PureBasic

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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IncludeFile "CkSsh.pb"

Procedure ChilkatExample()

    success.i = 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.

    ssh.i = CkSsh::ckCreate()
    If ssh.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    hostname.s = "ssh.example.com"
    port.i = 22
    success = CkSsh::ckConnect(ssh,hostname,port)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    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.
    password.s = "mySshPassword"

    success = CkSsh::ckAuthenticatePw(ssh,"mySshLogin",password)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    channelNum.i = CkSsh::ckOpenSessionChannel(ssh)
    If channelNum < 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    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.
    success = CkSsh::ckSendReqShell(ssh,channelNum)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    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.
    CkSsh::setCkReadTimeoutMs(ssh, 15000)

    caseSensitive.i = 1

    ;  ---- 1st command: change directory ----
    success = CkSsh::ckChannelSendString(ssh,channelNum,"cd /tmp; echo END_OF_CMD_1" + Chr(10),"utf-8")
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    success = CkSsh::ckChannelReceiveUntilMatch(ssh,channelNum,"END_OF_CMD_1","utf-8",caseSensitive)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    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.
    cmdOutput.s = CkSsh::ckGetReceivedText(ssh,channelNum,"utf-8")
    If CkSsh::ckLastMethodSuccess(ssh) = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    Debug cmdOutput

    ;  ---- 2nd command: directory listing ----
    success = CkSsh::ckChannelSendString(ssh,channelNum,"ls; echo END_OF_CMD_2" + Chr(10),"utf-8")
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    success = CkSsh::ckChannelReceiveUntilMatch(ssh,channelNum,"END_OF_CMD_2","utf-8",caseSensitive)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    cmdOutput = CkSsh::ckGetReceivedText(ssh,channelNum,"utf-8")
    If CkSsh::ckLastMethodSuccess(ssh) = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    Debug cmdOutput

    ;  ---- 3rd command: long listing, then finish the session ----
    success = CkSsh::ckChannelSendString(ssh,channelNum,"ls -l" + Chr(10),"utf-8")
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    ;  No more input will be sent.
    success = CkSsh::ckChannelSendEof(ssh,channelNum)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    success = CkSsh::ckChannelReceiveToClose(ssh,channelNum)
    If success = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    cmdOutput = CkSsh::ckGetReceivedText(ssh,channelNum,"utf-8")
    If CkSsh::ckLastMethodSuccess(ssh) = 0
        Debug CkSsh::ckLastErrorText(ssh)
        CkSsh::ckDispose(ssh)
        ProcedureReturn
    EndIf

    Debug cmdOutput

    CkSsh::ckDisconnect(ssh)


    CkSsh::ckDispose(ssh)


    ProcedureReturn
EndProcedure