CODEWITHSUNDEEP
c#regex
MaxOvrdrv
MaxOvrdrv

Reputation: 1916

Regex in square brackets not preceeded or followed by

I am trying to create a Regex pattern in C# to find in a string, any [anything] that is not preceeded or followed by a "."... here is the pattern i have so far, which brings me to the actual problem: it only works on text that is NOT on the very first line??

Pattern:

([^\.]\[[^\[]*][^\.])

Consider the following "text" value:

[F] (never matches even if it should)

[F].[1234] (not a match, correct)

[P] (is a match)

If someone could help me with this, i would really appreciate it because i cannot, for the life of me, figure out why the very first line is not considered.

Thanks!

Upvotes: 1

Views: 70

Answers (2)

MyDogTom
MyDogTom

Reputation: 4606

you can also use this pattern:

((^|[^\.])\[[^\[]*][^\.])

difference against yours is that [ could be just the first symbol in the line.

also i suggest you to use a site like http://regex101.com/ to better understand how regex works.

Upvotes: 0

dee-see
dee-see

Reputation: 24078

Your regex as you wrote it validates that the first [ must have a character that is not . in front of it. The first [ is not preceded by any character so it fails.

With negative assertions you can say "match if there is no .".

((?<!\.)\[[^\[]*](?!\.))


NODE                     EXPLANATION
--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    (?<!                     look behind to see if there is not:
--------------------------------------------------------------------------------
      \.                       '.'
--------------------------------------------------------------------------------
    )                        end of look-behind
--------------------------------------------------------------------------------
    \[                       '['
--------------------------------------------------------------------------------
    [^\[]*                   any character except: '\[' (0 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    ]                        ']'
--------------------------------------------------------------------------------
    (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
      \.                       '.'
--------------------------------------------------------------------------------
    )                        end of look-ahead
--------------------------------------------------------------------------------
  )                        end of \1

Upvotes: 4

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