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# std::thread::join

From cppreference.com
< cpp‎ | thread‎ | thread

void join(); |  | (since C++11)

Blocks the current thread until the thread identified by *this finishes its execution.

### [edit] Parameters

(none)

### [edit] Return value

(none)

### [edit] Preconditions

joinable is true

### [edit] Postconditions

joinable is false

### [edit] Exceptions

std::system_error if an error occurs.

### [edit] Error Conditions

- resource_deadlock_would_occur if this->get_id() == std::this_thread::get_id() (deadlock detected)
- no_such_process if the thread is not valid
- invalid_argument if joinable is false

### [edit] Example

Run this code

    #include <iostream>
    #include <thread>
    #include <chrono>

    void foo()
    {
        // simulate expensive operation
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }

    void bar()
    {
        // simulate expensive operation
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }

    int main()
    {
        std::cout << "starting first helper...\n";
        std::thread helper1(foo);

        std::cout << "starting second helper...\n";
        std::thread helper2(bar);

        std::cout << "waiting for helpers to finish..." << std::endl;
        helper1.join();
        helper2.join();

        std::cout << "done!\n";
    }

Output:

    starting first helper...
    starting second helper...
    waiting for helpers to finish...
    done!

### [edit] See also

detach | permits the thread to execute independently from the thread handle (public member function) [edit]
joinable | checks whether the thread is joinable, i.e. potentially running in parallel context (public member function) [edit]

### [edit] References

- C++11 standard (ISO/IEC 14882:2011):

  - 30.3.1.5 thread members [thread.thread.member]

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