Receive from an SSH Channel Until a Pattern Matches

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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.

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final ssh = CkSsh();

  final sshPort = 22;
  try {
    ssh.connect('ssh.example.com', sshPort);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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.
  final password = 'mySshPassword';

  try {
    ssh.authenticatePw('mySshLogin', password);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final channelNum = ssh.openSessionChannel();
  if (channelNum < 0) {
    print(ssh.lastErrorText);
    return;
  }

  // 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.
  try {
    ssh.sendReqShell(channelNum);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // There is no prompt to wait for, so make the command itself announce when it has finished
  // by echoing a marker after it.
  try {
    ssh.channelSendString(channelNum, 'ls -l /tmp; echo DONE_MARKER\n', 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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;

  // Receive until the marker appears in the output.
  final caseSensitive = false;
  try {
    ssh.channelReceiveUntilMatch(channelNum, 'DONE_MARKER', 'utf-8', caseSensitive);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final String output;
  try {
    output = ssh.getReceivedText(channelNum, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print(output);

  ssh.disconnect();
}