Expect Script SSH Example Tutorial

Filed Under: Scripts

Expect script is a great linux/unix utility. I have to deal with a lot of unix servers in my daily life, whether it’s at work or it’s my hosting server. So I need to remember a lot of SSH users, their passwords and then SU users and passwords. It’s kind of messy when the number of servers are huge. So I thought of writing a script that will automatically login me to the server.

When I first started working on this, I got stuck as how to enter the SSH password because normal unix shells don’t have any way to send the password when it gets prompted for login. Then I come to know about expect script that allows to automate the interaction with programs that opens a terminal for input.

Expect Script

expect script, expect script ssh, expect script tutorial

Expect Script is very easy to learn and as the name suggests it works by parsing the output of the command and when it matches the specified regular expression, it processes the specified instruction.

Expect Script SSH Example

Here is the script I created for automatically login to the SSH server and then login with super user and then run a simple command.

sshsudologin.expect


#!/usr/bin/expect

#Usage sshsudologin.expect <host> <ssh user> <ssh password> <su user> <su password>

set timeout 60

spawn ssh [lindex $argv 1]@[lindex $argv 0]

expect "yes/no" { 
	send "yes\r"
	expect "*?assword" { send "[lindex $argv 2]\r" }
	} "*?assword" { send "[lindex $argv 2]\r" }

expect "# " { send "su - [lindex $argv 3]\r" }
expect ": " { send "[lindex $argv 4]\r" }
expect "# " { send "ls -ltr\r" }
interact

Important Points about Expect Script

  1. Notice the first line that specifies that expect script will be used as interpreter.
  2. Expect script default timeout is 10 seconds, so I have set the timeout to 60 seconds to avoid any timeout issues if the login prompt takes time to come.
  3. Notice the expect command followed by the regular expression and then what should be send as a response. The first Yes/No choice is added to make sure that it doesn’t fail if remote server key is not already imported.
  4. The other expect regular expressions varies across the servers, for my server it ends with “#” but for some other servers it might end with “$”, so you may need to edit it accordingly. The only thing to check is that the regular expression for the expect command should matches, so that it will send the corresponding command or password.
  5. The last expect command just shows that we can send commands also once we are logged into the server.

Here is the output when I run the above expect script with correct parameters.


pankaj@Pankajs-MacBook-Pro:~$/Users/pankaj/scripts/sshloginsudo.expect 'journaldev.com' 'pankaj' 'ssh_pwd' 'su_user' 'su_pwd'
spawn ssh pankaj@journaldev.com
pankaj@journaldev.com's password: 
Last login: Sun Jun  9 19:54:17 2013 from c-67-161-57-160.hsd1.ca.comcast.net
pankaj@journal [~]# su - su_user
Password: 
su_user@journal [~]# ls -ltr
total 708
...

Extra Tips on expect script

  1. The expect script can be reused since all the information is passed as arguments, so it’s best to create alias for each one of them for quick login and save your time in typing all the parameters. For example,
    alias journal="/Users/pankaj/scripts/sshloginsudo.expect 'journaldev.com' 'pankaj' 'ssh_pwd' 'su_user' 'su_pwd'"
  2. It’s always best to use single quotes to pass the arguments, since most of the time passwords contains special characters that can cause funny results if they are not quoted.

NOTE: The above script is tested on Mac OS and Linux systems.

Reference: SourceForge Page

Comments

  1. clarkw says:

    take a look at https://github.com/clarkwang/sexpect . you can write expect scripts with shells only.

  2. Pramod says:

    I want an expect script to connect to a website, fill out a form and get back the response of server. Is it possible?

  3. shyam says:

    27.000000\t\tC1[175]
    i want to mach this expression , this is the value i get while printing it in command line , i am usng expect “27.000000\t\tC1\[175]”;
    but it not matching and giving timed out as output . its inerpretating the words correclty as i am able to see by issuing exp_internal 1 command….
    Any solutions

  4. Adhiran says:

    Hi Pankaj,

    my requirement is file transfer from Windows server(Cygwin exe is installed for SFTP) to Unix Server and vice versa. I need java code for this.

    do you have any idea about that ?

  5. Riya says:

    Hi Pankaj,

    I was trying almost the same example. I am trying to execute a script in server B from server A. My problem is the script is not exiting from SSH session.How can I get control back to script in server A
    and print some message saying the script is done.

    #Shell script in Server A
    #!/usr/bin/expect -f
    set timeout -1
    set Username “”
    set password “”
    set ipaddress “”
    set script “”

    spawn $env(SHELL)
    send “ssh $Username@$ipaddress $script\r && exit”
    expect {
    “(yes/no)?” {send “yes\r”;exp_continue}
    “password:” {send “$password\r”;interact;}
    }

  6. Vamshi says:

    How can I ssh to one more session through an existing ssh session?

