/* This program initializes semaphores on kiwi (and sister machines) */
/* First it gets 'em (they come set to 0 (block) "from the factory") */
/* and shows their values. Then, they're all set to 1. They get      */
/* their values printed again. Then sleep for 5 seconds (you might   */
/* want to suspend and do an ipcs to see the semaphore). Finally,    */
/* semaphore set is removed from the system.			     */
/* YOU MUST BE SURE YOUR SEMAPHORES ARE REMOVED FROM THE SYSTEM AFTER*/
/* YOU USE THIS PROGRAM OR ANY OTHER THAT USES SEMAPHORES. TO DO SO  */
/* FROM THE COMMAND LINE, ENTER ipcs TO GET THE SEMAPHORE SET ID, AND*/
/* THEN ISSUE 	ipcrm -s <semaphore set id> . Do ipcs to double check*/
#include <stdio.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 */

union semun {
  int val;
  struct semid_ds* buf;
  unsigned short  *array;  /* Array for GETALL, SETALL */
  #if defined(_linux_)
    struct seminfo  *__buf;  /* Buffer for IPC_INFO      */
  #endif
} arg;

void PrintSems(semid,NumSems)
int semid,NumSems;
{int i;
 short *values;
 // Have to allocate space for array of short NOTE: man page says you don't.
 Values=(short *)malloc(sizeof(short)*NumSems);
 semctl(semid,NULL,GETALL,&values);   // don't have to use union here?
 fprintf(stderr,"Semaphore Values ");
 for (i=0;i<NumSems;i++)
  fprintf(stderr,"#%d. %d  | ",i,values.array[i]);
 fprintf(stderr,"\n");
}

main(argc,argv)
int argc;
char *argv[];
{int key, semid, i, NumSems;
 struct semid_ds s;
 ushort *values;
 if (argc!=2) {
  fprintf(stderr,"Form: semdemo <# of semaphores>\n");
  exit(1);
 }
 NumSems=atoi(argv[1]);
 arg.array=(ushort *)malloc(NumSems*sizeof(ushort));
 key=getuid(); 
 semid = semget(key, NumSems, 0600|IPC_CREAT);
 semctl(semid,0,IPC_STAT,&s);
 fprintf(stderr,"Semaphore id %d: ", semid);
 PrintSems(semid,NumSems); 
 for (i=0;i<NumSems;i++)
  *(arg.array+i)=1;
 printf("Set all to 1 at once\n");
 semctl(semid,NULL,SETALL,arg);
 PrintSems(semid,NumSems); 
 for (i=0;i<NumSems;i++)
  *(arg.array+i)=0;
 printf("Set all back to 0 at once\n");
 semctl(semid,NULL,SETALL,arg);
 PrintSems(semid,NumSems); 
 sleep(1);
 printf("And, remove the set......\n");
 semctl(semid,0,IPC_RMID,0);
}