Regular Expressions 101

Pro

#ifdefthe literal text #ifdef (case sensitive)

\s+a Unicode whitespace character, repeated at least once

TYPEAthe literal text TYPEA (case sensitive)

\s*a Unicode whitespace character, repeated any number of times

Group 1(.*?)

.*?any Unicode character, repeated any number of times

Positive Lookahead(?=\s*#(?:else|endif))

\s*a Unicode whitespace character, repeated any number of times

#the literal # (35₁₀ / 43₈ / 23₁₆)

Non-Capturing Group(?:else|endif)

1st Alternativeelse

elsethe literal text else (case sensitive)

2nd Alternativeendif

endifthe literal text endif (case sensitive)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

s modifier: single line. Allows a dot to match line terminators

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

#ifdef\s+TYPEA\s*(.*?)(?=\s*#(?:else|endif))

New

#ifdef TYPEZERO
  int someint = 42;
#endif
void abc ( int value) {
  return 5 ** 2.5
}

abc
#ifdef TYPEA
#include "some_header.h"
           #include "some_other_header23.h"
           #else        
double in_fact_int = 5;
         #endif    

a = 5
#ifdef TYPEB
  abc = 23.5;
#endif

abc
#ifdef TYPEA
#include "some_header.h"
           #include "some_other_header23.h"
           #else        
double in_fact_int = 5;
         #endif    

a = 5
#ifdef TYPEB
  abc = 23.5;
#endif