#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
#define NumSems 3

void PrintSems(semid)
int semid;
{int i;
 ushort Values[NumSems];
 semctl(semid,0,GETALL,Values);
 fprintf(stderr,"Semaphore Values ");
 for (i=0;i<NumSems;i++)
  fprintf(stderr,"#%d. %d  | ",i,Values[i]);
 fprintf(stderr,"\n");
}

main()
{int key, semid, i;
 extern int errno;
 ushort Array[NumSems];
 struct sembuf s[2];
 key=getuid(); 
 semid = semget(key, NumSems, 0600|IPC_CREAT);
 fprintf(stderr,"Semaphore id %d Values:", semid);
 PrintSems(semid); 
 for (i=0;i<NumSems;i++) Array[i]=1;
 Array[1]=0;
 semctl(semid,NULL,SETALL,Array);
 PrintSems(semid); 
 s[0].sem_num=0;
 s[0].sem_op=-1;
 s[0].sem_flg=0;
 s[1].sem_num=1;
 s[1].sem_op=-1;
 s[1].sem_flg=IPC_NOWAIT;
 semop(semid,s,2);
 PrintSems(semid); 
 if (errno==EAGAIN) fprintf(stderr,"Error Number is EAGAIN: #%d\n"); 
 else if (errno==0) fprintf(stderr,"No error\n");
 sleep(5);
 semctl(semid,0,IPC_RMID,0);
}