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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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llSuccess = .F.

//  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.

loSsh = createobject("CkSsh")

lnSshPort = 22
llSuccess = loSsh.Connect("ssh.example.com",lnSshPort)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    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.
lcPassword = "mySshPassword"

llSuccess = loSsh.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lnChannelNum = loSsh.OpenSessionChannel()
if (lnChannelNum < 0) then
    ? loSsh.LastErrorText
    release loSsh
    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.
llSuccess = loSsh.SendReqShell(lnChannelNum)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    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.
llSuccess = loSsh.ChannelSendString(lnChannelNum,"ls -l /tmp; echo DONE_MARKER" + Chr(10),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    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.
loSsh.ReadTimeoutMs = 15000

//  Receive until the marker appears in the output.
llCaseSensitive = .F.
llSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"DONE_MARKER","utf-8",llCaseSensitive)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lcOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcOutput

loSsh.Disconnect()


release loSsh