#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include </usr/include/semaphore.h>


sem_t mutex;

int count = 0;

void * ThreadAdd(void * a)
{
        int i=10, tmp;

        while(1){
                printf("this is in the thread %d and i is %d \n" ,count,i);
                sem_wait(&mutex);
        }
}

int main(int argc, char * argv[])
{
        pthread_t tid1, tid2;
        sem_init(&mutex, 0, 1);
        int i=10;

        if(pthread_create(&tid1, NULL, ThreadAdd, NULL)){
                printf("\n ERROR creating thread 1");
                exit(1);
        }


        while (1){
                printf("Enter the id please \n");
                scanf("%d",&count);
                sem_post(&mutex);
        }

        if(pthread_join(tid1,NULL)){
                printf("\n ERROR joining thread");
                exit(1);
        }


        pthread_exit(NULL);
}

output
------
Enter the id please
this is in the thread 0 and i is 10
this is in the thread 0 and i is 10
1
Enter the id please
this is in the thread 1 and i is 10
2
Enter the id please
this is in the thread 2 and i is 10
3
Enter the id please
this is in the thread 3 and i is 10
4
Enter the id please
this is in the thread 4 and i is 10
5
Enter the id please
this is in the thread 5 and i is 10
6
this is in the thread 6 and i is 10
Enter the id please





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my doubt is even though we have sem_wait in the thread function still why does it executes two times 

it has to execute one time and then it has to wait 

so why is it executing two times ?