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);
}
}