SSH to a Cisco Switch - Processing "More" Responses

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Demonstrates connecting to a Cisco switch, entering privileged mode with the ena command, and running a command whose response is paged. Each page ends with --More-- and requires a SPACE character to request the next page.

Note: QuickShell allocates a PTY, which is what a network device console expects. The device presents an interactive prompt, and each command's output is read up to the next prompt.

import { Ssh, StringArray, StringBuilder } from '@chilkat/react-native'

async function chilkatExample() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // Demonstrates connecting to a Cisco switch, entering privileged mode, and running a command
  // whose response is paged -- each page ends with "--More--" and requires a SPACE character to
  // request the next page.

  const ssh = new Ssh();

  const port = 22;
  try {
    await ssh.connectAsync('172.16.16.100', port);
  } catch {
    console.log(ssh.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.
  const password = 'mySshPassword';

  try {
    await ssh.authenticatePwAsync('mySshLogin', password);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  const channelNum = await ssh.quickShellAsync();
  if (channelNum < 0) {
    console.log(ssh.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;

  const caseSensitive = true;

  // In unprivileged mode the switch prompt ends with ">".
  try {
    await ssh.channelReceiveUntilMatchAsync(channelNum, '>', 'utf-8', caseSensitive);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  let received: string;
  try {
    received = ssh.getReceivedText(channelNum, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  console.log(received);

  // Send "ena" to enter privileged mode.  Cisco devices expect a bare CR to terminate a command.
  try {
    await ssh.channelSendStringAsync(channelNum, 'ena\r', 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  try {
    await ssh.channelReceiveUntilMatchAsync(channelNum, 'Password:', 'utf-8', caseSensitive);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  try {
    received = ssh.getReceivedText(channelNum, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  console.log(received);

  // The enable password is separate from the login password, and likewise should come from a
  // secure source rather than being hard-coded.
  const enablePassword = 'myEnablePassword';
  try {
    await ssh.channelSendStringAsync(channelNum, enablePassword, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  try {
    await ssh.channelSendStringAsync(channelNum, '\r', 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // In privileged mode the prompt ends with "#" instead of ">".
  try {
    await ssh.channelReceiveUntilMatchAsync(channelNum, '#', 'utf-8', caseSensitive);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  try {
    received = ssh.getReceivedText(channelNum, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  console.log(received);

  // Run a command whose output is delivered a page at a time.
  try {
    await ssh.channelSendStringAsync(channelNum, 'show running-config\r', 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // Each read ends either at the device prompt (output complete) or at "--More--" (another page
  // is waiting).  Match the full prompt rather than a bare "#", because "#" also appears inside
  // configuration text and would match too early.
  const saMatch = new StringArray();
  saMatch.append('MySwitchName#');
  saMatch.append('--More--');

  const sbReceived = new StringBuilder();
  let moreComing = true;

  while (moreComing) {
    try {
      await ssh.channelReceiveUntilMatchNAsync(channelNum, saMatch, 'utf-8', caseSensitive);
    } catch {
      console.log(ssh.lastErrorText);
      return;
    }

    sbReceived.clear();
    let pageText: string;
    try {
      pageText = ssh.getReceivedText(channelNum, 'utf-8');
    } catch {
      console.log(ssh.lastErrorText);
      return;
    }

    sbReceived.append(pageText);
    console.log(pageText);

    // If this page ended with "--More--", send a SPACE to request the next page.
    moreComing = sbReceived.contains('--More--', caseSensitive);
    if (moreComing) {
      try {
        await ssh.channelSendStringAsync(channelNum, ' ', 'utf-8');
      } catch {
        console.log(ssh.lastErrorText);
        return;
      }
    }
  }

  ssh.disconnect();
}