operator==,!=,<,<=,>,>=,<=>(std::thread::id)

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Concurrency support library

Threads thread (C++11) jthread (C++20) hardware_destructive_interference_sizehardware_constructive_interference_size (C++17)(C++17) this_thread namespace get_id (C++11) yield (C++11) sleep_for (C++11) sleep_until (C++11) Cooperative cancellation stop_token (C++20) inplace_stop_token (C++26) never_stop_token (C++26) stop_source (C++20) inplace_stop_source (C++26)   stop_callback (C++20) inplace_stop_callback (C++26) stop_callback_for_t (C++26) stoppable_token (C++26) unstoppable_token (C++26) stoppable-source (C++26) stoppable-callback-for (C++26)   Mutual exclusion mutex (C++11) recursive_mutex (C++11) shared_mutex (C++17) timed_mutex (C++11) recursive_timed_mutex (C++11) shared_timed_mutex (C++14) Generic lock management lock (C++11) lock_guard (C++11) scoped_lock (C++17) unique_lock (C++11) shared_lock (C++14) once_flag (C++11) call_once (C++11) try_lock (C++11) defer_locktry_to_lockadopt_lockdefer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11)(C++11)(C++11)(C++11) Condition variables condition_variable (C++11) condition_variable_any (C++11) notify_all_at_thread_exit (C++11) cv_status (C++11) Semaphores counting_semaphorebinary_semaphore (C++20)(C++20) Latches and Barriers latch (C++20) barrier (C++20) Futures promise (C++11) future (C++11) shared_future (C++11) packaged_task (C++11) async (C++11) launch (C++11) future_status (C++11) future_error (C++11) future_category (C++11) future_errc (C++11) Safe Reclamation rcu_obj_base (C++26) rcu_domain (C++26) rcu_default_domain (C++26) rcu_synchronize (C++26) rcu_barrier (C++26) rcu_retire (C++26) Hazard Pointers hazard_pointer_obj_base (C++26) hazard_pointer (C++26) make_hazard_pointer (C++26)

Atomic types atomic (C++11) atomic_ref (C++20) atomic_flag (C++11) Initialization of atomic types atomic_init (C++11)(deprecated in C++20) ATOMIC_VAR_INIT (C++11)(deprecated in C++20) ATOMIC_FLAG_INIT (C++11) Memory ordering memory_order (C++11) kill_dependency (C++11) atomic_thread_fence (C++11) atomic_signal_fence (C++11) Free functions for atomic operations atomic_storeatomic_store_explicit (C++11)(C++11) atomic_loadatomic_load_explicit (C++11)(C++11) atomic_exchangeatomic_exchange_explicit (C++11)(C++11) atomic_compare_exchange_weakatomic_compare_exchange_weak_explicitatomic_compare_exchange_strongatomic_compare_exchange_strong_explicit (C++11)(C++11)(C++11)(C++11) atomic_fetch_addatomic_fetch_add_explicit (C++11)(C++11) atomic_fetch_subatomic_fetch_sub_explicit (C++11)(C++11) atomic_fetch_andatomic_fetch_and_explicit (C++11)(C++11) atomic_fetch_oratomic_fetch_or_explicit (C++11)(C++11) atomic_fetch_xoratomic_fetch_xor_explicit (C++11)(C++11) atomic_fetch_maxatomic_fetch_max_explicit (C++26)(C++26) atomic_fetch_minatomic_fetch_min_explicit (C++26)(C++26) atomic_is_lock_free (C++11) atomic_waitatomic_wait_explicit (C++20)(C++20) atomic_notify_one (C++20) atomic_notify_all (C++20) Free functions for atomic flags atomic_flag_test_and_setatomic_flag_test_and_set_explicit (C++11)(C++11) atomic_flag_clearatomic_flag_clear_explicit (C++11)(C++11) atomic_flag_testatomic_flag_test_explicit (C++20)(C++20) atomic_flag_waitatomic_flag_wait_explicit (C++20)(C++20) atomic_flag_notify_one (C++20) atomic_flag_notify_all (C++20)

 

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

swap(std::thread) (C++11)

 

std::thread::id

Member functions

id::id

Non-member functions

operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

operator<<

Helper classes

hash<std::thread::id>

formatter<std::thread::id> (C++23)

 

Defined in header <thread>
bool operator==( std::thread::id lhs, std::thread::id rhs ) noexcept;	(1)	(since C++11)
bool operator!=( std::thread::id lhs, std::thread::id rhs ) noexcept;	(2)	(since C++11) (until C++20)
bool operator< ( std::thread::id lhs, std::thread::id rhs ) noexcept;	(3)	(since C++11) (until C++20)
bool operator<=( std::thread::id lhs, std::thread::id rhs ) noexcept;	(4)	(since C++11) (until C++20)
bool operator> ( std::thread::id lhs, std::thread::id rhs ) noexcept;	(5)	(since C++11) (until C++20)
bool operator>=( std::thread::id lhs, std::thread::id rhs ) noexcept;	(6)	(since C++11) (until C++20)
std::strong_ordering operator<=>( std::thread::id lhs,                                   std::thread::id rhs ) noexcept;	(7)	(since C++20)

Compares two thread identifiers.

1,2) Checks whether lhs and rhs represent either the same thread, or no thread.

3-7) Compares lhs and rhs in an unspecified total ordering.

The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.

(since C++20)

Parameters

lhs, rhs

-

thread identifiers to compare

Return value

1-6) true if the corresponding relation holds, false otherwise.

7) std::strong_ordering::less if lhs is less than rhs in the total ordering; otherwise std::strong_ordering::greater if rhs is less than lhs in the total ordering; otherwise std::strong_ordering::equal.

Complexity

Constant.

Example

Run this code

#include <cassert>
#include <chrono>
#include <iostream>
#include <thread>
 
 
int main()
{
    auto work = [] { std::this_thread::sleep_for(std::chrono::seconds(1)); };
    std::thread t1(work);
    std::thread t2(work);
 
    assert(t1.get_id() == t1.get_id() and
           t2.get_id() == t2.get_id() and
           t1.get_id() != t2.get_id());
 
    if (const auto cmp = t1.get_id() <=> t2.get_id(); cmp < 0)
        std::cout << "id1 < id2\n";
    else
        std::cout << "id1 > id2\n";
 
    std::cout << "id1: " << t1.get_id() << "\n"
                 "id2: " << t2.get_id() << '\n';
 
    t1.join();
    t2.join();
}

Possible output:

id1 > id2
id1: 139741717640896
id2: 139741709248192

See also

C documentation for thrd_equal