IPC--共享内存 Share Memory 实例(shmget shmat shmdt shmctl)

/*
 * writeShareM.c
 *
 *  Created on: 2011-11-20
 *      Author: snape
 */

#include <stdio.h>
#include <sys/shm.h>
#include <unistd.h>
#include <string.h>

int main(int argc, char **argv) {
	void say(int, char *);

	int shmid;
	int i = 0;
	char *pshm;
	char buf[1024];
	//shmget第二个参数指定创建的共享内存的大小
	say((shmid = shmget(1000, 1024 * 10, 0666 | IPC_CREAT)) < 0,
			"create share memory");
	
	//shmat for share memory attach
	//第二个参数和第三个参数指定要映射得物理内存地址
	//通常设为是 NULL 0 ，表示要映射得物理内存地址是进程空间得首地址
	say((pshm = (char *) shmat(shmid, 0, 0)) == NULL, "attch shm");

	printf("input node 0-9\n");
	scanf("%d", &i);
	printf("node is %d\n", i);

	memset(buf, 0, sizeof(buf));

	printf("input data\n");

	scanf("%s", buf);

	memcpy(pshm + i * 1024, buf, 1024);
	
	//取消对pshm物理地址得映射（进程结束系统会释放共享内存对物理地址得映射) shmdt for share memory detach
	//调用该函数，不会删除共享内存对象，而是将该共享内存对象得链接数减1。
	shmdt(pshm);

	return 0;
}

void say(int flag, char *str) {
	if (flag) {
		fprintf(stderr, "[%s] error\n",str);
	} else {
		fprintf(stderr, "[%s] success\n",str);
	}
}

/*
 * rShareM.c
 *
 *  Created on: 2011-11-20
 *      Author: snape
 */

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/shm.h>

int main(int argc, char **argv) {
	void say(int, char *);
	int i;
	char *pshm;
	char buf[1024];
	int shmid;

	say((shmid = shmget(1000, 10240, 0666 | IPC_CREAT)) < 0,
			"create share memory");
	say((pshm = (char *) shmat(shmid, 0, 0)) == NULL, "attach shm");

	printf("input node 0-9\n");
	scanf("%d", &i);
	printf("node is %d\n",i);


	memset(buf, 0, 1024);
	memcpy(buf,pshm+i*1024,1024);
	fprintf(stderr,"data [%s]\n",buf);
	shmdt(pshm);
	return 0;
}
void say(int flag, char *str) {
	if (flag) {
		fprintf(stderr, "[%s] error\n", str);
	} else {
		fprintf(stderr, "[%s] success\n", str);
	}
}