Xbase++

SSH Remote Shell with Multiple Commands

Demonstrates running several commands one after another in a single remote shell session, retrieving each command's output separately. No PTY is requested, so each command is followed by an echoed marker that signals where its output ends.

Background: Interleaving commands and reads in one shell requires a way to know where each command's output stops. An interactive session would use the shell prompt, but without a PTY the shell is non-interactive and never prints one — so the dependable technique is to append echo SOME_MARKER to each command and read up to that marker. Retrieving the text also clears the receive buffer, which matters here: if a marker were left buffered, the next receive would match it immediately and return the wrong output.

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LOCAL nSuccess
LOCAL oSsh
LOCAL cHostname
LOCAL nPort
LOCAL cPassword
LOCAL nChannelNum
LOCAL nCaseSensitive
LOCAL cCmdOutput

nSuccess := 0

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

//  Demonstrates running several commands one after another in a single remote shell session,
//  retrieving each command's output separately.
//  
//  No PTY is requested, so the shell runs non-interactively and never prints a command prompt.
//  Because there is no prompt to synchronize on, each command is followed by an "echo" of a
//  unique marker, and the output is read up to that marker.

oSsh := CreateObject("Chilkat.Ssh")

cHostname := "ssh.example.com"
nPort := 22
nSuccess := oSsh:Connect(cHostname, nPort)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
cPassword := "mySshPassword"

nSuccess := oSsh:AuthenticatePw("mySshLogin", cPassword)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

nChannelNum := oSsh:OpenSessionChannel()
IF (nChannelNum < 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
//  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
//  echo typed commands back, and skips interactive login scripts.  The output is therefore
//  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
//  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
nSuccess := oSsh:SendReqShell(nChannelNum)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
//  which means no limit -- without it, this call waits forever if the received data never
//  contains a match.
oSsh:ReadTimeoutMs := 15000

nCaseSensitive := 1

//  ---- 1st command: change directory ----
nSuccess := oSsh:ChannelSendString(nChannelNum, "cd /tmp; echo END_OF_CMD_1" + Chr(10), "utf-8")
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

nSuccess := oSsh:ChannelReceiveUntilMatch(nChannelNum, "END_OF_CMD_1", "utf-8", nCaseSensitive)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  Retrieving the text also clears the receive buffer, which matters: if the next marker were
//  left in the buffer, the following receive would match immediately.
cCmdOutput := oSsh:GetReceivedText(nChannelNum, "utf-8")
IF (oSsh:LastMethodSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

? cCmdOutput

//  ---- 2nd command: directory listing ----
nSuccess := oSsh:ChannelSendString(nChannelNum, "ls; echo END_OF_CMD_2" + Chr(10), "utf-8")
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

nSuccess := oSsh:ChannelReceiveUntilMatch(nChannelNum, "END_OF_CMD_2", "utf-8", nCaseSensitive)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

cCmdOutput := oSsh:GetReceivedText(nChannelNum, "utf-8")
IF (oSsh:LastMethodSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

? cCmdOutput

//  ---- 3rd command: long listing, then finish the session ----
nSuccess := oSsh:ChannelSendString(nChannelNum, "ls -l" + Chr(10), "utf-8")
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  No more input will be sent.
nSuccess := oSsh:ChannelSendEof(nChannelNum)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

nSuccess := oSsh:ChannelReceiveToClose(nChannelNum)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

cCmdOutput := oSsh:GetReceivedText(nChannelNum, "utf-8")
IF (oSsh:LastMethodSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

? cCmdOutput

oSsh:Disconnect()

oSsh:destroy()