sem.c

liunx下的shell实现；进程、线程同步的实现；I/O系统调用的比较（mmap）——操作系统的课程设计

#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/sem.h>
union semun{
  int val;
  struct semid_ds *buf;
  unsigned short *array;
};
int get_sem_val(int sid,int semnum)
{
  return (semctl(sid,semnum,GETVAL,0));
}
void set_a_sem(int sid,int semnum,int initval)
{
  union semun semopts;
  semopts.val=initval;
  semctl(sid,semnum,SETVAL,semopts);
}
void set_all_sem(int sid,unsigned short val_array[])
{
  union semun semopts;
  semopts.array=val_array;
  semctl(sid,0,SETALL,semopts);
}
int rm_sem(int sid)
{
  return(semctl(sid,0,IPC_RMID,0));
}
int sem_p(int sem_id,int id)
{
  struct sembuf sb;
  sb.sem_num=id;
  sb.sem_op=-1;
  sb.sem_flg=SEM_UNDO;
  if(semop(sem_id,&sb,1)==-1)
    {
      printf("semaphore_p failed");
      return 0;
    }
  return 1;
}
int sem_all_p(int sem_id,int id_1,int id_2)
{
  struct sembuf sb[2];
  sb[0].sem_num=id_1;
  sb[0].sem_op=-1;
  sb[0].sem_flg=SEM_UNDO;
  sb[1].sem_num=id_2;
  sb[1].sem_op=-1;
  sb[1].sem_flg=SEM_UNDO;
  if(semop(sem_id,sb,2)==-1)
    {
      printf("semaphore_p failed");
      return 0;
    }
  return 1;
}
int sem_v(int sem_id,int id)
{
  struct sembuf sb;
  sb.sem_num=id;
  sb.sem_op=1;
  sb.sem_flg=SEM_UNDO;
  if(semop(sem_id,&sb,1)==-1)
    {
      printf("semaphore_p failed");
      return 0;
    }
  return 1;
}
int sem_all_v(int sem_id,int id_1,int id_2)
{
  struct sembuf sb[2];
  sb[0].sem_num=id_1;
  sb[0].sem_op=1;
  sb[0].sem_flg=SEM_UNDO;
  sb[1].sem_num=id_2;
  sb[1].sem_op=1;
  sb[1].sem_flg=SEM_UNDO;
  if(semop(sem_id,sb,2)==-1)
    {
      printf("semaphore_p failed");
      return 0;
    }
  return 1;
}