Read Data from an SSH Channel

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Demonstrates the Chilkat Ssh.ChannelRead method, which reads incoming SSH channel messages. The only argument is the channel number; the ReadTimeoutMs property limits how long it waits. Received data is appended to the channel's receive buffer, then retrieved with a GetReceived... method.

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).

Background: SSH reading is a two-step pattern that trips people up at first: the Channel* read/poll methods move bytes from the network into an internal per-channel buffer, and a separate GetReceived... call hands that buffer to your code. A positive return is therefore a buffer total, not a count of what this call fetched. Note that a 0 return means EOF or close — buffered data can still remain and should be drained.

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    success := false

    //  Demonstrates the Ssh.ChannelRead method, which reads incoming SSH channel messages.  The only
    //  argument is the channel number.  The ReadTimeoutMs property limits how long it waits.

    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,"uname -a\n","utf-8")
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    //  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.ChannelRead(channelNum)
    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()