Regex match for 3 numbers

Question

Hello,

 

I am trying to find a 3 digit numeric string in a sentence.  The regex expression I am using is "\d{3}".  This works for strings like "100", but it also matches strings like "9999".  I would just like a match for "999" but not "9999".

 

What regex should I use in this case?

 

Thanks

Tom

 

Answer 1

the answer depends on the text u r processing and how the processing is implelentedd. pls post details.

 

for one: do u process on one-string-at-a-time basis OR u r processing the whole chunk of multiline text? It depends..

 

that's why people on forums are always advised not to save on keyboard clicks and privide more details...

Answer 2

How about:

 

Code Snippet

"\D?(\d{3})\D?"

 

Answer 3

\D/\d{3}\D?

 

 still will match on bolded part of this input:

 

12389

 

unless we know details of text processing [processing a string or the whole text/sentence? ], we can't really know how to match \d{3} in the target text.

Answer 4

Mister T554781 wrote:

The regex expression I am using is "\d{3}". This works for strings like "100", but it also matches strings like "9999". I would just like a match for "999" but not "9999".

I agree with Sergei...more info is needed but in answering the basic question about eliminating a match so it only matches three numerics, use \b which signifies word boudaies such as

\b\d{1,3}\b

which will look for words of digits, 1-3 in length, such as

1
12
123

but not

1234

Answer 5

Thanks to everyone for their reply.

 

I am taking a sentence and splitting it into a string array.   Then looping thru the array to find the match.

 

Dim myRegex As New Regex("\d{3}", RegexOptions.IgnoreCase)

Dim words() as String = "This is a test 100 9999 22".Split(" ")

 

Dim word as string = ""

 

For Each word in words

   If myRegex.IsMatch(word) Then

      Return word

   End If

Next

 

Thanks for any ideas,

Tom

 

Answer 6

Why not let regex do the parsing? The following regex will extract the words and number into named capture groups of Number, TooBig and Word. All you have to do is check the current match for a Number and it is guareenteed to be 1-3 in size.  Note match index 0 is the whole match. You will want to index via the named capture group not the index number.

Input Text

This is a test 100 9999 22

Regular Expression

(?(\b\d+\b)            # If it is a number
  (?(\b\d{1,3}\b)      # Then If it is 1-3 digits
    (?<Number>\b\d+\b) # Capture to the Number named group
   |
    (?<TooBig>[^\s]*)  # Too big of a number. 
   )
 |                     # Or from the first if
  (?<Word>[^\s.!?]*)   # It is a word
)
(?:\s?|$|[.?!])        # Capture but don't match the nonwords.

Group Captures

Groups: (0) (Number) (TooBig) (Word)

---

Match (1):
              0 : This 
         Number : 
         TooBig : 
           Word : This

Match (2):
              0 : is 
         Number : 
         TooBig : 
           Word : is

Match (3):
              0 : a 
         Number : 
         TooBig : 
           Word : a

Match (4):
              0 : test 
         Number : 
         TooBig : 
           Word : test

Match (5):
              0 : 100 
         Number : 100
         TooBig : 
           Word : 

Match (6):
              0 : 9999 
         Number : 
         TooBig : 9999
           Word : 

Match (7):
              0 : 22
         Number : 22
         TooBig : 
           Word : 

Match (8):
              0 : 
         Number : 
         TooBig : 
           Word : 

Regex Options

                                                                                            

Compile	ECMA	Single Line	Multi Line	Ignore White Space	Explicit Capture	Ignore Case	Right To Left	Culture Invariant
				✓

Regex Info Generated by the Regex Responder V1.0

Answer 7

OmegaMan,

 

Thanks for your answer!

 

I will checkout your Regex Responder too.  It looks like a real time saver.

 

Thanks

Tom

 

Answer 8

Mister T554781 wrote:

OmegaMan, Thanks for your answer! I will checkout your Regex Responder too. It looks like a real time saver. Thanks Tom

The responder is only for responding to HTML forum posts and not for general regex uses. I recommend you use Ultrapico's (Expresso 3.0) to work out the kinks with regex patterns before using them in code.

Answer 9

Hello OmegaMan,

 

Can you please elaborate a bit on your solution? Is (?) some kind of a conditional pattern? I have not seen this before. I appreciate your contribution to this forum.

Answer 10

Hi J2,

I have done just that on my blog entitled, Regular Expressions and the If Conditional which discusses this solution. Let me know if it helps...

Answer 11

Very helpful. Thanks for the link!