#include <stdio.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/sem.h>#define LINUX_ENV#ifdef LINUX_ENV#define _GNU_SOURCE#endifunion semun{	int val;	struct semid_ds * buf;	unsigned short int * array;	struct seminfo * __buf;};int main(void){	key_t key;	int proj_id;	int semid;	int nsems;	union semun arg;	struct semid_ds buffer;	proj_id=2;	key=ftok("/home/program",proj_id);	if(key==-1){		perror("cannot generate the IPC key");		return 1;	}		nsems=2;	semid=semget(key,nsems,IPC_CREAT | 0660);	if(semid==-1){		perror("cannot create semaphore set resource");		return 1;	}		arg.buf=&buffer;	if(semctl(semid,0,IPC_STAT,arg)==-1){		perror("cannot get semaphore set info");		return 1;	}	printf("=======semphore set info========\n");	printf("effective user id : %d \n",buffer.sem_perm.uid);	printf("effective group id: %d \n",buffer.sem_perm.gid);	printf("semaphore set's creator user id : %d \n",buffer.sem_perm.cuid);	printf("semaphore set's creator group id : %d \n",buffer.sem_perm.cgid);	printf("access mode : %x\n",buffer.sem_perm.mode);       	//special parameter, only for linux#ifdef LINUX_ENV	if(semctl(semid,0,SEM_INFO,arg)==-1){		perror("cannot get semphore set info");		return 1;	}	struct seminfo* sem_info;	sem_info=(struct seminfo *)(&buffer);	printf("Max. # of semaphore sets: %d \n",sem_info->semmni);	printf("Max. # of semaphores in all semaphore sets: %d \n",sem_info->semmns);	printf("Max. # of semaphores in a set: %d \n",sem_info->semmsl);	printf("Max. # of operations for semop(): %d \n",sem_info->semopm);	printf("size of struct sem_undo: %d \n",sem_info->semusz);	printf("Max. value that can be recorded for semaphore adjustment (SEM_UNDO): %d \n",sem_info->semaem);#endif}