Match the first number/word/string in quotation marks in the Input - Regex Help

Question

Hi, I want to match the first number/word/string in quotation marks/list in the input with Regex. For example, it should match those:

"hello world" gdfigjfoj sogjds

-14.5 fdhdfdfi dfjgdlf

test14 hfghdf hjgfjd

(a (c b 7)) (3 4) "hi"

Any ideas to a regex or how can I start?

Thank you.

Answer 1

Any ideas to a regex or how can I start?

You can start with any tutorial on basic regex, such as this.

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[Edit] I missed that you wanted to count parentheses. That cannot be done in regex - nothing that involves counting (except for non-standard lookaheads) can.

Answer 2

If you want to match balanced parenthesis, regex is not the right tool for the job. Some regex implementations do facilitate recursive pattern matching (PHP and Perl, that I know of), but AFAIK, C# cannot do that (EDIT: see Steve's comment below: .NET can do this as well, after all).

You can match up to a certain depth using regex, but that very quickly explodes in your face. For example, this:

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

meaning

\(                        # match the character '('
(                         # start capture group 1
  [^()]                   #   match any character from the set {'0x00'..''', '*'..'ÿ'}
  |                       #   OR
  \(                      #   match the character '('
  [^()]*                  #   match any character from the set {'0x00'..''', '*'..'ÿ'} and repeat it zero or more times
  \)                      #   match the character ')'
)*                        # end capture group 1 and repeat it zero or more times
\)                        # match the character ')'

will match single nested parenthesis like (a (c b 7)) and (a (x) b (y) c (z) d), but will fail to match (a(b(c))).

Answer 3

For first three cases, you could to use:

^("[^"]*"|[+-]?\d*(?:\.\d+)?|\w+)

For last one, I'm not sure if it's possible with regex to match that last closing parenthesis.

EDIT: using that suggested balanced matching for last one:

^\([^()]*(((?<Open>\()[^()]*)+((?<Close-Open>\))[^()]*)+)*(?(Open)(?!))\)