[2.0] Best Way to Handle Command-Line Arguments

[penagate]

Hi all,

Suppose I want my executable to accept the following argument format:

exename -arg1 val1 -arg2 val2

where the arguments may be in any order; some required, some optional.

Currently I am using the args parameter of the Main method, joining it into a string, and using regular expressions to get the -k v pairs. This is rather ugly.
I'd like to know if there is a neater way of handling this.

Cheers

- P

[jmcilhinney]

Let's assume that your app has three valid command line arguments: -a and -b that also require a value and -c that doesn't. I'd be inclined to do something like this:

private void Form1_Load(object sender, EventArgs e)
{
	string[] args = Environment.GetCommandLineArgs();
	int index = 0;

	do
	{
		switch (args[index])
		{
			case "-a":
				index++;
				// Call a method to process the arg at index.
				break;
			case "-b":
				index++;
				// Call a method to process the arg at index.
				break;
			case "-c":
				// Do whatever is appropriate.
				break;
			default:
				break;
		}

		index++;
	} while (index < args.Length);
}

If you wanted to ensure that each argument was not processed more than once then you could add a bit of validation:

private void Form1_Load(object sender, EventArgs e)
{
	string[] args = Environment.GetCommandLineArgs();
	List<string> processed = new List<string>();
	int index = 0;

	do
	{
		switch (args[index])
		{
			case "-a":
				index++;

				if (index < args.Length && !processed.Contains("-a"))
				{
					// Call a method to process the arg at index.
					processed.Add("-a");
				}

				break;
			case "-b":
				index++;

				if (index < args.Length && !processed.Contains("-b"))
				{
					// Call a method to process the arg at index.
					processed.Add("-b");
				}

				break;
			case "-c":
				if (!processed.Contains("-c"))
				{
					// Do whatever is appropriate.
					processed.Add("-c");
				}

				break;
			default:
				break;
		}

		index++;
	} while (index < args.Length);
}

The code may be a bit lengthy but it is clear. Note that that will also just ignore invalid arguments. You might choose to notify the user of the error instead.

[penagate]

Cheers, that looks a lot neater.

Here's (roughly) what I used:

while (index < args.Length - 1)
{
  switch (args[index++])
  {
    case "-a":
      if (a == null)
        a = args[index++];

      break;

    // etc.

    default:
      break;
  }
}