Regex help: My regex pattern will match invalid strings

Question

Hello!

i really like Regex, unfortantly Im not that good at it yet. So therfore I hope you guys can help me out.

The text string I want to validate consists of what I call "segments". A single segment might look like this:

 [A-Z,S,3]

So far I managed to build this regex pattern

(?:\[(?<segment>[^,\]\[}' ]+?,[S|D],\d{1})\])+?

it works but it will return matches even though the whole text string contains invalid text. I guess I need to use ^ and $ somewhere in my pattern but I can't figure out how!?

I would like my pattern to produce the following results:

• [A-Z,S,3][A-Za-z0-9åäöÅÄÖ,D,4] OK(two segments)
• [A-Z,S,3]aaaa[A-Za-z0-9åäöÅÄÖ,D,4] No match
• crap[A-Z,S,3][A-Za-z0-9åäöÅÄÖ,D,4] No match
• [A-Z,S,3][] No match
• [A-Z,S,3][klm,D,4][0-9,S,1] OK(three segments)

Answer 1

You want something like this:

/^(\[[^],]+,[SD],\d\])+$/

Here is an example of how you could use this regular expression in C#:

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string[] tests = {
            "[A-Z,S,3][A-Za-z0-9,D,4]",
            "[A-Z,S,3]aaaa[A-Za-z0-9,D,4]",
            "crap[A-Z,S,3][A-Za-z0-9,D,4]",
            "[A-Z,S,3][]",
            "[A-Z,S,3][klm,D,4][0-9,S,1]"
        };

        string segmentRegex = @"\[([^],]+,[SD],\d)\]";
        string lineRegex = "^(" + segmentRegex + ")+$";

        foreach (string test in tests)
        {
            bool isMatch = Regex.Match(test, lineRegex).Success;
            if (isMatch)
            {
                Console.WriteLine("Successful match: " + test);
                foreach (Match match in Regex.Matches(test, segmentRegex))
                {
                    Console.WriteLine(match.Groups[1]);
                }
            }
        }
    }
}

Output:

Successful match: [A-Z,S,3][A-Za-z0-9,D,4]
A-Z,S,3
A-Za-z0-9,D,4
Successful match: [A-Z,S,3][klm,D,4][0-9,S,1]
A-Z,S,3
klm,D,4
0-9,S,1