std::mutex(3)

NAME
std::mutex - std::mutex

Synopsis
   Defined in header <mutex>
   class mutex; (since C++11)
   The mutex class is a synchronization primitive that can be used to protect shared
   data from being simultaneously accessed by multiple threads.
   mutex offers exclusive, non-recursive ownership semantics:
     * A calling thread owns a mutex from the time that it successfully calls either
       lock or try_lock until it calls unlock.
     * When a thread owns a mutex, all other threads will block (for calls to lock) or
       receive a false return value (for try_lock) if they attempt to claim ownership
       of the mutex.
     * A calling thread must not own the mutex prior to calling lock or try_lock.
   The behavior of a program is undefined if a mutex is destroyed while still owned by
   any threads, or a thread terminates while owning a mutex. The mutex class satisfies
   all requirements of Mutex and StandardLayoutType.
   std::mutex is neither copyable nor movable.

Member types
   Member type Definition
   native_handle_type(not always present) implementation-defined

Member functions
   constructor constructs the mutex
                 (public member function)
   destructor destroys the mutex
                 (public member function)
   operator= not copy-assignable
   [deleted] (public member function)

Locking
   lock locks the mutex, blocks if the mutex is not available
                 (public member function)
   try_lock tries to lock the mutex, returns if the mutex is not available
                 (public member function)
   unlock unlocks the mutex
                 (public member function)

Native handle
   native_handle returns the underlying implementation-defined native handle object
                 (public member function)

Notes
   std::mutex is usually not accessed directly: std::unique_lock, std::lock_guard,
   or std::scoped_lock
   (since C++17) manage locking in a more exception-safe manner.

Example
   This example shows how a mutex can be used to protect an std::map shared between two
   threads. // Run this code
 #include <iostream>
 #include <map>
 #include <string>
 #include <chrono>
 #include <thread>
 #include <mutex>
 std::map<std::string, std::string> g_pages;
 std::mutex g_pages_mutex;
 void save_page(const std::string &url)
 {
     // simulate a long page fetch
     std::this_thread::sleep_for(std::chrono::seconds(2));
     std::string result = "fake content";
     std::lock_guard<std::mutex> guard(g_pages_mutex);
     g_pages[url] = result;
 }
 int main()
 {
     std::thread t1(save_page, "http://foo");
     std::thread t2(save_page, "http://bar");
     t1.join();
     t2.join();
     // safe to access g_pages without lock now, as the threads are joined
     for (const auto &pair : g_pages) {
         std::cout << pair.first << " => " << pair.second << '\n';
     }
 }

Output:
 http://bar => fake content
 http://foo => fake content

See also
   recursive_mutex provides mutual exclusion facility which can be locked
   (C++11) recursively by the same thread
                      (class)
   lock_guard implements a strictly scope-based mutex ownership wrapper
   (C++11) (class template)
   unique_lock implements movable mutex ownership wrapper
   (C++11) (class template)
   scoped_lock deadlock-avoiding RAII wrapper for multiple mutexes
   (C++17) (class template)
   condition_variable provides a condition variable associated with a std::unique_lock
   (C++11) (class)