Xojo Plugin

Receive from an SSH Channel Until Any Pattern Matches

Demonstrates the Chilkat Ssh.ChannelReceiveUntilMatchN method, which works like ChannelReceiveUntilMatch but returns when any pattern in a StringArray matches. The arguments are the channel number, the pattern array, the charset, and case sensitivity. The array must contain at least one element.

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: A command often has more than one possible outcome, and your code should react to whichever occurs rather than hang waiting for one specific string. A common non-interactive pattern is to have the command print one marker on success and a different marker on failure, then match on the set. (With no PTY there is no shell prompt to match against, so markers you emit yourself are the dependable signal.) The first matching content in the stream wins; array order does not override an earlier token. Empty elements are ignored and duplicates are allowed.

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Dim success As Boolean
success = False

//  Demonstrates the Ssh.ChannelReceiveUntilMatchN method, which receives text until ANY pattern
//  in a StringArray is matched.  The 1st argument is the channel number, the 2nd is the array of
//  patterns, the 3rd is the charset, and the 4th selects case-sensitive matching.

Dim ssh As New Chilkat.Ssh

Dim sshPort As Int32
sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

//  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.
Dim password As String
password = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin",password)
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

Dim channelNum As Int32
channelNum = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

//  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 = ssh.SendReqShell(channelNum)
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

//  There is no prompt to match on.  Instead, run a command that prints one marker on success
//  and a different marker on failure, then wait for whichever appears first.
success = ssh.ChannelSendString(channelNum,"test -f /etc/hosts && echo OK_MARKER || echo ERR_MARKER" + EndOfLine.Unix,"utf-8")
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

Dim patterns As New Chilkat.StringArray
success = patterns.Append("OK_MARKER")
success = patterns.Append("ERR_MARKER")

//  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.
ssh.ReadTimeoutMs = 15000

Dim caseSensitive As Boolean
caseSensitive = False
success = ssh.ChannelReceiveUntilMatchN(channelNum,patterns,"utf-8",caseSensitive)
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

Dim output As String
output = ssh.GetReceivedText(channelNum,"utf-8")
If (ssh.LastMethodSuccess = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

System.DebugLog(output)

ssh.Disconnect