Read an SSH Channel with a Byte Threshold

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Demonstrates the Chilkat Ssh.ChannelReadAndPoll2 method, which works like ChannelReadAndPoll but also returns once newly processed data brings the total buffered data to or above a byte threshold. The arguments are the channel number, the poll timeout, and the threshold.

The integer return value is -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or channel close was processed, or — when greater than 0 — the total bytes currently buffered for the channel (not the bytes newly received by this call).

bool success = false;

//  Demonstrates the Ssh.ChannelReadAndPoll2 method, which works like ChannelReadAndPoll but also
//  returns once the total buffered data reaches or exceeds a byte threshold.  The 1st argument is
//  the channel number, the 2nd is the poll timeout, and the 3rd is the byte threshold.

Chilkat.Ssh ssh = new Chilkat.Ssh();

int sshPort = 22;
success = ssh.Connect("ssh.example.com",sshPort);
if (success == false) {
    Debug.WriteLine(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.
string password = "mySshPassword";

success = ssh.AuthenticatePw("mySshLogin",password);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

int channelNum = ssh.OpenSessionChannel();
if (channelNum < 0) {
    Debug.WriteLine(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.
success = ssh.SendReqShell(channelNum);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

success = ssh.ChannelSendString(channelNum,"cat /var/log/syslog\n","utf-8");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Return when output goes quiet for 500ms, or once about 64KB has been buffered.  The
//  threshold is not a hard buffer limit -- a whole SSH packet may push the total above it.
int pollTimeoutMs = 500;
int maxNumBytes = 65536;
//  The return value is: -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or
//  channel close was processed, or the total number of buffered bytes when greater than 0.
int result = ssh.ChannelReadAndPoll2(channelNum,pollTimeoutMs,maxNumBytes);
if (result == -1) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

if (result == -2) {
    Debug.WriteLine("No channel data arrived before the timeout.");
}

if (result == 0) {
    Debug.WriteLine("EOF or channel close was processed.  Buffered data may still remain.");
}

if (result > 0) {
    Debug.WriteLine("Total bytes buffered: " + Convert.ToString(result));
}

string output = ssh.GetReceivedText(channelNum,"utf-8");
if (ssh.LastMethodSuccess == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

Debug.WriteLine(output);

ssh.Disconnect();