Console app async control

[Alistair George]

Hi all.
A win gui has to run a console (cmd) app, desirably the cmd window is
hidden, which I will do by placing outside the view area.
The GUI must be able to parse the output from cmd and do various things
like show a progress meter etc. It should also be able to gracefully
close the cmd window if it hangs or user needs the thread to abort.
Would I be correct in assuming the cmd should be started in a thread
with async coms?
MethodInvoker with BeginInvoke?
Appreciate any pointers to articles on this subject (google search
reveals few).
Thank you.

[Marc Gravell]

Re: Console app async control

If you look at ProcessStartInf o, you can suppress the visual console
(IIRC) with CreateNoWindow = true, and capture the output by setting
RedirectStandar dOutput = false, UseShellExecute = false, and reading
from Process.Standar dOutput once you have started the command.

When running a win-ui, the easiest option is to do the reading (from
StandardOutput) on a workder thread (not the UI thread), and then
(when you read something interesting) use yourForm.BeginI nvoke() to
notify the UI. There is also an event-driven mechanism
(Process.Output DataReceived), but this is trickier.

I'll put an example together if you like...

Marc

[Marc Gravell]

Re: Console app async control

(exe)

using System;
using System.IO;

class Program {
static int Main(string[] args) {
try {
string root = args.Length == 1 ? args[0] :
Environment.Cur rentDirectory;
string[] dirs = Directory.GetDi rectories(args[0], "*.*",
SearchOption.Al lDirectories);
int count = dirs.Length, lastPercent = -1;
for (int i = 0; i < count; i++) {
int percent = (i * 100) / count;
if (percent != lastPercent) {
Console.WriteLi ne(percent.ToSt ring() + "%");
}
foreach (string file in Directory.GetFi les(dirs[i])) {
Console.WriteLi ne(file);
}
}
return 0;
} catch (Exception ex) {
Console.Error.W riteLine(ex.Mes sage);
return -1;
}
}
}

(winform)

using System;
using System.Windows. Forms;
using System.Componen tModel;
using System.Diagnost ics;
using System.IO;
using System.Text.Reg ularExpressions ;

class SomeForm : Form {
static void Main() {
Application.Ena bleVisualStyles ();
using (Form f = new SomeForm()) {
Application.Run (f);
}
}

Button goStop;
BackgroundWorke r worker;
const string BUTTON_TEXT = "Go";
protected override void OnLoad(EventArg s e) {
base.OnLoad(e);
goStop = new Button();
goStop.Text = BUTTON_TEXT;
goStop.Click += new EventHandler(go Stop_Click);
Controls.Add(go Stop);
worker = new BackgroundWorke r();
worker.WorkerSu pportsCancellat ion = true;
worker.WorkerRe portsProgress = true;
worker.DoWork+= new DoWorkEventHand ler(worker_DoWo rk);
worker.Progress Changed += new
ProgressChanged EventHandler(wo rker_ProgressCh anged);
worker.RunWorke rCompleted += new
RunWorkerComple tedEventHandler (worker_RunWork erCompleted);
}

void worker_RunWorke rCompleted(obje ct sender,
RunWorkerComple tedEventArgs e) {
goStop.Text = BUTTON_TEXT;
if (e.Cancelled) {
this.Text = "cancelled" ;
} else if ((int) e.Result == 0) {
this.Text = "complete";
} else {
this.Text = "error " + e.Result.ToStri ng();
}
}

void worker_Progress Changed(object sender,
ProgressChanged EventArgs e) {
goStop.Text = e.ProgressPerce ntage.ToString( ) + "%";
}

void goStop_Click(ob ject sender, EventArgs e) {
if (worker.IsBusy) {
worker.CancelAs ync();
} else {
worker.RunWorke rAsync();
}
}

void worker_DoWork(o bject sender, DoWorkEventArgs e)
{
string exe = @"c:\walker.exe ", root = @"c:\develop\t" ;
ProcessStartInf o psi = new ProcessStartInf o(exe, root);
psi.UseShellExe cute = false;
psi.RedirectSta ndardOutput = true;
psi.CreateNoWin dow = true;
using(Process proc = Process.Start(p si))
using(StreamRea der reader = proc.StandardOu tput) {
worker.ReportPr ogress(0);
Regex re = new Regex(@"\d{1,3} %");
int index = 0;
while (!reader.EndOfS tream) {
if (worker.Cancell ationPending) {
proc.Kill();
e.Cancel = true;
break;
}
string line = reader.ReadLine ();
if (re.IsMatch(lin e)) {

worker.ReportPr ogress(int.Pars e(line.TrimEnd( '%')));
} else {
if (index++ % 20 == 0) {
this.Invoke((Me thodInvoker)del egate {
this.Text = line;
});
}
}
}
if (!e.Cancel) {
e.Result = proc.ExitCode;
}

}
}
}

[Alistair George]

Re: Console app async control

Marc Gravell wrote:

>
I'll put an example together if you like...
>
Marc
>

Thank you so much Marc. You have made the task very easy for me to
implement. On the few google results that I have read on the subject, it
is indicated that getting the output from the CMD window is unreliable
to say the least. This is a problem that the previous implimentation
had. So it will be interesting to see how well it works if you like I
will stay in touch.

Am trying to improve a situation whereby the previous method used to
occasionally hang when they used the cmd output. I am not sure whether
they used sync or async comms in that case.
Thanks again, Al.

[Marc Gravell]

Re: Console app async control

I did some more playing with this, and it looks like (irritatingly) in
the event of a hang, the Begin... approach is more stable... sorry to
confuse things! I'll see if I can get that working...

Marc

[Alistair George]

Re: Console app async control

Marc Gravell wrote:

I did some more playing with this, and it looks like (irritatingly) in
the event of a hang, the Begin... approach is more stable... sorry to
confuse things! I'll see if I can get that working...
>
Marc
>

OK, but are you saying that the method can hang due to comms problems?

[Chris Dunaway]

Re: Console app async control

On Sep 10, 2:25 pm, Alistair George <non...@xtra.co .nzwrote:

Marc Gravell wrote:

I did some more playing with this, and it looks like (irritatingly) in
the event of a hang, the Begin... approach is more stable... sorry to
confuse things! I'll see if I can get that working...

>

Marc

>
OK, but are you saying that the method can hang due to comms problems?

Be careful when redirecting both standard output and standard error as
there can be a deadlock issue. Check the docs which give some more
details about this issue.

Chris

[Alistair George]

Re: Console app async control

Chris Dunaway wrote:

On Sep 10, 2:25 pm, Alistair George <non...@xtra.co .nzwrote:

>Marc Gravell wrote:

>>I did some more playing with this, and it looks like (irritatingly) in
>>the event of a hang, the Begin... approach is more stable... sorry to
>>confuse things! I'll see if I can get that working...
>>Marc

>OK, but are you saying that the method can hang due to comms problems?

>
Be careful when redirecting both standard output and standard error as
there can be a deadlock issue. Check the docs which give some more
details about this issue.
>
Chris
>

Thanks Chris.
Mark did you want to go any further or shall I proceed with caution
using the code that you promulgated?
Cheers,
Alistair.