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).

func chilkatTest() {
    var success: Bool = 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.

    let ssh = CkoSsh()!

    var sshPort: Int = 22
    success = ssh.connect(hostname: "ssh.example.com", port: sshPort)
    if success == false {
        print("\(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.
    var password: String? = "mySshPassword"

    success = ssh.authenticatePw(login: "mySshLogin", password: password)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    var channelNum: Int = ssh.openSessionChannel().intValue
    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.
    success = ssh.sendReqShell(channelNum: channelNum)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    success = ssh.channelSendString(channelNum: channelNum, strData: "cat /var/log/syslog\n", charset: "utf-8")
    if success == false {
        print("\(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.
    var pollTimeoutMs: Int = 500
    var maxNumBytes: Int = 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.
    var result: Int = ssh.channelReadAndPoll2(channelNum: channelNum, pollTimeoutMs: pollTimeoutMs, maxNumBytes: maxNumBytes).intValue
    if result == -1 {
        print("\(ssh.lastErrorText!)")
        return
    }

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

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

    if result > 0 {
        print("Total bytes buffered: \(result)")
    }

    var output: String? = ssh.getReceivedText(channelNum: channelNum, charset: "utf-8")
    if ssh.lastMethodSuccess == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    print("\(output!)")

    ssh.disconnect()

}