Windows: console messages are not displayed into the current console

[laurentj]

Windows: console messages are not displayed into the current console

[matthewkastor]

That console closes when the xulrunner or firefox closes. It's a good feature to have. If you want the console to stay around then don't exit the program. I ran the initial-tests.js and had to comment out the exit command to keep the window open. After I read the results I closed the window and the process exited as expected.

[matthewkastor]

There are notes about the console on windows in this article on MDN It says you can redirect the console output to a file by launching firefox without the -console switch like this: firefox.exe > log.txt 2>&1

I tried that and it didn't work for me. I thought that if it did I might be able to find some obscure batch magic to redirect to the output to a console that wouldn't be closed when Gecko exits.

[laurentj]

I found a solution. Not an optimal one because we cannot see messages at realtime. We saw them at the end at least.
Can it be an acceptable solution?

[matthewkastor]

It's acceptable as long as you don't rely on people being able to see it before slimerjs closes. In other words, if the console is only paid any attention when running tests or debugging why an application won't start. Once an app is capable of displaying a window then the built in error console is a much better place to log things as it has good formatting and can be given access to the chrome. Being that the command line is only a message board for stdout I doubt that anyone would be interested in it aside from troubleshooting application start up. I mean, we're not recompiling custom versions of Gecko so...

I did look around for a way to redirect the output so windows, linux, and mac would all be able to see the dump messages in realtime. It appears that redirecting to CON is supposed to be a way of explicitly sending information to the console.

firefox.exe 1> CON 2>&1

The thing is, it seems that either what I was reading is wrong, or that firefox is just too smart to be put into the calling console on windows.

There were more complicated solutions involving visual basic that might work but, then there would be some compiling of the executable and other irritating work for something that just won't be all that useful. If you want to look into it, there is a massive and complex example of redirecting sterr in realtime on msdn You can do the same thing with stdout and have the handler functions for OutputDataReceived and ErrorDataReceived just Console.WriteLine(DataReceivedEventArgs.Data) but, I didn't quite have the patience to test it with firefox. Like I said, it would need to be compiled into an executable in order to be easy for people to use.

[matthewkastor]

I found some patience and curiosity. I've got a Visual Basic file that can redirect Firefox's stdout and stderr back to the console that opened it. If you compile it into a console application and just run the exe file, it will do the same thing that running Firefox with the -console switch does. If you run the exe from a command prompt then Firefox's output will be redirected to it and everything will seem normal (realtime dump logging). I've got it compiled already and can send a pull request if you're interested. I could also eliminate all the other logic in the batch file by bringing it into this executable if you want.

Here is the VB code, note that I've got to trick Firefox by feeding it an argument to redirect it's output to a text file and then I can grab the output and send it to the console instead. . . weird huh? It would probably make a horrible looking batch file 1> tmp.txt 2>&1 CON< . . . err. . . umm tee? . . . we don't have tee, I could fake it with this though:

Imports System
Imports System.Diagnostics
Imports System.IO

Module Module1

    Public Sub Main()
        Try
            FirefoxyConsoleRedirector()
        Catch e As InvalidOperationException
            Console.WriteLine("Exception:")
            Console.WriteLine(e.ToString())
        End Try
    End Sub

    Public Sub FirefoxyConsoleRedirector()
        Dim ffloc As String = Nothing
        Try
            ffloc = Environment.GetEnvironmentVariable("programfiles(x86)")
        Catch ex As Exception
            Try
                ffloc = Environment.GetEnvironmentVariable("programfiles")
            Catch exc As Exception
                Console.WriteLine("Could not retreive a programfiles" _
                                  & "environment variable on your system!")
                Exit Sub
            End Try
        End Try
        ffloc = ffloc & "\Mozilla Firefox\firefox.exe"
        If Not File.Exists(ffloc) Then
            Console.WriteLine("Firefox not found at " & ffloc)
            Exit Sub
        End If
        Dim firefoxen As New Process()
        firefoxen.StartInfo.FileName = ffloc
        firefoxen.StartInfo.Arguments = """>tmp.txt 1>&2"""
        firefoxen.StartInfo.UseShellExecute = False
        firefoxen.StartInfo.RedirectStandardError = True
        firefoxen.StartInfo.RedirectStandardOutput = True
        AddHandler firefoxen.OutputDataReceived, AddressOf ConsoleLogger
        AddHandler firefoxen.ErrorDataReceived, AddressOf ConsoleLogger
        firefoxen.Start()
        firefoxen.BeginOutputReadLine()
        firefoxen.BeginErrorReadLine()
        firefoxen.WaitForExit()
        firefoxen.Close()
    End Sub

