# <mutex>

**[<mutex>](https://en.cppreference.com/w/cpp/header/mutex)** provides `std::mutex` for mutual exclusion, and `std::lock_guard<Mutex>` / `std::unique_lock<Mutex>` for RAII-based locking. Always lock via a lock guard to ensure the lock is released even if an exception is thrown.

Use `std::lock_guard` for simple cases; use `std::unique_lock` when you need to unlock before scope end or transfer lock ownership.

## Example

This example protects a shared counter with a mutex, having two threads each increment it 100 times safely.

```cpp
// compile: g++ -std=c++11 -pthread -o mutexexample mutexexample.cpp
// run: ./mutexexample
// description: protect shared data with mutex

#include <mutex>
#include <iostream>
#include <thread>

int counter = 0;
std::mutex mtx;

void increment() {
    for (int i = 0; i < 100; ++i) {
        std::lock_guard<std::mutex> lock(mtx);
        counter++;
    }
}

int main() {
    std::thread t1(increment);
    std::thread t2(increment);
    
    t1.join();
    t2.join();
    
    std::cout << "final counter: " << counter << "\n";
    
    return 0;
}
```