much as possible.
+
+12/07/2015:
+Added PrintCommands, Commands, ShowPrompt methods to Shell.
+Added default "exit" and "help" commands to Shell returned by NewShell().
+
+11/07/2015:
+Initial version.

README.md

@@ -10,6 +10,7 @@ import "github.com/abiosoft/ishell"
 
 func main(){
     // create new shell.
+    // by default, new shell includes 'exit' and 'help' commands.
     shell := ishell.NewShell()
 
 	// display welcome info.
@@ -24,35 +25,36 @@ func main(){
 		return "Hello "+name, nil
 	})
 
-    // register a function for "exit" command.
-	shell.Register("exit", func(cmd string, args []string) (string, error) {
-		shell.Stop()
-		return "bye!", nil
-	})
-
 	// start shell
 	shell.Start()
 }
 ```
 Execution
 ```
 Sample Interactive Shell
+>> help
+Commands:
+exit help greet
 >> greet Someone Somewhere
 Hello Someone Somewhere
 >> exit
-bye!
+$
 ```
 
 #### Reading input.
 ```go
 // simulate an authentication
 shell.Register("login", func(cmd string, args []string) (string, error) {
+	// disable the '>>' for cleaner same line input.
+	shell.ShowPrompt(false)
+	defer shell.ShowPrompt(true) // yes, revert after login.
+
     // get username
-	shell.Println("Username:")
+	shell.Print("Username: ")
 	username, _ := shell.ReadLine()
 
     // get password. Does not echo characters.
-	shell.Println("Password:")
+	shell.Print("Password: ")
 	password := shell.ReadPassword(false)
 
