(Ruby) 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".

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

ssh = Chilkat::CkSsh.new()

# Hostname may be an IP address or hostname:
hostname = "172.16.16.46"
port = 22

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

# If receiving output from a command stalls for more than 5 seconds, then stop waiting.
ssh.put_IdleTimeoutMs(5000)

success = ssh.AuthenticatePw("myLogin","myPassword")
if (success != true)
    print ssh.lastErrorText() + "\n";
    exit
end

# Open a session channel. 
channelNum = ssh.OpenSessionChannel()
if (channelNum < 0)
    print ssh.lastErrorText() + "\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";
    exit
end

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

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

# Send the password. (This is the equivalent of typing at the shell prompt.)
# 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";
    exit
end

# Read the response until we get the shell prompt (assuming it's successful)
# In my case, the shell prompt is: "chilkat@vivoMini64:~$ "
myShellPrompt = "chilkat@vivoMini64:~$"
# It will be different in your case.
success = ssh.ChannelReceiveUntilMatch(channelNum,myShellPrompt,"ansi",true)
if (success != true)
    # Check the last-error information and the session log...
    print ssh.lastErrorText() + "\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";
    exit
end

# Read until the next command prompt:
success = ssh.ChannelReceiveUntilMatch(channelNum,myShellPrompt,"ansi",true)
if (success != true)
    # Check the last-error information and the session log...
    print ssh.lastErrorText() + "\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";
    exit
end

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

# Disconnect
ssh.Disconnect()