# <regex>

**[<regex>](https://en.cppreference.com/w/cpp/header/regex)** provides regular expression matching via `std::regex`, `std::regex_match`, `std::regex_search`, and `std::regex_replace`. The syntax defaults to ECMAScript (JavaScript-like) regex.

C++ regex is slower than dedicated libraries like `oniguruma` or `PCRE2`, but is portable and does not require external dependencies.

## Example

This example searches for a regex pattern in a string and performs a regex-based replacement to modify text.

```cpp
// compile: g++ -std=c++11 -o regexexample regexexample.cpp
// run: ./regexexample
// description: regex matching and replacement

#include <regex>
#include <iostream>
#include <string>

int main() {
    std::string text = "hello world";
    std::regex pattern("l+o");
    
    if (std::regex_search(text, pattern)) {
        std::cout << "found match\n";
    }
    
    std::string result = std::regex_replace(text, pattern, "X");
    std::cout << "after replace: " << result << "\n";
    
    return 0;
}
```