How can I modify this to work with any regex with capture groups?-CodePudding

Because I used named groups in the following code it only works with a specific regex. How can I modify it to take any regex and output all capture groups as csv?

            try
            {
                rg = new Regex(@arguments.Regex, RegexOptions.Compiled | RegexOptions.IgnoreCase);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            StringBuilder sb = new StringBuilder();
            foreach (string line in System.IO.File.ReadLines(@arguments.FilePath))
            //audit.log
            {
                var loginMatch = rg.Match(line);
                if(!loginMatch.Groups["username"].Value.Equals(""))
                {
                sb.Append($"{loginMatch.Groups["username"].Value},{loginMatch.Groups["time"].Value},");
                }
            }
            Console.Out.WriteLine(sb.ToString());```
Thanks!

CodePudding user response：

Enumerate loginMatch.Groups using a loop or LINQ, for example

for(int i = 1; i < loginMatch.Groups.Count; i  )
  sb.Append($"{g[i].Value},");
sb.Length--; //trim off last comma
sb.AppendLine();

sb.AppendLine(string.Join(",", loginMatch.Groups.Cast<Group>().Skip(1).Select(g => g.Value)));

Given that Group.ToString() also returns the value, I suspect these could be simplified some too, e.g...

for(int i = 1; i < loginMatch.Groups.Count; i  )
  sb.Append(g[i]).Append(",");

plus the trim/newline, or

string.Join(",", loginMatch.Groups.Cast<Group>().Skip(1));

plus the sb bit

If you've named some groups but not others, and you don't know what the names are, but you only want to put the named ones in the CSV, turn on RegexOptions.ExplicitCapture and remove the Skip/set the loop to start from 0. The Skip/1 is there to avoid including the default capture (the input) in the file, but if you have only explicit captures there won't be a default group so your captures will start from 0

Totally agree with Enigmativity's comment; use a CSV writer library, or make this code more involved with regards to escaping commas in the data etc.. I didn't add that complexity to the post because I'm specifically addressing the query of how to enumerate capturing groups

CodePudding user response：

A regular expression (shortened as regex or regexp;[1] also referred to as rational expression[2][3]) is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation. It is a technique developed in theoretical computer science and formal language theory.