Expect reads and returns data out of order

[viralmutant]

I have a test script which write a command to host and then immediately reads it to ensure that command was executed

// Writing data
SshShellStream.Write(command + "\n");
SshShellStream.Flush();
// Reading what was written
bool rc = SshShellStream.Expect(regex, timeout == null ? TimeSpan.FromMinutes(30) : (TimeSpan)timeout, out result);
if (!rc)
{
string msg = "Ssh shell Expect time out! " + result;
LogEvents.OnDebug(msg);
throw new Exception(msg);
}

The code throws exception occasionally and the result is printed as
System.Exception: Ssh shell Expect time out! sharsysadmin@my-local-host# e dest

The output expected was
sysadmin@my-local-host# share destroy

Which is same as what was returned, but was out of order

[keithallenjackson]

First, SSH standard does not use \n for sending an Enter, but uses \r. Because of this, the remote machine is probably not getting the simulated Enter key press and the command never runs.

[viralmutant]

The command is executed on the remote machine. Just the read of the executed command is intermittently out of order. Could this be network latency issue ?

[keithallenjackson]

No, SSH uses TCP which guarantees delivery (through acknowledgements and retransmissions) and order as long as the connection is up.

Make sure you wait for the prompt before sending your command by using Expect and a regex.

[keithallenjackson]

var promptRegex = new Regex(@"(?sm)(?<banner>.*)\s+(?<prompt>.+?[>#])\s+\k<prompt>");

Shell.Write("\r");

var output = Shell.Expect(promptRegex, TimeSpan.FromSeconds(30));
var match = promptRegex.Match(output);
var prompt = match.Groups["prompt"].Value;
var banner = match Groups["banner"].Value;

Shell.WriteLine("some command");
var commandOutput = Shell.Expect(prompt, TimeSpan.FromSeconds(30));

[viralmutant]

Thanks I'll check. It seems when the error occurs, during a long running routine, the server is unable to receive the command.

After an Expect() matches and returns the string, how do I clear the rest of the stream ?
Also, after Write() do I need Flush() ?

I somehow feel, my issue is one of the already reported bugs :(
#180
#301
#302

What does \s+\k<prompt> towards the end of the regex you suggested means ?

[keithallenjackson]

\s+ means 1 or more whitespace characters
\k is a back reference to the named capture group "prompt"

[viralmutant]

Is there a workaround for any of those mentioned bugs ?

[WojciechNagorski]

This issue should be fixed by #1322