[C#] Output command line app progress bar to textbox on one line

[DPyro]

I got a program that I'd like to output to a textbox but I'm having an issue with the progress bar. All the stdout from the app displays correctly except once I get to a progress bar:

00
00
00
01
01
01
02
02
02
etc...
[/CODE]

I made this code to handle it:

[CODE]
string o = "";
string pattern = @"(\d{1,2}\%)";
Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);
while (!process.HasExited)
{
StringBuilder output = new StringBuilder(process.StandardOutput.ReadLine());
MatchCollection matches = rgx.Matches(o);
if (output.ToString () != o){
if (matches.Count > 0)
{
this.txtOutputLog.AppendText(output + System.Environment.NewLine);
}
else
{
this.txtOutputLog.AppendText(output + System.Environment.NewLine);
}
Application.DoEvents();
}
o = output.ToString();
}
[/CODE]

but still get this:

[CODE]
01
02
03
04
05
[/CODE]

How can I get the progress bar to print on one line? I've also tried using "\r".

[Andre S. Veteran]

AppendText, as its name suggests, adds text after whatever existing text is already there. What you're trying to do if I understand well is to replace existing text (the progress indicator) with new text. For this purpose, you could take the existing text, extract everything but the last 2 characters (with String.Substring), add the 2 replacement characters to the resulting string, and set the textbox's Text value to this new string.

[DPyro]

Right, I was using AppendText to read the output in real time, line by line. I didn't know what code to use to replace the last line (progress bar). I can get a progress bar on the one line but need to keep all the other output as well.

ie. simple setting this.txtOutputLog.Text = (output); works but won't keep the previous output.

this.txtOutputLog.Text += (output); looks weird and also setting this.txtOutputLog.Text += messes with the textbox focus.

[paxa]

what about removing the newline? in the if and else?

[DPyro]

  On 13/04/2013 at 00:13, paxa said:

what about removing the newline? in the if and else?

Makes it look like this:

00% 01% 02% 03% 04% 05% 06%

[Andre S. Veteran]

something like

txtbox.Text = txtbox.Text.Substring(0, txtbox.Text.Length - 2);
txtbox.AppendText(newCounterValue);
[/CODE]

Substring allows to select which part of a string you want, you can use it to select everything except the characters you want to replace and add the replacement characters after that.

[DPyro]

  On 13/04/2013 at 00:37, Dr_Asik said:

something like

txtbox.Text = txtbox.Text.Substring(0, txtbox.Text.Length - 2);
txtbox.AppendText(newCounterValue);
[/CODE]

Substring allows to select which part of a string you want, you can use it to select everything except the characters you want to replace and add the replacement characters after that.

This seems to work OK

[CODE]
this.txtOutputLog.Text = this.txtOutputLog.Text.Substring(0, this.txtOutputLog.Text.Length - 11);
this.txtOutputLog.AppendText(o);
[/CODE]

Textbox seems to flicker slightly...

[Andre S. Veteran]

If you're really concerned about how the progress report looks you should probably be using a real ProgressBar instead. :p

[DPyro]

Ya I was thinking about doing that but would need to figure out how to add the background worker etc.

[Andre S. Veteran]

You don't need a background worker to use a progress bar any more than to use a textbox. What you need a background worker for is having your long-running operation not block the UI thread so the application remains responsive.

[firey]

  On 13/04/2013 at 01:03, DPyro said:

Ya I was thinking about doing that but would need to figure out how to add the background worker etc.

Could just use the Application.DoEvents() function to do your updates to a progress bar without a background worker. This will stop the gui from locking, but you won't need to use a Background worker.. which is really just a thread with training wheels.

[Andre S. Veteran]

  On 13/04/2013 at 01:16, firey said:

Could just use the Application.DoEvents() function to do your updates to a progress bar without a background worker. This will stop the gui from locking, but you won't need to use a Background worker.. which is really just a thread with training wheels.

With easy options like BackgroundWorker (.NET 2) and async in C# (C# 5) now there's really no reason to use DoEvents() anymore, which is an error-prone hack. It may be easy to write, but it's hell to debug. The UI thread is for the UI, using it to perform long-running operations is just bad design.

[DPyro]

Ok, while this works for one application. It doesn't work in another which outputs something like this:

0% 0/50000

1% 500/50000

3% 1500/50000

Think I need a better way to read stdout...

[Andre S. Veteran]

This is all just standard string manipulation, I suggest you take a look at the String class, specifically methods like Trim, Substring, Replace, Concat, Join and Split. For instance here you could store the last entry you added in a temporary string and do a Replace of that with the new one you want. Or you could split by newline characters, exclude the last line, join the result and add the replacement at the end. There are many ways to go about this.

