producer consumer problem

This program has a producer process , There are two consumer processes , Producer production 1-20 Of 20 Number , Two consumers retrieve data from shared memory
Code implementation :

#include<unistd.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include <sys/shm.h>
#include<sys/wait.h>
#include<stdio.h>
#include <sys/sem.h>
int i;
 union semun
  {
    
    int val;
    struct semid_ds *buf;
    unsigned short *arry;
  };
int main()
{
    
	
int semid1 =  semget((key_t)1234, 1 , 0640|IPC_CREAT);
union semun sem_union1;
 sem_union1.val = 1;
  semctl(semid1,0,SETVAL,sem_union1);
   struct sembuf sem_b;

        
    int semid2 =  semget((key_t)1235, 1 , 0640|IPC_CREAT);
	union semun sem_union2;
    sem_union2.val = 0;
    semctl(semid2,0,SETVAL,sem_union2);
    struct sembuf sem_a;
        
    int semid4  = semget((key_t)1110,1,0640|IPC_CREAT);
    union semun sem_union4;
    sem_union4.val = 1;
	semctl(semid4, 0, SETVAL,sem_union4);
	struct sembuf sem_d   ;
        
	int shmid = shmget(IPC_PRIVATE  , 1024, 0640|IPC_CREAT);
    if(shmid <0)
    {
    
        printf("error!");
	} 
	int *ptext = 0 ;
	ptext  = (int*)shmat(shmid,0,0);
	pid_t pa = 0;
	pa = fork();
	if(pa<0)
	{
    	
		printf("erorr!");
	}
    else if (pa==0)
    {
    
        	pid_t pb = 0;
        	pb = fork();
        	if(pb<0)
	{
    	
			printf("erorr!");
	}
    else if(pb ==0)
    {
    
			ptext  = (int *)shmat(shmid,0,0);
			while(1)
			{
    
			
			sleep(random()%10);
			sem_a.sem_num = 0;
            sem_a.sem_op = -1;
            sem_a.sem_flg = SEM_UNDO;
            semop(semid2, &sem_a, 1);
                     
            sem_d.sem_num = 0;
         	sem_d.sem_op = -1;
            sem_d.sem_flg = SEM_UNDO;
            semop(semid4, &sem_d, 1);
              
			printf("I am consumer1 get %d\n",ptext[i]);
			i++;
		
			
			sem_d.sem_num = 0;
            sem_d.sem_op = 1;
            sem_d.sem_flg = SEM_UNDO;
            semop(semid4, &sem_d, 1);
            
			sem_b.sem_num = 0;
            sem_b.sem_op = 1;
            sem_b.sem_flg = SEM_UNDO、
            semop(semid1, &sem_b, 1);
			}
			
        	}
        	else
      		{
    
       		
       		ptext  = (int *)shmat(shmid,0,0);
       
       		while(1){
    
       		sleep(random()%10);
       		sem_a.sem_num = 0;
            sem_a.sem_op = -1;
            sem_a.sem_flg = SEM_UNDO;
            semop(semid2, &sem_a, 1);
                       
            sem_d.sem_num = 0;
            sem_d.sem_op = -1;
            sem_d.sem_flg = SEM_UNDO;
            semop(semid4, &sem_d, 1);
       		printf("I am consumer2 get %d\n",ptext[i]);
       		i++;
       		 sem_d.sem_num = 0;
             sem_d.sem_op = 1;
             sem_d.sem_flg = SEM_UNDO;
             semop(semid4, &sem_d, 1);
                        
       	 	 sem_b.sem_num = 0;
             sem_b.sem_op = 1;
             sem_b.sem_flg = SEM_UNDO;
             semop(semid1, &sem_b, 1);
       		}
       	}
       }
        else
        {
    
           ptext  = (int *)shmat(shmid,0,0);
           struct sembuf sem_b;
           int product;
	 
           while(1){
    
           sleep(random()%10);
           struct sembuf sem_b;
           sem_b.sem_num = 0;
           sem_b.sem_op = -1;
           sem_b.sem_flg = SEM_UNDO;
           semop(semid1, &sem_b, 1);
           
           sem_d.sem_num = 0;
           sem_d.sem_op = -1;
           sem_d.sem_flg = SEM_UNDO;
           semop(semid4, &sem_d, 1);
           
           product = random()%100;
	       ptext[i] =  product;
	       printf("position is %d\n",i++);  
           printf("Producer produce %d\n ",product);
           
           sem_d.sem_num = 0;
           sem_d.sem_op = 1;
           sem_d.sem_flg = SEM_UNDO;
           semop(semid4, &sem_d, 1);
               
           sem_a.sem_num = 0;
           sem_a.sem_op = 1;
           sem_a.sem_flg = SEM_UNDO;
           semop(semid2, &sem_a, 1);
           }
        }   
	return 0	;	
}


// It just presents the core idea of the code , Didn't handle the details