C# Regular Expression excluding a string

Question

I got a collection of string and all i want for regex is to collect all started with http..

href="http://www.test.com/cat/1-one_piece_episodes/"href="http://www.test.com/cat/2-movies_english_subbed/"href="http://www.test.com/cat/3-english_dubbed/"href="http://www.exclude.com"

this is my regular expression pattern..

href="(.*?)[^#]"

and return this

href="http://www.test.com/cat/1-one_piece_episodes/"
href="http://www.test.com/cat/2-movies_english_subbed/"
href="http://www.xxxx.com/cat/3-english_dubbed/"
href="http://www.exclude.com"

what is the pattern for excluding the last match.. or excluding matches that has the exclude domain inside like href="http://www.exclude.com"

EDIT: for multiple exclusion

href="((?:(?!"|\bexclude\b|\bxxxx\b).)*)[^#]"

Would you want the url http://www.test.com/fish/exclude included? what about http://www.exclude.co.uk or http://www.exclude.test.com — Bob Vale
– Bob Vale, Commented Aug 5, 2011 at 12:24

Tim Pietzcker · Accepted Answer · 2011-08-05 14:26:42Z

17

@ridgerunner and me would change the regex to:

href="((?:(?!\bexclude\b)[^"])*)[^#]"

It matches all href attributes as long as they don't end in # and don't contain the word exclude.

Explanation:

href="     # Match href="
(          # Capture...
 (?:       # the following group:
  (?!      # Look ahead to check that the next part of the string isn't...
   \b      # the entire word
   exclude # exclude
   \b      # (\b are word boundary anchors)
  )        # End of lookahead
  [^"]     # If successful, match any character except for a quote
 )*        # Repeat as often as possible
)          # End of capturing group 1
[^#]"      # Match a non-# character and the closing quote.

To allow multiple "forbidden words":

href="((?:(?!\b(?:exclude|this|too)\b)[^"])*)[^#]"

edited Aug 5, 2011 at 14:26

answered Aug 5, 2011 at 12:15

Tim Pietzcker

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5 Comments

Vincent Dagpin Over a year ago

parsing "href="((?:(?!"|\bexclude\b).)*[^#]"" - Not enough )'s its ok now.. i just read the explanation.. href="((?:(?!"|\bexclude\b).)*)[^#]"

Vincent Dagpin Over a year ago

additional question sir.. how about if i exclude additional string xxxx ?

Tim Pietzcker Over a year ago

@vrynxzent: Sorry, I had dropped a closing parenthesis. But you have found the correct solution, obviously :)

Mrchief Over a year ago

+1 for this awesome explanation! I know regex editors that do this but somehow, looking at their output I was always perplexed. Yours is so much succinct!

Tim Pietzcker Over a year ago

@ridgerunner: Thanks! I had planned to do this but forgot it completely when writing the regex...

Mrchief · Accepted Answer · 2011-08-05 12:19:49Z

2

Your input doesn't look like a valid string (unless you escape the quotes in them) but you can do it without regex too:

string input = "href=\"http://www.test.com/cat/1-one_piece_episodes/\"href=\"http://www.test.com/cat/2-movies_english_subbed/\"href=\"http://www.test.com/cat/3-english_dubbed/\"href=\"http://www.exclude.com\"";

List<string> matches = new List<string>();

foreach(var match in input.split(new string[]{"href"})) {
   if(!match.Contains("exclude.com"))
      matches.Add("href" + match);
}

answered Aug 5, 2011 at 12:19

Mrchief

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Comments

Bob Vale · Accepted Answer · 2011-08-05 12:18:11Z

0

Will this do the job?

href="(?!http://[^/"]+exclude.com)(.*?)[^#]"

answered Aug 5, 2011 at 12:18

Bob Vale

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