Question

I have a test list that I am trying to capture data from using a regex.

Here is a sample of the text format:

(1) this is a sample string /(2) something strange /(3) another bit of text /(4) the last one/ something!/

I have a Regex that currently captures this correctly, but I am having some difficulty with making it work under outlier conditions.

Here is my regex

/\(?\d\d?\)([^\)]+)(\/|\z)/

Unfortunately some of the data contains parentheses like this:

(1) this is a sample string (1998-1999) /(2) something strange (blah) /(3) another bit of text /(4) the last one/ something!/

The substrings ‘(1998-1999)’ and ‘(blah)’ make it fail!

Anyone care to have a crack at this one?
Thank you 😀

Answer 1

I would try this:

\((\d+)\)\s+(.*?)(?=/(?:\(\d+\)|\z))

This rather scary looking regex does the following:

• It looks for one or more digits wrapped in parentheses and captures them;
• There must be at least one white space character after the digits in parentheses. This white space is ignored (not captured);
• A non-greedy wildcard expression is used. This is (imho) the preferable way to using negative character groups (eg [^/]+) for this kind of problem;
• The positive lookahead ((?=...)) says the expression must be followed by a backslash and then one of:
  • one or more digits wrapped in parentheses; or
  • the string terminator.

To give you an example in PHP (you don’t specify your language):

$s = '(1) this is a sample string (1998-1999) /(2) something strange (blah) /(3) another bit of text /(4) the last one/ something!/';
preg_match_all('!\((\d+)\)\s+(.*?)(?=/(?:\(\d+\)|\z))!', $s, $matches);
print_r($matches);

Output:

Array
(
    [0] => Array
        (
            [0] => (1) this is a sample string (1998-1999) 
            [1] => (2) something strange (blah) 
            [2] => (3) another bit of text 
            [3] => (4) the last one/ something!
        )

    [1] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
        )

    [2] => Array
        (
            [0] => this is a sample string (1998-1999) 
            [1] => something strange (blah) 
            [2] => another bit of text 
            [3] => the last one/ something!
        )

)

Some notes:

• You don’t specify what you want to capture. I’ve assumed the list item number and the text. This could be wrong in which case just drop those capturing parentheses. Either way you can get the whole match;
• I’ve dropped the trailing slash from the match. This may not be your intent. Again just change the capturing to suit;
• I’ve allowed any number of digits for the item number. Your version allowed only two. If you prefer it that way replace \d+ with \d\d?.