Command Line Flags in Visual Basic .NET

Here’s the translation of the Go code to Visual Basic .NET, along with explanations in Markdown format suitable for Hugo:

Command-line flags are a common way to specify options for command-line programs. For example, in wc -l the -l is a command-line flag.

Visual Basic .NET provides built-in support for parsing command-line arguments. We’ll use this functionality to implement our example command-line program.

Imports System

Module CommandLineFlags
    Sub Main(args As String())
        ' Basic flag declarations are available through the My.Application.CommandLineArgs collection
        ' We'll use a simple parser to handle flags and their values

        Dim word As String = "foo"
        Dim numb As Integer = 42
        Dim fork As Boolean = False
        Dim svar As String = "bar"

        ' Parse command-line arguments
        For i As Integer = 0 To args.Length - 1
            Select Case args(i)
                Case "-word"
                    If i + 1 < args.Length Then
                        word = args(i + 1)
                        i += 1
                    End If
                Case "-numb"
                    If i + 1 < args.Length AndAlso Integer.TryParse(args(i + 1), numb) Then
                        i += 1
                    End If
                Case "-fork"
                    fork = True
                Case "-svar"
                    If i + 1 < args.Length Then
                        svar = args(i + 1)
                        i += 1
                    End If
            End Select
        Next

        ' Print the parsed options and any trailing positional arguments
        Console.WriteLine("word: " & word)
        Console.WriteLine("numb: " & numb)
        Console.WriteLine("fork: " & fork)
        Console.WriteLine("svar: " & svar)
        Console.WriteLine("tail: " & String.Join(" ", args.Skip(Array.FindLastIndex(args, Function(a) a.StartsWith("-")) + 2)))
    End Sub
End Module

To experiment with the command-line flags program, it’s best to first compile it and then run the resulting executable directly.

$ vbc CommandLineFlags.vb

Try out the built program by first giving it values for all flags.

$ CommandLineFlags.exe -word opt -numb 7 -fork -svar flag
word: opt
numb: 7
fork: True
svar: flag
tail:

Note that if you omit flags, they automatically take their default values.

$ CommandLineFlags.exe -word opt
word: opt
numb: 42
fork: False
svar: bar
tail:

Trailing positional arguments can be provided after any flags.

$ CommandLineFlags.exe -word opt a1 a2 a3
word: opt
...
tail: a1 a2 a3

Unlike the Go flag package, this simple implementation doesn’t automatically generate help text or handle errors for undefined flags. You would need to implement these features manually if required.

To add help text, you could check for a -h or --help flag and print usage information:

If args.Contains("-h") OrElse args.Contains("--help") Then
    Console.WriteLine("Usage of CommandLineFlags:")
    Console.WriteLine("  -word <value>: a string (default: foo)")
    Console.WriteLine("  -numb <value>: an integer (default: 42)")
    Console.WriteLine("  -fork: a boolean flag")
    Console.WriteLine("  -svar <value>: a string variable (default: bar)")
    Environment.Exit(0)
End If

This implementation provides similar functionality to the Go example, but uses Visual Basic .NET’s built-in features and syntax. The command-line argument parsing is done manually, as Visual Basic .NET doesn’t have a direct equivalent to Go’s flag package.

Command Line Arguments in Visual Basic .NET

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Command Line Flags in Visual Basic .NET