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https://github.com/google/goexpect

Expect for Go
https://github.com/google/goexpect

automation cli expect ssh

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Expect for Go

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README 

        
[![CircleCI](https://circleci.com/gh/google/goexpect.svg?style=svg)](https://circleci.com/gh/google/goexpect)



This package is an implementation of [Expect](https://en.wikipedia.org/wiki/Expect) in [Go](https://golang.org).



## Features:

 - Spawning and controlling local processes with real PTYs.

 - Native SSH spawner.

 - Expect backed spawner for testing.

 - Generic spawner to make implementing additional Spawners simple.

 - Has a batcher for implementing workflows without having to write extra logic

   and code.



## Options



All Spawn functions accept a variadic of type expect.Option , these are used for changing

options of the Expecter.



### CheckDuration



The Go Expecter checks for new data every two seconds as default. This can be changed by using

the CheckDuration `func CheckDuration(d time.Duration) Option`.



### Verbose



The Verbose option is used to turn on/off verbose logging for Expect/Send statements.

This option can be very useful when troubleshooting workflows since it will log every interaction

with the device.



### VerboseWriter



The VerboseWriter option can be used to change where the verbose session logs are written.

Using this option will start writing verbose output to the provided io.Writer instead of the log default.



See the [ExampleVerbose](https://github.com/google/goexpect/blob/5c8d637b0287a2ae7bb805554056728c453871e4/expect_test.go#L585) code for an example of how to use this. 



### NoCheck



The Go Expecter periodically checks that the spawned process/ssh/session/telnet etc. session is alive.

This option turns that check off.



### DebugCheck



The DebugCheck option adds debugging to the alive Check done by the Expecter, this will start logging information

every time the check is run. Can be used for troubleshooting and debugging of Spawners.



### ChangeCheck



The ChangeCheck option makes it possible to replace the Spawner Check function with a brand new one.



### SendTimeout



The SendTimeout set timeout on the `Send` command, without timeout the `Send` command will wait forewer for the expecter process.



### BufferSize



The BufferSize option provides a mechanism to configure the client io buffer size in bytes.



## Basic Examples



### networkbit.ch



An [article](http://networkbit.ch/golang-regular-expression/) with some examples was written about goexpect on [networkbit.ch](http://networkbit.ch). 



### The [Wikipedia Expect](https://en.wikipedia.org/wiki/Expect) examples.



#### Telnet



First we try to replicate the Telnet example from wikipedia as close as possible.



Interaction:



```diff

+ username:

- user\n

+ password:

- pass\n

+ %

- cmd\n

+ %

- exit\n

```



*Error checking was omitted to keep the example short*



```

package main



import (

	"flag"

	"fmt"

	"log"

	"regexp"

	"time"



	"github.com/google/goexpect"

	"github.com/google/goterm/term"

)



const (

	timeout = 10 * time.Minute

)



var (

	addr = flag.String("address", "", "address of telnet server")

	user = flag.String("user", "", "username to use")

	pass = flag.String("pass", "", "password to use")

	cmd  = flag.String("cmd", "", "command to run")



	userRE   = regexp.MustCompile("username:")

	passRE   = regexp.MustCompile("password:")

	promptRE = regexp.MustCompile("%")

)



func main() {

	flag.Parse()

	fmt.Println(term.Bluef("Telnet 1 example"))



	e, _, err := expect.Spawn(fmt.Sprintf("telnet %s", *addr), -1)

	if err != nil {

		log.Fatal(err)

	}

	defer e.Close()



	e.Expect(userRE, timeout)

	e.Send(*user + "\n")

	e.Expect(passRE, timeout)

	e.Send(*pass + "\n")

	e.Expect(promptRE, timeout)

	e.Send(*cmd + "\n")

	result, _, _ := e.Expect(promptRE, timeout)

	e.Send("exit\n")



	fmt.Println(term.Greenf("%s: result: %s\n", *cmd, result))

}



```



In essence to run and attach to a process the `expect.Spawn(,)` is used.

The spawn returns an Expecter `e` that can run `e.Expect` and `e.Send` commands to match information

in the output and Send information in.



*See the https://github.com/google/goexpect/blob/master/examples/newspawner/telnet.go  example for a slightly more fleshed out version*



#### FTP



For the FTP example we use the expect.Batch for the following interaction.



```diff

+ username:

- user\n

+ password:

- pass\n

+ ftp>

- prompt\n

+ ftp>

- mget *\n

+ ftp>'

- bye\n

```



*ftp_example.go*



```

package main



import (

	"flag"

	"fmt"

	"log"

	"time"



	"github.com/google/goexpect"

	"github.com/google/goterm/term"

)



const (

	timeout = 10 * time.Minute

)



var (

	addr = flag.String("address", "", "address of telnet server")

	user = flag.String("user", "", "username to use")

	pass = flag.String("pass", "", "password to use")

)



func main() {

	flag.Parse()

	fmt.Println(term.Bluef("Ftp 1 example"))



	e, _, err := expect.Spawn(fmt.Sprintf("ftp %s", *addr), -1)

	if err != nil {

		log.Fatal(err)

	}

	defer e.Close()



	e.ExpectBatch([]expect.Batcher{

		&expect.BExp{R: "username:"},

		&expect.BSnd{S: *user + "\n"},

		&expect.BExp{R: "password:"},

		&expect.BSnd{S: *pass + "\n"},

		&expect.BExp{R: "ftp>"},

		&expect.BSnd{S: "bin\n"},

		&expect.BExp{R: "ftp>"},

		&expect.BSnd{S: "prompt\n"},

		&expect.BExp{R: "ftp>"},

		&expect.BSnd{S: "mget *\n"},

		&expect.BExp{R: "ftp>"},

		&expect.BSnd{S: "bye\n"},

	}, timeout)



	fmt.Println(term.Greenf("All done"))

}



```



Using the expect.Batcher makes the standard Send/Expect interactions more compact and simpler to write.



