Parsing command line parameters

Question

Hi all,

I am using VB 2010 to develop a console app which accepts parameters using the following format:

cmd1=value1<sp>cmd2=value2...

If my app accepts these parameters:

s - source folder specification

f - binary representation of flags

Then a valid command line could be

MyConAppEXE s=c:\work f=10001

I have the following code to parse the command line:

    Dim fields() As String
    Using ms As New System.IO.MemoryStream(System.Text.Encoding.Default.GetBytes(Environment.CommandLine))
      Using parser As New Microsoft.VisualBasic.FileIO.TextFieldParser(ms, System.Text.Encoding.Default)
        parser.SetDelimiters(" ", "=")
        parser.HasFieldsEnclosedInQuotes = True
        fields = parser.ReadFields
      End Using
    End Using

The above produces an array in the following format:

(0) Executable path & name

(1) First switch

(2) First value

(3) Second switch

(4) Second value

And so on. The issue I have is that when the app is run without any parameters it produces the following array:

(0) Executable path & name

(1) Empty string

Although not a deal breaker, it is a bit of a nuisance having to test for 1 or 2 elements to determine whether no parameters were passed. I've tried determining why the parse code creates this empty element, but I have not been successful. As a kluge I tried scanning the array from last to first element with a FOR loop and removing the empty element by using a redim preserve statement but this does not work. The code does not produce any kind of error or message but when I check the array's length it still is 2 even though in theory it should be 1. Here is that code, just for completeness, although I would be looking for a better solution (if there is one):

    'Scan the array to eliminate empty elements.
    For i As Integer = fields.Length - 1 To 0 Step -1
      'If this element is blank/empty eliminate it.
      If fields(i).Trim.Length() = 0 Then
        ReDim Preserve fields(fields.Length() - 1)
      End If
    Next i

Another attempt I made was setting the TrimWhiteSpace property to True without any difference in the outcome.

Does anyone have any remarks or suggestions? Perhaps a better way of doing the parsing or how to eliminate the empty array element, if at all possible. As usual, thank you for your time and assistance. Saga

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Insanity is the prelude to discovery

Answer 1

I'm not sure what the issue is.

1. I tested the code in a WinForm app. I launched the WinForm app using the command prompt and the label displayed the count for the array as 1. Then I launched the same app using the Run application which I did after I created the following image. The count for the array became 2 for some reason.

2. I created a console app with the code. I launched the console app using the command prompt. I never saw the console app launch but for some reason the number 1 displayed on the next line of the command prompt app. Maybe when a command prompt is running and a console app is launched by it then it becomes the console app or something weird. I'm not familiar with console apps. Anyhow I then launched the console app with the Run application like in the bottom pic in the image below and the number 2 appeared for the count of the array.

So I've zero idea why launching an app using the command prompt is different then when using the Run application.

Also when I use task manager it shows Run as an app running on my desktop when I launch Run but when I right click on it and go to process task manager shows it as explorer.exe/Windows Explorer. And if I execute the console app by clicking on it when it is displayed in Windows Explorer a 2 is displayed for the arrays count again.

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Hello. I'm old and retired. I like to program if you could call what I do programming. However I'd like to code for you! If you've got the dime then I've got the time. Call me, landline, @ BR-549.

Answer 2

The issue I have is that when the app is run without any parameters it produces the following array:

(0) Executable path & name
(1) Empty string

Probably the simplest test for this case is

        If My.Application.CommandLineArgs.Count > 0 Then ...

Certainly that is simpler than any code that processes the array.

   

Answer 3

First of, thanks for giving this issue time. I did all my testing in the IDE. I am going to build a small test app like you did, buld it and test from there. Yeah, it is very unusual and would like to do more research and experimenting before I move on. I'll post any worthwhile findings here. Saga

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Insanity is the prelude to discovery

Answer 4

This is very interesting. Yes, if I check whether there are any parameters to begin with I can ether go ahead and get if there are or simply return a more indicative data structure. Let me look at this further and will follow up. Thanks! Saga

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Insanity is the prelude to discovery

Answer 5

Haha,

 I already ran into this.

The reason in simple, Windows add a space after the file name ... 

so, just  Trim the string and you won't have this empty field anymore:

 ....GetBytes(Environment.CommandLine.Trim))

Answer 6

Haha,

 I already ran into this.

The reason in simple, Windows add a space after the file name ... 

so, just  Trim the string and you won't have this empty field anymore:

 ....GetBytes(Environment.CommandLine.Trim))

Man CP. That's really so simple it's funny!

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Hello. I'm old and retired. I like to program if you could call what I do programming. However I'd like to code for you! If you've got the dime then I've got the time. Call me, landline, @ BR-549.

Answer 7

Ouch! Now I can't wait till Monday to get to the office to try this. Saga

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Insanity is the prelude to discovery

Answer 8

Crazypennie, thanks again. For my given situation yours was the most practical solution.

I will also keep Acamar's solution in mind as it makes sense to test whether there are any switches provided even before I go ahead and attempt to process them with code. Saga

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Insanity is the prelude to discovery