    Private Sub ConsoleLogger(sendingProcess As Object, _
                outLine As DataReceivedEventArgs)
        Console.WriteLine(outLine.Data)
    End Sub

End Module

[matthewkastor]

#12 completely resolves this issue. The console output is now redirected to the console that launched the Gecko runtime in real time all the time. The user can then do whatever they would like with it.

[dksarangoung]

There is a Windows version of tee that correctly outputs redirection to the console in real time.

[matthewkastor]

Nice! Is it open source? Do you have a link to it?

[dksarangoung]

https://code.google.com/p/wintee

It's released under the MPL. Copy wtee.exe to the folder where slimerjs lives and redirect the output to it:

yadda yadda slimerjs | wtee

Not the best solution, but it works OK for me.

[matthewkastor]

It sounds like wintee has gone through a lot more testing and use by the developer than what I did with my code. For sure, if I had found it when I thought about helping slimerjs behave similarly on Windows and Linux I'd have just used it and not taken the time to build a silly project in VB. :D

That said, I can't say what @laurentj may or may not have done to improve what I scribbled out so for sure, this might be a better option than my repo but, it may not be quite as awesome as whatever Laurent has done in the 10 months since we argued over just how awesome Firefox and Windows consoles are. :D Looking at issue #105 leads me to believe he may not be using my code anymore at all? Looking at the bugzilla reports it looks like the weird Windows console behavior of late was something in Mozilla's code around v. 15 of FF.

I'm not saying my scribbles are perfect, they could be wrong, but they're pretty much doing what wintee is doing in that the code is set up to redirect stdin, stderr, and stdout to as many individual endpoints as you want in real time. There are a couple examples of how to use it at https://github.com/matthewkastor/redirector and for sure, if you know a tiny bit of VB you can do a lot more with my code than you can do with wintee.

For real though, it was kinda rude to say "correctly outputs redirection" because for sure my code correctly redirects to the console. I think getting messages to the command console on Firefox requires the dump (https://developer.mozilla.org/en-US/docs/Web/API/Window.dump) command or something, and if I remember correctly the messages dumped need to be terminated by newlines or they won't show up. People always make the mistake of thinking console.log will write to the command console but that writes to the browsers console object, unless Firefox changed it to write to the command console as well. Could be, I don't know, I haven't been messing around with this area of esoterica in months.

Whatever you do to get the job done, if it works better than what's currently in slimerjs you should definitely share it. Working with strangers on awesome projects like this is really a lot of fun. :D

[dksarangoung]

window.dump() is a non-standard extension.

[matthewkastor]

lolz, so how do you send messages to the command console from your app? Has laurent overridden console.log so it dumps to the command console?

/**
 * Turns console.log into window.dump
 * @author <a href="[email protected]">Matthew Kastor</a>
 */
function slimer_dump () {
    var args = Array.prototype.slice.call(arguments, 0);
    var message = args.reduce(function (prev, curr) {
        if (curr instanceof Function) {
            curr = String(curr);
        }
        if (curr instanceof Object) {
            curr = JSON.stringify(curr);
        }
        return String(prev) + ' ' + String(curr);
    }, '');
    message = message.slice(1);
    // because really, what's standard about what you're doing with slimerjs?
    dump(message + '\r\n');
}
console.log = slimer_dump;

// usage?

var z = function wee(){};
z.a = 'banana';
var a = {"something":5};
var b = [1,2,3,4];

console.log('foo', z, a, b, 'bar');