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).

    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.

    ssh := chilkat.NewSsh()

    sshPort := 22
    success = ssh.Connect("ssh.example.com",sshPort)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        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.
    password := "mySshPassword"

    success = ssh.AuthenticatePw("mySshLogin",password)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    channelNum := ssh.OpenSessionChannel()
    if channelNum < 0 {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        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 {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    success = ssh.ChannelSendString(channelNum,"cat /var/log/syslog\n","utf-8")
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        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.
    pollTimeoutMs := 500
    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.
    result := ssh.ChannelReadAndPoll2(channelNum,pollTimeoutMs,maxNumBytes)
    if result == -1 {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

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

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

    if result > 0 {
        fmt.Println("Total bytes buffered: ", result)
    }

    output := ssh.GetReceivedText(channelNum,"utf-8")
    if ssh.LastMethodSuccess() == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    fmt.Println(*output)

    ssh.Disconnect()

    ssh.DisposeSsh()