std::thread::joinable

 

C++

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Thread support library

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std::thread

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

 

bool joinable() const;		(since C++11)

Checks if the thread object identifies an active thread of execution. Specifically, returns true if get_id() != std::thread::id(). So a default constructed thread is not joinable.

A thread that has finished executing code, but has not yet been joined is still considered an active thread of execution and is therefore joinable.

Parameters

(none)

Return value

true if the thread object identifies an active thread of execution, false otherwise

Exceptions

noexcept specification:  

noexcept

  

Example

Run this code

#include <iostream>
#include <thread>
#include <chrono>
 
void foo()
{
    std::this_thread::sleep_for(std::chrono::seconds(1));
}
 
int main()
{
    std::thread t;
    std::cout << "before starting, joinable: " << t.joinable() << '\n';
 
    t = std::thread(foo);
    std::cout << "after starting, joinable: " << t.joinable() << '\n';
 
    t.join();
}

Output:

before starting, joinable: 0
after starting, joinable: 1

See also

get_id	returns the id of the thread (public member function)
join	waits for a thread to finish its execution (public member function)
detach	permits the thread to execute independently from the thread handle (public member function)

References

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

• 30.3.1.5 thread members [thread.thread.member]