  7. yassine says:

    Awesome 🙂 now I can have up to six consoles open on a remote machine and monitor its logs with a single key combination Ctrl-Alt-m, want to learn how I did ?

    http://ychaouche.informatick.net/kde

  8. Samir says:

    Hi there,

    I have a problem when trying to ssh to a solaris box using groovy script and expect

    To give you some background, I can ssh to the solaris box with no problem from command line using putty, I can also execute my groovy and expect script from Eclipse and I am able to connect.

    However when I try to do the same from a web server that is deployed on weblogic I get the following error:
    Error: java.lang.
    IllegalArgumentException: No Configuration was registered that can handle the configuration named com.sun.security.jgss.krb5.initiate

    This happens when I use

    def shell = ex.spawn(‘solarisBox’, 22, user,password)

    ex is an instantiated object of ExpectJ… a Java wrapper for expect

    if I try to use

    def shell = ex.spawn(“ssh user@solarisBox”) in my script
    shell.expect(prompt)
    shell.send(pass)

    I get Java.IOException broken pipe

    using groovy 1.5.5 and I believe the expect version is 2.0.7

    Please help, thank you so much in advance.

  9. MOHAN says:

    Could you please share the packages for send and intreact commands, as while running command getting command not found error.

    The operating system am using was RHEL 6.5 .

  10. Gowtham says:

    Hi Pankaj

    I have gone through this web page. It was very helpful to learn about expect scripts.

    I need one help from you.

    I wrote same script which you have mentioned in this page to login to remote server. After login I am going to particular path and call shell script inside expect script. Its is executing properly in terminal( I am using Linux server).

    When I am calling that script on jenkins. Its not excuting properly.

    Please help me out its very urgent. If you need some information please let me know.

    Thanks
    pawar

    1. Pankaj says:

      I am assuming you are not talking about expect script execution from jenkins, if both the script and jenkins server is running on same machine, one of the reason could be related to permission issues or path settings.

  11. Abhinadnan says:

    HEllo,

    I have a simple expect script to be executed from our automation server on a Cisco wireless controller (version – 7.6.110). I am using ssh to connect to the device as telnet is disable on it. Script reads as below:-

    # Login to device
    spawn telnet $tc_device_ip$
    expect “Login:”
    send “$tc_device_username$\n”
    expect “User:”
    send “$tc_device_username$\n”
    expect “Password:”
    send “$tc_device_password$\n”

    # Save the config
    send “save config”
    send “y\n”
    send “exit\n”

    But when i try to run it fails with below error:-

    spawn ssh 10.70.6.21

    couldn’t execute “ssh”: no such file or directory

    while executing

    “spawn ssh 10.70.6.21”

    (file “C:\Windows\Sysnative\config\systemprofile\AppData\Local\Temp\t014256.t22638” line 2)

    Created temporary file C:\Windows\system32\config\systemprofile\AppData\Local\Temp\t014256.t22638
    Executing command: E:\NA\server\ext\expect\bin\expect.exe C:\Windows\Sysnative\config\systemprofile\AppData\Local\Temp\t014256.t22638
    spawn ssh 10.70.6.21

    couldn’t execute “ssh”: no such file or directory

    while executing

    “spawn ssh 10.70.6.21”

    It seems expect is not able to recognize ssh itself and throwing an error “spawn ssh 10.70.6.21”.

    Please assist me in identifying where i am going wrong it this.

    Thanks in Advance.
    -Abhi

    1. Pankaj says:

      Hi Abhi,

      I don’t think Windows OS provide SSH, try to run the commands from the “Command Prompt” and if it works fine, then move to create expect script.

  12. LearningExpect says:

    I have a problem with Expect. I am supposed to do the following task which involves running a command script in Solaris. This command then asks the user two passwords (one after another). I am using Expect to do this task. However, I am unable to get the desired output and the script is failing. It is unable to send the password values

    #!/usr/bin/expect
    set pri_user_password [lindex $argv 0]
    set sec_user_password [lindex $argv 1]

    spawn -f
    expect “Password for property local_service_password : ” {
    send “$pri_user_password\r” }
    expect “Password for property remote_service_password: ” {
    send “$sec_user_password\r” }

    Can you tell me what the problem might be?

  13. Madhu says:

    Hi Pankaj,

    I used this and its very useful. Can you please let me know how can I do this in Java. My requirement is , I need to login to a server 1st and then remote login to another server and then do su and then run a script.

    ssh server1
    ssh server2
    su – user
    cd /path
    sh script.sh

    I need to do above commands from java. Can you please help me out !!

    Thanks,
    Madhu

  14. vikas says:

    Suppose i want to this stuff on 500 nodes, i cant do it sequentially, so for that i might want to use threading or some other way.. do you have any idea about that ?

  15. Tanky Woo says:

    You’d better add ssh options : -oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null , to avoid be asked to add into ~/.ssh/known_hosts

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