std::thread::join

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

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

The completion of the thread identified by *this synchronizes with the corresponding successful return from join().

Parameters

(none)

Return value

(none)

Postconditions

joinable is false

Exceptions

std::system_error if an error occurs.

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

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!

References

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

30.3.1.5 thread members [thread.thread.member]

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Member classes
thread::id
Member functions
thread::thread
thread::~thread
thread::operator=
Observers
thread::joinable
thread::get_id
thread::native_handle
thread::hardware_concurrency
Operations
thread::join
thread::detach
thread::swap
Non-member functions
std::swap

detach	permits the thread to execute independently from the thread handle (public member function)
joinable	checks whether the thread is joinable, i.e. potentially running in parallel context (public member function)
C documentation for thrd_join