shm_sample_write.c

来自「linux下进程间通讯列子」· C语言 代码 · 共 79 行

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <errno.h>
#include <stdio.h>
#include <sys/sem.h>
#define SHARE_SIZE 2048

union semun 
{
   int val;                  /* value for SETVAL */
   struct semid_ds *buf;     /* buffer for IPC_STAT, IPC_SET */
   unsigned short *array;    /* array for GETALL, SETALL */
                                       /* Linux specific part: */
   struct seminfo *__buf;    /* buffer for IPC_INFO */
};

int sem_creat()
{
	int semid;
	semid=semget((key_t)8972,1,IPC_CREAT|0666);
	return semid;
}

void sem_setval(int semid)
{
     union semun semun_info;
     semun_info.val=1;
     semctl(semid,0,SETVAL,semun_info);		
}

void sem_p(int semid)
{
	struct sembuf  sem_buf;
	sem_buf.sem_num=0;
	sem_buf.sem_op=-1;
	sem_buf.sem_flg=SEM_UNDO;
	semop(semid,&sem_buf,1);
}

void sem_v(int semid)
{
	struct sembuf  sem_buf;
        sem_buf.sem_num=0;
        sem_buf.sem_op=1;
        sem_buf.sem_flg=SEM_UNDO;
        semop(semid,&sem_buf,1);
}

struct student 
{
	char name[30];
	int age;
};

int main(int argc,char *argv[])
{
	int shmid;
	int semid;
	int i=0;
	struct student *stu_info;
	void *shm_addr=NULL;
	//semid=sem_creat();
	shmid=shmget((key_t)5566,SHARE_SIZE,IPC_CREAT|0666);
	shm_addr=shmat(shmid,NULL,0);
	stu_info=(struct student*)shm_addr;
	strcpy(stu_info->name,"cn0803 hzq");
	//sem_p(semid);
	stu_info->age++;
	printf("stu age %d\n",stu_info->age);
	sleep(1);
	stu_info->age++;
	printf("stu age %d\n",stu_info->age);
	sleep(1); 
	//sem_v(semid);
	return 0;
}