threads.h
- C course
- Expert
- Lesson 29/47
- 5 min
Learn standard threads with threads.h.
threads.h threads
The threads.h header is the standard thread library introduced in C11. thrd_create(&t, func, arg) starts a new thread; thrd_join(t, &result) waits for it.
This header also provides the mtx_t mutex type. mtx_lock(&m) locks it, mtx_unlock(&m) unlocks it. It is similar to POSIX pthread but is part of standard C, so it is portable. The thread function must have the signature int (*)(void *); its return value is retrieved via thrd_join.
The thread function
The thread function must have the signature int thread_func(void *arg). The arg parameter is passed via the third argument of thrd_create; its type is void *.
The function returns an int, retrieved via the second parameter of thrd_join. Returning thrd_success is conventional for success. If arg is unused, (void)arg; suppresses the unused-parameter warning. You can call printf inside the thread function; output ordering is guaranteed by thrd_join.
Practice Start a thread and join
Add #include <threads.h>. Write int thread_func(void *arg); suppress the warning with (void)arg;, print printf("İş parçacığı\n"), return 0;. In int main(void) declare thrd_t t;, call thrd_create(&t, thread_func, NULL) and thrd_join(t, NULL), then print printf("Bitti\n").
Starter code
#include <stdio.h>
#include <threads.h>
// parçacık fonksiyonu yaz
// başlat ve bekle
// main'de "Bitti" yazdırSample solution
#include <stdio.h>
#include <threads.h>
int thread_func(void *arg) {
(void)arg;
printf("İş parçacığı\n");
return 0;
}
int main(void) {
thrd_t t;
thrd_create(&t, thread_func, NULL);
thrd_join(t, NULL);
printf("Bitti\n");
return 0;
}Expected output
İş parçacığı Bitti
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match the threads.h function
| Term | Meaning |
|---|---|
thrd_create |
Start thread |
thrd_join |
Wait thread |
mtx_lock |
Lock |
mtx_unlock |
Unlock |
2 Which function starts a new thread?
- thrd_create Correct answer
- pthread_create
- thread_create
- _beginthread
Explanation: thrd_create is the thread-start function in threads.h.
3 Complete the thrd_join call
thrd_create(&t, thread_func, NULL);
____(t, NULL);thrd_create(&t, thread_func, NULL);
thrd_join(t, NULL);Explanation: thrd_join(t, NULL) waits for the thread to finish.