Question

I want to create a regular expression to match a word that begins with a period. The word(s) can exist N times in a string. I want to ensure that the word comes up whether it’s at the beginning of a line, the end of a line or somewhere in the middle. The latter part is what I’m having difficulty with.

Here is where I am at so far.

const string pattern = @"(^|(.* ))(?<slickText>\.[a-zA-Z0-9]*)( .*|$)";

public static MatchCollection Find(string input)
{
    Regex regex = new Regex(pattern,RegexOptions.IgnoreCase | RegexOptions.Multiline);
    MatchCollection collection = regex.Matches(input);
    return collection;
}

My test pattern finds .lee and .good. My test pattern fails to find .bruce:

static void Main()
{
    MatchCollection results = ClassName.Find("a short stump .bruce\r\nand .lee a small tree\r\n.good roots");

    foreach (Match item in results)
    {
        GroupCollection groups = item.Groups;
        Console.WriteLine("{0} ", groups["slickText"].Value);

    }
    System.Diagnostics.Debug.Assert(results.Count > 0);
}

Answer 1

Maybe you’re just looking for \.\w+?

Test:

var s = "a short stump .bruce\r\nand .lee a small tree\r\n.good roots";
Regex.Matches(s, @"\.\w+").Dump();

Result:

Note:

If you don’t want to find foo in some.foo (because there’s no whitespace between some and .foo), you can use (?<=\W|^)\.\w+ instead.