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 SSH / SFTP ActiveX

LOCAL loSsh
LOCAL lnSuccess
LOCAL lcHostname
LOCAL lnPort
LOCAL lnChannelNum
LOCAL lcTermType
LOCAL lnWidthInChars
LOCAL lnHeightInChars
LOCAL lnPixWidth
LOCAL lnPixHeight
LOCAL lcCmd
LOCAL lcPassword

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

loSsh = CreateObject('Chilkat.Ssh')

*  Any string automatically begins a fully-functional 30-day trial.

lnSuccess = loSsh.UnlockComponent("30-day trial")
IF (lnSuccess <> 1) THEN
    =MESSAGEBOX(loSsh.LastErrorText)
    QUIT
ENDIF

*  Hostname may be an IP address or hostname:
lcHostname = "192.168.1.117"
lnPort = 22

*  Keep a session log, which is available via the SessionLog
*  property:
loSsh.KeepSessionLog = 1

lnSuccess = loSsh.Connect(lcHostname,lnPort)
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  When reading, if no additional data arrives for more than
*  5 seconds, then abort:
loSsh.IdleTimeoutMs = 5000

*  SSH Server Authentication
*  If there is no login/password required, you must still call
*  AuthenticatePw and use any values for login/password.
lnSuccess = loSsh.AuthenticatePw("chilkat","myPassword")
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Open a session channel.

lnChannelNum = loSsh.OpenSessionChannel()
IF (lnChannelNum < 0) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Request a pseudo-terminal

lcTermType = "dumb"

lnWidthInChars = 120

lnHeightInChars = 40

lnPixWidth = 0

lnPixHeight = 0
lnSuccess = loSsh.SendReqPty(lnChannelNum,lcTermType,lnWidthInChars,lnHeightInChars,lnPixWidth,lnPixHeight)
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Start a shell on the channel:
lnSuccess = loSsh.SendReqShell(lnChannelNum)
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  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.)

lcCmd = "su" + [CHR(10)
lnSuccess = loSsh.ChannelSendString(lnChannelNum,lcCmd,"ansi")
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Read until we get the prompt for the password:
lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"Password:","ansi",1)
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Display what we've received so far:
? loSsh.GetReceivedText(lnChannelNum,"ansi")

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

lcPassword = "myPassword" + [CHR(10)
lnSuccess = loSsh.ChannelSendString(lnChannelNum,lcPassword,"ansi")
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  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.
lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"root@ubuntu:/home/chilkat#","ansi",1)
IF (lnSuccess <> 1) THEN
    *  Check the last-error information and the session log...
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    *  Check to see what was received.
    ? loSsh.GetReceivedText(lnChannelNum,"ansi")
    QUIT
ENDIF

*  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...
? loSsh.GetReceivedText(lnChannelNum,"ansi")

*  Send a command.  In this case, we are sending the "ls" command:
lcCmd = "ls" + [CHR(10)
lnSuccess = loSsh.ChannelSendString(lnChannelNum,lcCmd,"ansi")
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Read until the next command prompt:
lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"root@ubuntu:/home/chilkat#","ansi",1)
IF (lnSuccess <> 1) THEN
    *  Check the last-error information and the session log...
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    *  Check to see what was received.
    ? loSsh.GetReceivedText(lnChannelNum,"ansi")
    QUIT
ENDIF

*  Display the command output:
? loSsh.GetReceivedText(lnChannelNum,"ansi")

*  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.
lnSuccess = loSsh.ChannelSendEof(lnChannelNum)
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Close the channel:
lnSuccess = loSsh.ChannelSendClose(lnChannelNum)
IF (lnSuccess <> 1) THEN
    ? loSsh.LastErrorText
    ? loSsh.SessionLog
    QUIT
ENDIF

*  Disconnect
loSsh.Disconnect()