[firey]

  On 13/04/2013 at 01:29, Dr_Asik said:

With easy options like BackgroundWorker (.NET 2) and async in C# (C# 5) now there's really no reason to use DoEvents() anymore, which is an error-prone hack. It may be easy to write, but it's hell to debug. The UI thread is for the UI, using it to perform long-running operations is just bad design.

While I agree with that, it would be a working hack he could use without learning bw's and async stuff.

[Eric Veteran]

TextBox isn't a very good control to use for console output. It looks like what you're trying to do is simulate a console to display the output from a CLI application you're running in a process. I would recommend using a ListBox instead. You can use the ListBox.Items.Add() method to add each line as it's output then when you get to your progress parsing you can use

ListBox.Items[ListBox.Items.Count - 1] = "<whatever you want>";

to replace the line with the new value. Then only that particular line might flicker. :)

Your second problem is a regular expression issue. If the CLI app's output is different you'd have to match it differently as well. Match(@"(\d+)%.*" ) should get you just the percentage number from your example.

[DPyro]

Ok the listbox works good but as you said it does flicker quite a bit.

EDIT:

I added this to select the last line which gets rid of the flicker, but how do I change the selected color so that you can't tell it's selected

lstOutputLog.SelectedIndex = lstOutputLog.Items.Count - 1;
[/CODE]

Edited April 13, 2013 by DPyro

[DPyro]

Should be clear that I'm replacing:

lstOutputLog.Refresh();
[/CODE]

With:

[CODE]
lstOutputLog.SelectedIndex = lstOutputLog.Items.Count - 1;
[/CODE]

Unless there's a better way to update the listbox after each line is added...

[Eric Veteran]

You don't need to select anything. You can just change the last line in the Listbox with the code I posted. It will make the last line say "<whatever you want>" the way it is so you would want to use the percentage that you parsed from the process's output instead of the example string. After it doesn't match anymore (i.e.: the process is complete) you can continue logging whatever else it might print using the listbox's Add() method.

[DPyro]

  On 14/04/2013 at 03:05, GreyWolf said:

You don't need to select anything. You can just change the last line in the Listbox with the code I posted. It will make the last line say "<whatever you want>" the way it is so you would want to use the percentage that you parsed from the process's output instead of the example string. After it doesn't match anymore (i.e.: the process is complete) you can continue logging whatever else it might print using the listbox's Add() method.

This is what I have, but if I don't refresh the listbox somehow then nothing is displayed until the process has ended.

while (!process.HasExited)
{
	string pattern = @"(\d+)%.*";
	Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);
	StringBuilder output = new StringBuilder(process.StandardOutput.ReadLine());
	Match Match = rgx.Match(output.ToString ());
	if (!Match.Success)
	{
         lstOutputLog.Items.Add(output + "\n");
	}
	else
	{
         lstOutputLog.Items[lstOutputLog.Items.Count - 1] = (output);
	}
}
[/CODE]

The other issue I'm having is that the output freezes every couple of seconds. Think it has something to do with the buffer being filled up and waiting to be flushed. :/

[DPyro]

  On 14/04/2013 at 05:41, DPyro said:

The other issue I'm having is that the output freezes every couple of seconds. Think it has something to do with the buffer being filled up and waiting to be flushed. :/

So I added this to the cli program which is written in c/c++, which fixes the freezing of stdout

setvbuf(stdout, NULL, _IONBF, 0);
[/CODE]

Only issue I have is that I have to set

[CODE]lstOutputLog.SelectionMode = SelectionMode.One;[/CODE]

at the beginning and

[CODE]lstOutputLog.SelectionMode = SelectionMode.None;[/CODE]

at the end so that the listbox isn't selectable. At the end of program run, the log scrolls back to the top :wacko:

[Andre S. Veteran]

  On 14/04/2013 at 05:41, DPyro said:

This is what I have, but if I don't refresh the listbox somehow then nothing is displayed until the process has ended.

That's normal, because you're keeping the UI thread busy doing your loop, it cannot do anything else during that. It cannot even repaint itself. That's why the UI thread is for updating the UI and responding to user events, not performing your long-running computations.

There are different ways to go about fixing this. The classical, most correct way is to spawn a background thread; there many tutorials with full code on how to do this, example: this.

Alternatively, you could still do this on the UI thread, but one small part at a time, for instance by passing what forms the body of your while loop to a timer. This will cause this code to execute repeatedly, but will let the UI execute as it wishes between each two calls.

There's as also, as firey pointed out, a hack that consists of calling Application.DoEvents() in your loop; this effectively triggers a full UI update from the currently executing UI update; as long it doesn't end up calling back into your code, it shouldn't lead to horrifying things. Note the use of conditionals there; this isn't a reliable way, which can cause your app to randomly behave in ways you don't understand. I don't recommend this approach unless you really know what you're doing (and if you did you'd probably never choose this approach).