#### SSH



With the SSH login example we test out the [expect.Caser](https://github.com/google/goexpect/blob/7f68e6ee0bc89860ff53a5c0d50bcfae61853506/expect.go#L388-L397)

and the [Case Tags](https://github.com/google/goexpect/blob/7f68e6ee0bc89860ff53a5c0d50bcfae61853506/expect.go#L324-L335).



Also for this we'll use the Go Expect native [SSH Spawner](https://github.com/google/goexpect/blob/7f68e6ee0bc89860ff53a5c0d50bcfae61853506/expect.go#L872-L879)

instead of spawning a process.



Interaction:



```diff

+ "Login: "

- user

+ "Password: "

- pass1

+ "Wrong password"

+ "Login"

- user

+ "Password: "

- pass2

+ router#

```



*ssh_example.go*



```

package main



import (

	"flag"

	"fmt"

	"log"

	"regexp"

	"time"



	"golang.org/x/crypto/ssh"



	"google.golang.org/grpc/codes"



	"github.com/google/goexpect"

	"github.com/google/goterm/term"

)



const (

	timeout = 10 * time.Minute

)



var (

	addr  = flag.String("address", "", "address of telnet server")

	user  = flag.String("user", "user", "username to use")

	pass1 = flag.String("pass1", "pass1", "password to use")

	pass2 = flag.String("pass2", "pass2", "alternate password to use")

)



func main() {

	flag.Parse()

	fmt.Println(term.Bluef("SSH Example"))



	sshClt, err := ssh.Dial("tcp", *addr, &ssh.ClientConfig{

		User:            *user,

		Auth:            []ssh.AuthMethod{ssh.Password(*pass1)},

		HostKeyCallback: ssh.InsecureIgnoreHostKey(),

	})

	if err != nil {

		log.Fatalf("ssh.Dial(%q) failed: %v", *addr, err)

	}

	defer sshClt.Close()



	e, _, err := expect.SpawnSSH(sshClt, timeout)

	if err != nil {

		log.Fatal(err)

	}

	defer e.Close()



	e.ExpectBatch([]expect.Batcher{

		&expect.BCas{[]expect.Caser{

			&expect.Case{R: regexp.MustCompile(`router#`), T: expect.OK()},

			&expect.Case{R: regexp.MustCompile(`Login: `), S: *user,

				T: expect.Continue(expect.NewStatus(codes.PermissionDenied, "wrong username")), Rt: 3},

			&expect.Case{R: regexp.MustCompile(`Password: `), S: *pass1, T: expect.Next(), Rt: 1},

			&expect.Case{R: regexp.MustCompile(`Password: `), S: *pass2,

				T: expect.Continue(expect.NewStatus(codes.PermissionDenied, "wrong password")), Rt: 1},

		}},

	}, timeout)



	fmt.Println(term.Greenf("All done"))

}

```



### Generic Spawner



The Go Expect package supports adding new Spawners with the `func SpawnGeneric(opt *GenOptions, timeout time.Duration, opts ...Option) (*GExpect, <-chan error, error)`

function. 



*telnet spawner*



From the [newspawner](https://github.com/google/goexpect/blob/master/examples/newspawner/telnet.go) example.



```

func telnetSpawn(addr string, timeout time.Duration, opts ...expect.Option) (expect.Expecter, <-chan error, error) {

	conn, err := telnet.Dial(network, addr)

	if err != nil {

		return nil, nil, err

	}



	resCh := make(chan error)



	return expect.SpawnGeneric(&expect.GenOptions{

		In:  conn,

		Out: conn,

		Wait: func() error {

			return <-resCh

		},

		Close: func() error {

			close(resCh)

			return conn.Close()

		},

		Check: func() bool { return true },

	}, timeout, opts...)

}

```



### Fake Spawner



The Go Expect package includes a Fake Spawner `func SpawnFake(b []Batcher, timeout time.Duration, opt ...Option) (*GExpect, <-chan error, error)`. 

This is expected to be used to simplify testing and faking of interactive workflows.



*Fake Spawner*



```

// TestExpect tests the Expect function.

func TestExpect(t *testing.T) {

	tests := []struct {

		name    string

		fail    bool

		srv     []Batcher

		timeout time.Duration

		re      *regexp.Regexp

	}{{

		name: "Match prompt",

		srv: []Batcher{

			&BSnd{`

Pretty please don't hack my chassis



router1> `},

		},

		re:      regexp.MustCompile("router1>"),

		timeout: 2 * time.Second,

	}, {

		name: "Match fail",

		fail: true,

		re:   regexp.MustCompile("router1>"),

		srv: []Batcher{

			&BSnd{`

Welcome



Router42>`},

		},

		timeout: 1 * time.Second,

	}}



	for _, tst := range tests {

		exp, _, err := SpawnFake(tst.srv, tst.timeout)

		if err != nil {

			if !tst.fail {

				t.Errorf("%s: SpawnFake failed: %v", tst.name, err)

			}

			continue

		}

		out, _, err := exp.Expect(tst.re, tst.timeout)

		if got, want := err != nil, tst.fail; got != want {

			t.Errorf("%s: Expect(%q,%v) = %t want: %t , err: %v, out: %q", tst.name, tst.re.String(), tst.timeout, got, want, err, out)

			continue

		}

	}

}

```



*Disclaimer: This is not an official Google product.*