Tutorial :Passing command-line arguments in C#


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?


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  


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.


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].


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"


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?"


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;  }  


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;                  }              }  


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.

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