Regex : how to optional capture a group

Question

I'm trying to make an substring optional. Here is the source :

Movie TOTO S09 E22 2022 Copyright

I want to optionally capture the substring : S09 E22

What I have tried so far :

/(Movie)(.*)(S\d\d\s*E\d\d)?/gmi

The problem is that it ends up by matching S09 E22 2022 Copyright instead of just S09 E22 :

Match 1 : 0-33  Movie TOTO S09 E22 2022 Copyright 
Group 1 : 0-5   Movie
Group 2:  5-33   TOTO S09 E22 2022 Copyright

Is there anyway to fix this issue ?

Regards

Answer 1

You get that match because the .* is greedy and will first match until the end of the string.

Then your (S\d\d\s*E\d\d)? is optional so this will stay matched and does not backtrack.

If you don't want partial matches for S09 or E22 and the 4 digits for the year are not mandatory and you have movies longer than 1 word, with pcre you could use:

\b(Movie)\b\h+((?:(?!\h+[SE]\d+\b).)*)(?:\h(S\d+\h+E\d+))?

• \b(Movie)\b Capture the word Movie
• ( Capture group
  • (?: Non capture group to repeat as a whole part
    • (?!\h+[SE]\d+\b). Match any character if either the S01 or E22 part is not directly to the right (where [SE] matches either a S or E char, and \h matches a horizontal whitespace char)
  • )* Close the non capture group and optionall repeat it
• ) Close capture group
• (?:\h(S\d+\h+E\d+)) Optionally capture the S01 E22 part (where \d+ matches 1 or more digits)

Regex demo

Another option with a capture group for the S01 E22 part, or else match the redt of the line

\b(Movie)\h+([^S\n]*(?:S(?!\d+\h+E\d+\b)[^S\n]*)*+)(S\d+\h+E\d+)?

Regex demo

Answer 2

With your shown samples and attempts please try following regex.

^Movie\s+\S+\s+(S\d{2}\s+E\d{2}(?=\s+\d{4}))

Here is the Online Demo for used regex.

Explanation: Adding detailed explanation for used regex above.

^Movie\s+\S+\s+  ##Matching string Movie from starting of value followed by spaces non-spaces and spaces.
(S\d{2}\s+E\d{2} ##Creating one and only capturing group where matching:
                 ##S followed by 2 digits followed by spaces followed by E and 2 digits.
  (?=\s+\d{4})   ##Making sure by positive lookahead that previous regex is followed by spaces and 4 digits.
)                ##Closing capturing group here.