SSH -- Running Commands that Prompt for Additional Input, such as "su"

Demonstrates how to run a shell command via SSH where the shell command prompts for additional input from the client. This example demonstrates "su".

Download Chilkat Ruby Library

require 'chilkat'

#  Important: It is helpful to send the contents of the
#  ssh.LastErrorText property when requesting support.

ssh = Chilkat::CkSsh.new()

#  Any string automatically begins a fully-functional 30-day trial.
success = ssh.UnlockComponent("30-day trial")
if (success != true)
    print ssh.lastErrorText() + "\n"
    exit
end

#  Hostname may be an IP address or hostname:
hostname = "192.168.1.117"
port = 22

#  Keep a session log, which is available via the SessionLog
#  property:
ssh.put_KeepSessionLog(true)

success = ssh.Connect(hostname,port)
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  When reading, if no additional data arrives for more than
#  5 seconds, then abort:
ssh.put_IdleTimeoutMs(5000)

#  SSH Server Authentication
#  If there is no login/password required, you must still call
#  AuthenticatePw and use any values for login/password.
success = ssh.AuthenticatePw("chilkat","myPassword")
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Open a session channel.

channelNum = ssh.OpenSessionChannel()
if (channelNum < 0)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Request a pseudo-terminal
termType = "dumb"
widthInChars = 120
heightInChars = 40
pixWidth = 0
pixHeight = 0
success = ssh.SendReqPty(channelNum,termType,widthInChars,heightInChars,pixWidth,pixHeight)
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Start a shell on the channel:
success = ssh.SendReqShell(channelNum)
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Send the su command.
#  (The SSH server I'm using for testing is a Linux Ubuntu
#  system running OpenSSH.  It is important in this case to send a bare-LF
#  and not a CRLF.)

cmd = "su\n"
success = ssh.ChannelSendString(channelNum,cmd,"ansi")
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Read until we get the prompt for the password:
success = ssh.ChannelReceiveUntilMatch(channelNum,"Password:","ansi",true)
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Display what we've received so far:
print ssh.getReceivedText(channelNum,"ansi") + "\n";

#  Send the password.
#  Again, make sure it uses a bare-LF and not a CRLF.

password = "myPassword\n"
success = ssh.ChannelSendString(channelNum,password,"ansi")
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Read the response until we get the shell prompt (assuming it's successful)
#  In my case, the shell prompt is: "root@ubuntu:/home/chilkat# "
#  It will be different in your case.
success = ssh.ChannelReceiveUntilMatch(channelNum,"root@ubuntu:/home/chilkat#","ansi",true)
if (success != true)
    #  Check the last-error information and the session log...
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    #  Check to see what was received.
    print ssh.getReceivedText(channelNum,"ansi") + "\n";
    exit
end

#  Display what we've received so far.  This clears
#  the internal receive buffer, which is important.
#  After we send the command, we'll be reading until
#  the next command prompt.  If the command prompt
#  is already in the internal receive buffer, we'll think we're
#  already finished...
print ssh.getReceivedText(channelNum,"ansi") + "\n";

#  Send a command.  In this case, we are sending the "ls" command:
cmd = "ls\n"
success = ssh.ChannelSendString(channelNum,cmd,"ansi")
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Read until the next command prompt:
success = ssh.ChannelReceiveUntilMatch(channelNum,"root@ubuntu:/home/chilkat#","ansi",true)
if (success != true)
    #  Check the last-error information and the session log...
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    #  Check to see what was received.
    print ssh.getReceivedText(channelNum,"ansi") + "\n";
    exit
end

#  Display the command output:
print ssh.getReceivedText(channelNum,"ansi") + "\n";

#  You may continue sending additional commands.
#  The technique is: send the command, read until the next command prompt,
#  and then fetch/clear the internal receive buffer.

#  We're done, so shut it down..

#  Send an EOF.  This tells the server that no more data will
#  be sent on this channel.  The channel remains open, and
#  the SSH client may still receive output on this channel.
success = ssh.ChannelSendEof(channelNum)
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Close the channel:
success = ssh.ChannelSendClose(channelNum)
if (success != true)
    print ssh.lastErrorText() + "\n";
    print ssh.sessionLog() + "\n";
    exit
end

#  Disconnect
ssh.Disconnect()