Xbase++

Receive from an SSH Channel Until a Pattern Matches

Demonstrates the Chilkat Ssh.ChannelReceiveUntilMatch method, which receives text until the accumulated text matches a pattern. The arguments are the channel number, the pattern, the charset, and whether matching is case-sensitive. Existing buffered text is checked before waiting for more network data.

Important: Set the ReadTimeoutMs property before calling this method. It defaults to 0, meaning no limit, so without it the call waits forever if the received data never contains a match.

Background: Driving a shell channel means knowing when the remote side has finished talking. With no PTY requested the shell is non-interactive and never prints a prompt, so the reliable signal is a marker you deliberately echo after your command. This method automates "read until you see X." The pattern syntax is deliberately minimal: literal characters plus *, which matches zero or more characters and can span line breaks. ? and bracket classes are not supported, and backslash does not escape a literal *.

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LOCAL nSuccess
LOCAL oSsh
LOCAL nSshPort
LOCAL cPassword
LOCAL nChannelNum
LOCAL nCaseSensitive
LOCAL cOutput

nSuccess := 0

//  Demonstrates the Ssh.ChannelReceiveUntilMatch method, which receives text until the
//  accumulated text matches a pattern.  The 1st argument is the channel number, the 2nd is the
//  pattern, the 3rd is the charset, and the 4th selects case-sensitive matching.  The pattern
//  supports literal characters plus "*", which matches zero or more characters.

oSsh := CreateObject("Chilkat.Ssh")

nSshPort := 22
nSuccess := oSsh:Connect("ssh.example.com", nSshPort)
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

//  There is no prompt to wait for, so make the command itself announce when it has finished
//  by echoing a marker after it.
nSuccess := oSsh:ChannelSendString(nChannelNum, "ls -l /tmp; echo DONE_MARKER" + Chr(10), "utf-8")
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

//  Receive until the marker appears in the output.
nCaseSensitive := 0
nSuccess := oSsh:ChannelReceiveUntilMatch(nChannelNum, "DONE_MARKER", "utf-8", nCaseSensitive)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

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

? cOutput

oSsh:Disconnect()

oSsh:destroy()