outshm.h

一个编程中常用的PV操作(生产者—消费者)的c语言的demo

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <string.h>

struct exchange
{
	char buf[BUFSIZE+80];//要交换的数据
	int seq;            //客户填入的顺序号
}
int open_semaphore_set(key_t, int);
void init_a_semaphore(int, int, int);
int semaphore_P(int);
int semaphore_V(int);
//创建/打开共享存储段，连接它到用户地址空间，返回它在用户空间的地址
unsigned char *shminit(key_t key)
{
	int shmid;
	unsigned char *retval;
	if ((shmid = shmget(key, sizeof(struct exchange),0666|IPC_CREAT)) == -1)
	{
		prinf("shmget error!\n");
		exit(0);
	}
	if ((retval = shmat(shmid,(unsigned char *)0, 0)) == (unsigned char *)-1)
	{
		prinf("shmat error!\n");
		exit(0);
	}
	return retval;
}