Read an SSH Channel Until Output Goes Quiet

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Demonstrates the Chilkat Ssh.ChannelReadAndPoll method, which reads a channel in two phases: it waits for the first channel message, then keeps processing until no further data arrives for the given number of milliseconds. The first argument is the channel number and the second is the second-phase poll timeout.

The integer return value is -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or channel close was processed, or — when greater than 0 — the total bytes currently buffered for the channel (not the bytes newly received by this call).

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    --  Demonstrates the Ssh.ChannelReadAndPoll method, which reads a channel in two phases: it waits
    --  for the first channel message, then keeps processing until no more data arrives for the given
    --  number of milliseconds.  The 1st argument is the channel number and the 2nd is the poll
    --  timeout for the second phase.

    DECLARE @ssh int
    EXEC @hr = sp_OACreate 'Chilkat.Ssh', @ssh OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @sshPort int
    SELECT @sshPort = 22
    EXEC sp_OAMethod @ssh, 'Connect', @success OUT, 'ssh.example.com', @sshPort
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    --  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.
    DECLARE @password nvarchar(4000)
    SELECT @password = 'mySshPassword'

    EXEC sp_OAMethod @ssh, 'AuthenticatePw', @success OUT, 'mySshLogin', @password
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    DECLARE @channelNum int
    EXEC sp_OAMethod @ssh, 'OpenSessionChannel', @channelNum OUT
    IF @channelNum < 0
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    --  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.
    EXEC sp_OAMethod @ssh, 'SendReqShell', @success OUT, @channelNum
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    EXEC sp_OAMethod @ssh, 'ChannelSendString', @success OUT, @channelNum, 'ls -l /usr/bin' + CHAR(10), 'utf-8'
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    --  Keep reading until the output goes quiet for 500 milliseconds.
    DECLARE @pollTimeoutMs int
    SELECT @pollTimeoutMs = 500
    --  The return value is: -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or
    --  channel close was processed, or the total number of buffered bytes when greater than 0.
    DECLARE @result int
    EXEC sp_OAMethod @ssh, 'ChannelReadAndPoll', @result OUT, @channelNum, @pollTimeoutMs
    IF @result = -1
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    IF @result = -2
      BEGIN

        PRINT 'No channel data arrived before the timeout.'
      END

    IF @result = 0
      BEGIN

        PRINT 'EOF or channel close was processed.  Buffered data may still remain.'
      END

    IF @result > 0
      BEGIN

        PRINT 'Total bytes buffered: ' + @result
      END

    DECLARE @output nvarchar(4000)
    EXEC sp_OAMethod @ssh, 'GetReceivedText', @output OUT, @channelNum, 'utf-8'
    EXEC sp_OAGetProperty @ssh, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @ssh, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ssh
        RETURN
      END

    PRINT @output

    EXEC sp_OAMethod @ssh, 'Disconnect', NULL

    EXEC @hr = sp_OADestroy @ssh


END
GO