C# Regex word match extractor

Question

ok i have a list of domains

for example

dogstoday . com
catstoday . com
petstoday . com
dogsnow . org
dogsabc . net
catlitter . info

i want a regex that will give me all domains that has the word i specify, for example dogs or cats

if i give dogs it should return

dogstoday.com
dogsnow.org
dogsabc.net

can any one tell me how to do this in c# ?

Answer 1

Does this need to be done with a regex? Why not just loop over all the domains and check if they contain the word you're looking for?

String.Contains()

Answer 2

string line;
System.Text.RegularExpressions.Regex r = new System.Text.RegularExpressions.Regex("dogs", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
using (System.IO.StreamReader reader = System.IO.File.OpenText("domains.txt"))
{
    while ((line = reader.ReadLine()) != null)
    {
        if (r.IsMatch(line))
        {
            Console.WriteLine(domain);
        }
    }
}

Answer 3

the regex is

/dogs/i

Answer 4

looks like you just need to use the StartsWith method.

Answer 5

If the domains always start with the word you provide as in your example, you can just use StartsWith otherwise you can simply use Contains. For something simple as this you don't need regular expressions.

Answer 6

Like others, I think grep would be better, but something like ...

Regex.Match( yourBigString, @".*dogs*.*[.com|.net|.org]" );

You should be careful of the domain as you might get some site like .au or .jp or whatever, but this will get anything with dogs in it followed by .com or .net or .org. You can replace "dogs" with anything you're looking for.