Difference between regex_match and regex_search?

Question

I was experimenting with regular expression in trying to make an answer to this question, and found that while regex_match finds a match, regex_search

Answer 1

Your regex works fine (both match, which is correct) in VS 2012rc.

In g++ 4.7.1 (-std=gnu++11), if using:

• ".*FILE_(.+)_EVENT\\.DAT.*", regex_match matches, but regex_search doesn't.
• ".*?FILE_(.+?)_EVENT\\.DAT.*", neither regex_match nor regex_search matches (O_o).

All variants should match but some don't (for reasons that have been pointed out already by betabandido). In g++ 4.6.3 (-std=gnu++0x), the behavior is identical to g++ 4.7.1.

Boost (1.50) matches everything correctly w/both pattern varieties.

Summary:

                        regex_match      regex_search
 -----------------------------------------------------
 g++ 4.6.3 linux            OK/-               -
 g++ 4.7.1 linux            OK/-               -
 vs 2010                     OK                OK
 vs 2012rc                   OK                OK
 boost 1.50 win              OK                OK
 boost 1.50 linux            OK                OK
 -----------------------------------------------------

Regarding your pattern, if you mean a dot character '.', then you should write so ("\\."). You can also reduce backtracking by using non-greedy modifiers (?):

".*?FILE_(.+?)_EVENT\\.DAT.*"