The unknown semaphore is synchronized between multiple threads

The common usage of the nameless semaphore is that the variable to be protected is placed in the critical region formed between the sem_wait and the sem_post, so that the variable is//protected, for example:
#include <pthread.h>
#include <semaphore.h>
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
int number;//protected global variable
sem_t sem_id;
void* thread_one_fun (void *arg)
{
sem_wait (&sem_id);
printf ("Thread_one has the semaphore\n");
number++;
printf ("number =%d\n", number);
Sem_post (&sem_id);
}

void* thread_two_fun (void *arg)
{
sem_wait (&sem_id);
printf ("Thread_two has the semaphore \ n");
number--;
printf ("number =%d\n", number);
Sem_post (&sem_id);
}

int main (int argc,char *argv[])
{
Number = 1;
pthread_t id1, Id2;
sem_init (&sem_id, 0, 1);
pthread_create (&id1,null,thread_one_fun, NULL);
pthread_create (&id2,null,thread_two_fun, NULL);
Pthread_join (id1,null);
Pthread_join (id2,null);
Sem_destroy (&sem_id);
printf ("main,,, \ n");
return 0;
}

///above the routine, exactly which line enters upgradeable applies to the semaphore resource, which is random. If you want a specific order, you can use 2 semaphores//to achieve it. For example, the following routine is thread 1 execution, and thread 2 continues until the end.
#include <pthread.h>
#include <semaphore.h>
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
int number;//protected global variable
sem_t sem_id1, Sem_id2;
void* thread_one_fun (void *arg)
{
sem_wait (&SEM_ID1);
printf ("Thread_one has the semaphore\n");
number++;
printf ("number =%d\n", number);
Sem_post (&SEM_ID2);
}

void* thread_two_fun (void *arg)
{
sem_wait (&SEM_ID2);
printf ("Thread_two has the semaphore \ n");
number--;
printf ("number =%d\n", number);
Sem_post (&SEM_ID1);
}

int main (int argc,char *argv[])
{
Number = 1;
pthread_t id1, Id2;
sem_init (&sem_id1, 0, 1);//Idle
sem_init (&sem_id2, 0, 0);//Busy
pthread_create (&id1,null,thread_one_fun, NULL);
pthread_create (&id2,null,thread_two_fun, NULL);
Pthread_join (id1,null);
Pthread_join (id2,null);
Sem_destroy (&SEM_ID1);
Sem_destroy (&SEM_ID2);
printf ("main,,, \ n");
return 0;
}

/ * Build two threads, each of these two threads increments its own integer variable i from 1 to 100, and controls the incremental process through the semaphore, that is, the difference between these two integer variables cannot exceed 5. */
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
#include <stdio.h>
#define MAX
sem_t sem1,sem2;
void* th_fn1 (void* Arg)
{
int i;
For (i = 0; i < MAX; ++i)
{
sem_wait (&sem1);
printf ("Numberin Thread1 is%d\n", i);
Sem_post (&SEM2);
}
Pthread_exit ((void*) "thread1exit\n");
}
void* th_fn2 (void* Arg)
{
int i;
For (i = 0; i < MAX; ++i)
{sem_wait (&sem2);
printf ("number in Thread2 is%d\n", i);
Sem_post (&sem1);
}
Pthread_exit ((void*) "thread2exit\n");
}
int main (void)
{
Void*tret;
Sem_init (&sem1,0,5);
Sem_init (&sem2,0,5);
pthread_t Tid1,tid2;
pthread_create (&tid1,null,th_fn1,null);
pthread_create (&tid2,null,th_fn2,null);
Pthread_join (Tid1,&tret);
Pthread_join (Tid2,&tret);
Sem_destroy (&sem1);
Sem_destroy (&SEM2);
return 0;
}

The unknown semaphore is synchronized between multiple threads