How to check the arguments with Regex?

Question

I'm stuck with regular expressions. The program is a console application written in C#. There are a few commands. I want to check the arguments are right first. I thought it'll be easy with Regex but couldn't do that:

var strArgs = "";

foreach (var x in args)
{
    strArgs += x + " ";
}
if (!Regex.IsMatch(strArgs, @"(-\?|-help|-c|-continuous|-l|-log|-ip|)* .{1,}"))
{
    Console.WriteLine("Command arrangement is wrong. Use \"-?\" or \"-help\" to see help.");
    return;
}

Usage is:

program.exe [-options] [domains]

The problem is, program accepts all commands. Also I need to check "-" prefixed commands are before the domains. I think the problem is not difficult to solve.

Thanks...

wow, and to think I just use a switch cos it's easier for me to code and maintain :\ — jcolebrand, Sep 09 '10 at 15:01

score 4 · Accepted Answer · answered Sep 09 '10 at 15:08

Since you will end up writing a switch statement to process the options anyway, you would be better off doing the checking there:

switch(args[i])
{
case "-?": ...
case "-help": ...
...
default:
  if (args[i][0] == '-')
    throw new Exception("Unrecognised option: " + args[i]);
}

score 2 · Answer 2 · edited May 23 '17 at 12:11

First, to parse command line arguments don't use regular expressions. Here is a related question that I think you should look at:

Best way to parse command line arguments in C#?

But for your specific problem with your regular expression - the options are optional and then you match against a space followed by anything at all, where anything can include for example invalid domains and/or invalid options. So far example this is valid according to your regular expression:

program.exe -c -invalid

One way to improve this by being more precise about the allowed characters in a domain rather than just matching anything.

Another problem with your regular expressions is that you don't allow spaces between the switches. To handle that you probably want something like this:

(?:(?:-\?|-help|-c|-continuous|-l|-log|-ip) +)*

I'd also like to point out that you should use string.Join instead of the loop you are currently using.

string strArgs = string.Join(" ", args);

score 1 · Answer 3 · answered Sep 09 '10 at 15:14

1

Don't reinvent the wheel, handling command line arguments is a solved problem.

I've gotten good use out of the Command Line Parser Library for .Net.

answered Sep 09 '10 at 15:14

quentin-starin

26,121
7
68
86

I've never actually seen that library, but I like the idea. Thanks for sharing. Now I have a good library to goto for attributes examples too when I want to explain them to someone ;) – jcolebrand Sep 09 '10 at 15:28

Bernd · Answer 4 · 2010-09-09T20:45:53.530

0

Actually the easiest way to achieve command line argument parsing is to create a powershell commandlet. That gives you a really nice way to work with arguments.

edited Sep 09 '10 at 20:45

answered Sep 09 '10 at 15:23

Bernd

539
3
10

score 0 · Answer 5 · answered Feb 03 '11 at 03:01

I have been using this function with success... perhaps it will be useful for someone else...

First, define your variables:

private string myVariable1;
private string myVariable2;
private Boolean debugEnabled = false;

Then, execute the function:

loadArgs();

and add the function to your code:

    private void loadArgs()
    {
        const string namedArgsPattern = "^(/|-)(?<name>\\w+)(?:\\:(?<value>.+)$|\\:$|$)";
        System.Text.RegularExpressions.Regex argRegEx = new System.Text.RegularExpressions.Regex(namedArgsPattern, System.Text.RegularExpressions.RegexOptions.Compiled);
        foreach (string arg in Environment.GetCommandLineArgs())
        {
            System.Text.RegularExpressions.Match namedArg = argRegEx.Match(arg);
            if (namedArg.Success)
            {
                switch (namedArg.Groups["name"].ToString().ToLower())
                {
                    case "myArg1":
                        myVariable1 = namedArg.Groups["value"].ToString();
                        break;
                    case "myArg2":
                        myVariable2 = namedArg.Groups["value"].ToString();
                        break;
                    case "debug":
                        debugEnabled = true;
                        break;
                    default:
                        break;
                }
            }
        }
    }

and to use it you can use the command syntax with either a forward slash "/" or a dash "-":

myappname.exe /myArg1:Hello /myArg2:Chris -debug

score 0 · Answer 6 · answered Jul 22 '21 at 10:28

This regex parses the command line arguments into matches and groups so that you can build a parser based on this regex.

((?:|^\b|\s+)--(?<option_1>.+?)(?:\s|=|$)(?!-)(?<value_1>[\"\'].+?[\"\']|.+?(?:\s|$))?|(?:|^\b)-(?<option_2>.)(?:\s|=|$)(?!-)(?<value_2>[\"\'].+?[\"\']|.+?(?:\s|$))?|(?<arg>[\"\'].+?[\"\']|.+?(?:\s|$)))

This Regex will parse the Following and works in almost all the languages

--in-argument hello --out-stdout false positional -x
--in-argument 'hello world"
"filename"
--in-argument="hello world'
--in-argument='hello'
--in-argument hello
"hello"
helloworld
--flag-off
-v
-x="hello"
-u positive
C:\serverfile
--in-arg1='abc' --in-arg2=hello world c:\\test

Try on Regex101

How to check the arguments with Regex?

6 Answers6