How to match a pattern multiple times within a string and replace them

I want to find all instances of Foo inside #include preprocessor using regex. so far, I can only match one instance using this pattern #include "(.*?)Foo(.*?)". and to replace Foo with Bar i use this substitution #include "$1Bar$2"

When I replace Foo with Bar, the following example

#include "abcFoo1/Foo123/aFoo"

becomes

#include "abcBar1/Foo123/aFoo"

I'm stuck trying to figure out how to make it match all instances of Foo within the #include statement and get the following result after replacement.

#include "abcBar1/Bar123/aBar"

P.S. I'm trying to do this for many strings using a text editor such as Notepad++ or IDE like Visual Studio.

You can use this regex in e.g. Notepad++ (or anything that uses PCRE) if you want to do it in one go:

(?:#include ".*?|(?<!^)\G.*?)\KFoo

Breakdown:

• (?:#include ".*?|(?<!^)\G.*?) - non-captured group with 2 alternatives:

1. #include ".*? - the start of your string followed by non-greedily matched anything
2. (?<!^)\G.*? - \G is the position at the end of previous match, followed by non-greedy anything as above. Using \G is required here, since otherwise the regex engine won't match the same parts twice. (?<!^) negative lookbehind of the start of the line is there to not match cases in which there would be something with Foo above #includes (as \G starts at the start of the string), which shouldn't happen and is likely optional, but included it just in case, for a full solution.

• \K - don't include anything before this in the match, so that only the next part gets matched
• Foo - the part that you want to replace

We're matching only Foos, so the replacement should be just Bar.

Also, in Notepad++, . matches newline option needs to be turned off.

Demo with detailed explantation

On Notepad++ or Sublime text, you click Ctrl+H, you get the find+replace bar,
you write Foo in the find field, then Bar in the Replace, and it should be good.

no need for a complex regex pattern I believe.

Instead of looking for a string with Foo to replace it with Bar, look for Foo which has #include behind

(?=Foo)(?<=#include .*)Foo

or

Foo(?<=#include .*Foo)

If the filename should be between double quotes, and you don't want to match crossing a double quote by itself:

(?:#include\h+"(?=[^"\r\n]*")|\G(?!^))[^"\r\n]*?\KFoo

Explanation

• (?: Non capture group for the alternatives
  • #include\h+" Match #include followed by 1+ horizontal whitespace chars
  • (?=[^"\r\n]*") Positive lookahead, assert a " to the right on the same line
  • | Or
  • \G(?!^) Assert the current position at the end of the previous match, not at the start of the string
• ) Close the non capture goru
• [^"\r\n]*? Match optional chars other than " or a newline
• \KFoo Forget what is matches so far and match Foo

Regex demo

If the string should not contain spaces, you can use \s in the negated character class:

(?:#include\h+"(?=[^"\s]*")|\G(?!^))[^"\s]*?\KFoo

Regex demo