Regex to capture everything after optional token

user_13902318 0
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I have fields which contain data in the following possible formats (each line is a different possibility):

AAA - Something Here  
AAA - Something Here - D  
Something Here

Note that the first group of letters (AAA) can be of varying lengths.

What I am trying to capture is the "Something Here" or "Something Here - D" (if it exists) using PCRE, but I can't get the Regex to work properly for all three cases. I have tried:

- (.*) which works fine for cases 1 and 2 but obviously not 3;

(?<= - )(.*) which also works fine for cases 1 and 2;

(?! - )(.+)| - (.+) works for cases 2 and 3 but not 1.

I feel like I'm on the verge of it but I can't seem to crack it.

Thanks in advance for your help.

Edit: I realized that I was unclear in my requirements. If there is a trailing " - D" (the letter in the data is arbitrary but should only be a single character), that needs to be captured as well.

pcre regex
3 Answers

You may use

^(?:.*? - )?\K.*?(?= - | *$)
^(?:.*?\h-\h)?\K.*?(?=\h-\h|\h*$)

See the regex demo

Details

  • ^ - start of string -(?:.*? - )? - an optional non-capturing group matching any 0+ chars other than line break chars as few as possible up to the first space-space
  • \K - match reset operator
  • .*? - any 0+ chars other than line break chars as few as possible
  • (?= - | *$) - space-space or 0+ spaces till the end of string should follow immediately on the right.

Note that \h matches any horizontal whitespace chars.

user_38329700

About the patterns that you tried:

  • - (.*)This pattern will match the first occurrence of - followed by matching the rest of the line. It will match too much for the second example as the .* will also match the second occurrence of -
  • (?<= - )(.*)This pattern will match the same as the first example without the - as it asserts that is should occur directly to the left
  • (?! - )(.+)| - (.+) This pattern uses a negative lookahead which asserts what is directly to the right is not (?! - ). As none of the example start with - , the whole line will be matched directly after the negative lookahead due to .+ and the second part after the alternation | will not be evaluated

If the first group of letters can be of varying length, you could make the match either specific matching 1 or more uppercase characters [A-Z]+ or 1+ word characters \w+.

To get a more broad match, you could match 1 or more non whitespace characters using \S+

^(?:\S+\h-\h)?\K\S+(?:\h(?!-\h)\S+)*

Explanation

  • ^ Start of string
  • (?:\S+\h-\h)? Optionally match the first group of non whitespace chars followed by - between horizontal whitespace chars
  • \K Clear the match buffer (Forget what is currently matched)
  • \S+ Match 1+ non whitespace characters
  • (?: Non capture group
    • \h(?!-\h) Match a horizontal whitespace char and assert what is directly to the right is not - followed by another horizontal whitespace char
    • \S+ Match 1+ non whitespace chars
  • )* Close non capture group and repeat 1+ times to match more "words" separated by spaces

Regex demo

Edit

To match an optional hyphen and trailing single character, you could add an optional non capturing group (?:-\h\S\h*)?$ and assert the end of the string if the pattern should match the whole string:

^(?:\S+\h-\h)?\K\S+(?:\h(?!-\h)\S+)*\h*(?:-\h\S\h*)?$

Regex demo

user_54249880 
^(?:[A-Z]+ - \K)?.*\S

demo

Since "Something Here" can be anything, there's no reason to specially describe the eventual last letter in the pattern. You don't need something more complicated.

With this pattern I assume that you are not interested by the trailing spaces, that's why I ended it with \S. If you want to keep them, remove the \S and change the previous quantifier to +.

user_22550890
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