 	... // do something with username and password
@@ -62,10 +64,8 @@ shell.Register("login", func(cmd string, args []string) (string, error) {
 ```
 Execution
 ```
-Username:
->> someusername
+Username: someusername
 Password:
->>
 Authentication Successful.
 ```
 Check example code for more.
@@ -89,5 +89,7 @@ ishell is in active development and can still change significantly.
 MIT
 
 ### Credits
-* github.com/flynn/go-shlex for splitting input into command and args.
-* github.com/howeyc/gopass for reading passwords.
+Library | Use
+------- | -----
+[github.com/flynn/go-shlex](http://github.com/flynn/go-shlex) | splitting input into command and args.
+[github.com/howeyc/gopass](http://github.com/howeyc/gopass) | reading passwords.

example/main.go

@@ -13,14 +13,9 @@ func main() {
 	shell.Println("Sample Interactive Shell")
 
 	// handle exit
-	shell.Register("exit", func(cmd string, args []string) (string, error) {
-		shell.Println("Do you want to do more ? y/n:")
-		line, _ := shell.ReadLine()
-		if strings.ToLower(line) == "y" {
-			doLogin(shell)
-		}
-		shell.Stop()
-		return "bye!", nil
+	shell.Register("login", func(cmd string, args []string) (string, error) {
+		doLogin(shell)
+		return "", nil
 	})
 
 	// register a function for "greet" command.
@@ -37,12 +32,15 @@ func main() {
 }
 
 func doLogin(shell *ishell.Shell) {
+	shell.ShowPrompt(false)
+	defer shell.ShowPrompt(true)
+
 	shell.Println("Let's simulate login")
 
 	// prompt for input
-	shell.Println("Username:")
+	shell.Print("Username: ")
 	username, _ := shell.ReadLine()
-	shell.Println("Password:")
+	shell.Print("Password: ")
 	password := shell.ReadPassword(false)
 
 	// do something with username and password

functions.go

@@ -0,0 +1,25 @@
+package ishell
+
+// CmdFunc represents a command function that is called after an input to the shell.
+// The shell input is split into command and arguments like cli args.
+// The shell will print output if output != "".
+type CmdFunc func(command string, args []string) (output string, err error)
+
+func exitFunc(s *Shell) CmdFunc {
+	return func(command string, args []string) (output string, err error) {
+		s.Stop()
+		return "", nil
+	}
+}
+
+func helpFunc(s *Shell) CmdFunc{
+	return func(command string, args []string) (output string, err error) {
+		s.PrintCommands()
+		return "", nil
+	}
+}
+
+func addDefaultFuncs(s *Shell){
+	s.Register("exit", exitFunc(s))
+	s.Register("help", helpFunc(s))
+}

ishell.go

@@ -6,46 +6,44 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"sort"
 	"strings"
 	"sync"
 
 	"github.com/flynn/go-shlex"
 	"github.com/howeyc/gopass"
 )
 
-type (
-	// CmdFunc represents a command function that is called after an input to the shell.
-	// The shell input is split into command and arguments like cli args.
-	// The shell will print output if output != "".
-	CmdFunc func(command string, args []string) (output string, err error)
-
-	Shell struct {
-		prompt      string
-		functions   map[string]CmdFunc
-		generic     CmdFunc
-		reader      *shellReader
-		writer      io.Writer
-		active      bool
-		activeMutex sync.RWMutex
-		haltChan    chan struct{}
-	}
-)
-
 const (
 	defaultPrompt = ">> "
 )
 
+type Shell struct {
+	prompt      string
+	showPrompt  bool
+	functions   map[string]CmdFunc
+	generic     CmdFunc
+	reader      *shellReader
+	writer      io.Writer
+	active      bool
+	activeMutex sync.RWMutex
+	haltChan    chan struct{}
+}
+
 // NewShell creates a new shell with default settings. Uses standard output and default prompt ">>".
 func NewShell() *Shell {
-	return &Shell{
-		prompt:    defaultPrompt,
-		functions: make(map[string]CmdFunc),
+	shell := &Shell{
+		prompt:     defaultPrompt,
+		showPrompt: true,
+		functions:  make(map[string]CmdFunc),
 		reader: &shellReader{
 			scanner: bufio.NewReader(os.Stdin),
 		},
 		writer:   os.Stdout,
 		haltChan: make(chan struct{}),
 	}
+	addDefaultFuncs(shell)
+	return shell
 }
 
 // Start starts the shell. It reads inputs from standard input and calls registered functions
@@ -184,7 +182,9 @@ func (s *Shell) ReadLine() (line string, err error) {
 }
 
 func (s *Shell) readLine() (line string, err error) {
-	s.Print(s.prompt)
+	if s.showPrompt {
+		s.Print(s.prompt)
+	}
 	consumer := make(chan lineString)
 	s.reader.ReadLine(consumer)
 	ls := <-consumer
@@ -196,10 +196,12 @@ func (s *Shell) nextLine() {
 }
 
 // ReadPassword reads password from standard input without echoing the characters.
-// If mask is true, each chracter will be represented with astericks '*'. Note that
+// If mask is true, each character will be represented with asterisks '*'. Note that
 // this only works as expected when the standard input is a terminal.
 func (s *Shell) ReadPassword(mask bool) string {
-	fmt.Fprint(s.writer, s.prompt)
+	if s.showPrompt {
+		s.Print(s.prompt)
+	}
 	if mask {
 		return string(gopass.GetPasswdMasked())
 	}
@@ -216,7 +218,7 @@ func (s *Shell) Print(val ...interface{}) {
 	fmt.Fprint(s.writer, val...)
 }
 
-// Register registers a function for command.
+// Register registers a function for command. It overwrites existing function, if any.
 func (s *Shell) Register(command string, function CmdFunc) {
 	s.functions[command] = function
 }
@@ -239,7 +241,32 @@ func (s *Shell) SetPrompt(prompt string) {
 	s.prompt = prompt
 }
 
+// ShowPrompt sets whether prompt should show when requesting input for ReadLine and ReadPassword.
+// Defaults to true.
+func (s *Shell) ShowPrompt(show bool) {
+	s.showPrompt = show
+}
+
 // SetOut sets the writer to write outputs to.
 func (s *Shell) SetOut(writer io.Writer) {
 	s.writer = writer
 }
+
+// PrintCommands prints a space separated list of registered commands to the shell.
+func (s *Shell) PrintCommands() {
+	out := strings.Join(s.Commands(), " ")
+	if out != "" {
+		s.Println("Commands:")
+		s.Println(out)
+	}
+}
+
+// Commands returns a sorted list of all registered commands.
+func (s *Shell) Commands() []string {
+	var commands []string
+	for command := range s.functions {
+		commands = append(commands, command)
+	}
+	sort.Strings(commands)
+	return commands
+}