12.30

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


int flag = 1;


void * thread_function(void * arg);


int main()
{
int ret;
    pthread_t tid;
void * thread_result;
int count = 1;


ret = pthread_create(&tid,NULL,thread_function,NULL);


if(ret != 0)
{
perror("thread create failed!\n");
exit(EXIT_FAILURE);
}


while(count++ < 10)
{
if(flag == 1)
{
printf("1");
flag = 2;
}
else
{
sleep(1);
}
}


printf("\nwaiting for thread to finish...\n");


ret = pthread_join(tid,&thread_result);


if(ret != 0)
{
perror("thread join failed!\n");
exit(EXIT_FAILURE);
}

    return 0;
}


void * thread_function(void *arg)
{
int count = 1;
while(count++ < 10)
{
if(flag == 2)
{
printf("2");
flag = 1;
}
sleep(1);
}
}