スレッド関数pthread_equal

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

int main(){
    pthread_t thread_id;

    thread_id=pthread_self(); //          ID
    printf("Thread ID: %lu.
",thread_id);

    if (pthread_equal(thread_id,pthread_self()))
     {
        printf("Equal!
");
     } else {
        printf("Not equal!
");
    }
    return 0;
}