Passing command-line arguments in C#

Question

I'm trying to pass command-line arguments to a C# application, but I have problem passing something like this

"C:\Documents and Settings\All Users\Start Menu\Programs\App name"

even if I add " " to the argument.

Here is my code:

    public ObjectModel(String[] args)
    {
        if (args.Length == 0) return; //no command line arg.
        //System.Windows.Forms.MessageBox.Show(args.Length.ToString());
        //System.Windows.Forms.MessageBox.Show(args[0]);
        //System.Windows.Forms.MessageBox.Show(args[1]);
        //System.Windows.Forms.MessageBox.Show(args[2]);
        //System.Windows.Forms.MessageBox.Show(args[3]);
        if (args.Length == 3)
        {
            try
            {
                RemoveInstalledFolder(args[0]);
                RemoveUserAccount(args[1]);
                RemoveShortCutFolder(args[2]);
                RemoveRegistryEntry();
            }
            catch (Exception e)
            {
            }
        }
        }

And here is what I'm passing:

C:\WINDOWS\Uninstaller.exe  "C:\Program Files\Application name\"  "username"  "C:\Documents and Settings\All Users\Start Menu\Programs\application name"

The problem is I can get the first and the second args correctly, but the last one it gets as C:\Documents.

Any help?

Answer 1

What exactly is the problem? Anyway here's some general advice:

Make sure your Main method (in Program.cs) is defined as:

void Main(string[] args)

Then args is an array containing the command-line arguments.

Answer 2

I noticed the same annoying issue recently, and decided to write a parser to parse the command line arguments array out myself.

Note: the issue is that the .NET CommandLine Arguments passed to the static void Main(string[] args) function escapes \" and \\. This is by design, since you may actually want to pass an argument that has a quote or backslash in it. One example:

say you wanted to pass the following as a single argument:

-msg:Hey, "Where you at?"

eg.

sampleapp -msg:"Hey, \"Where you at?\""

Would be how to send it with the default behavior.

If you don't see a reason for anyone to have to escape quotes or backslashes for your program, you could utilize your own parser to parse the command line, as below.

IE. [program].exe "C:\test\" arg1 arg2

would have a args[0] = c:\test" arg1 arg2

What you would expect is args[0]=c:\test\ and then args[1]=arg1 and args[2]=arg2.

The below function parses the arguments into a list with this simplified behavior.

Note, arg[0] is the program name using the below code. (You call List.ToArray() to convert the resulting list to a string array.)

protected enum enumParseState : int { StartToken, InQuote, InToken };
public static List<String> ManuallyParseCommandLine()
{
    String CommandLineArgs = Environment.CommandLine.ToString();

    Console.WriteLine("Command entered: " + CommandLineArgs);

    List<String> listArgs = new List<String>();

    Regex rWhiteSpace = new Regex("[\\s]");
    StringBuilder token = new StringBuilder();
    enumParseState eps = enumParseState.StartToken;

    for (int i = 0; i < CommandLineArgs.Length; i++)
    {
        char c = CommandLineArgs[i];
    //    Console.WriteLine(c.ToString()  + ", " + eps);
        //Looking for beginning of next token
        if (eps == enumParseState.StartToken)
        {
            if (rWhiteSpace.IsMatch(c.ToString()))
            {
                //Skip whitespace
            }
            else
            {
                token.Append(c);
                eps = enumParseState.InToken;
            }


        }
        else if (eps == enumParseState.InToken)
        {
            if (rWhiteSpace.IsMatch(c.ToString()))
            {
                Console.WriteLine("Token: [" + token.ToString() + "]");
                listArgs.Add(token.ToString().Trim());
                eps = enumParseState.StartToken;

                //Start new token.
                token.Remove(0, token.Length);
            }
            else if (c == '"')
            {
               // token.Append(c);
                eps = enumParseState.InQuote;
            }
            else
            {
                token.Append(c);
                eps = enumParseState.InToken;
            }

        }
            //When in a quote, white space is included in the token
        else if (eps == enumParseState.InQuote)
        {
            if (c == '"')
            {
               // token.Append(c);
                eps = enumParseState.InToken;
            }
            else
            {
                token.Append(c);
                eps = enumParseState.InQuote;
            }

        }


    }
    if (token.ToString() != "")
    {
        listArgs.Add(token.ToString());
        Console.WriteLine("Final Token: " + token.ToString());
    }
    return listArgs;
}

Answer 3

To add Ian Kemp's answer

If you assembly is called "myProg.exe" and you pass in the string "C:\Documents and Settings\All Users\Start Menu\Programs\App name" link so

C:\>myprog.exe "C:\Documents and Settings\All Users\Start Menu\Programs\App name"

the string "C:\Documents and Settings\All Users\Start Menu\Programs\App name"

will be at args[0].

Answer 4

In response to WWC's answer, Jamezor commented that his code will fail if the first character is a quote.

To fix that problem, you can replace the StartToken case with this:

            if (eps == enumParseState.StartToken)
            {
                if (rWhiteSpace.IsMatch(c.ToString()))
                {
                    //Skip whitespace
                }
                else if (c == '"')
                {
                    eps = enumParseState.InQuote;
                }
                else
                {
                    token.Append(c);
                    eps = enumParseState.InToken;
                }
            }

Answer 5

To add to what everyone else has already said, It might be an escaping problem. You should escape your backslashes by another backslash.

Should be something like:

C:\>myprog.exe "C:\\Documents and Settings\\All Users\\Start Menu\\Programs\\App name"

Answer 6

I just ran a check and verified the problem. It surprised me, but it is the last \ in the first argument.

"C:\Program Files\Application name\" <== remove the last '\'

This needs more explanation, does anybody have an idea? I'm inclined to call it a bug.

---

Part 2, I ran a few more tests and

"X:\\aa aa\\" "X:\\aa aa\" next

becomes

X:\\aa aa\
X:\\aa aa" next

A little Google action gives some insight from a blog by Jon Galloway, the basic rules are:

• the backslash is the escape character
• always escape quotes
• only escape backslashes when they precede a quote.