总结 共享内存

http://tonybai.com/2005/09/23/apr-shmem/

    匿名共享内存：

【1】

int N=1024; //大小

char *p = mmap(NULL, N, PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED,-1,0);

p[0]='A';

p[a]='B';

...

mummap(p,N);

【2】

int N=1024; //大小

int fd=open("/dev/zero", O_RDWR);

char *p = mmap(NULL, N, PROT_READ|PROT_WRITE, MAP_SHARED,fd,0);

...

munmap(p,N);

【3】

int N=1024;

int id=shmget(IPC_PRIVATE,N,0666);

char *p=shmat(id,NUL,0);

...

shmdt(p);  //解除

shmctl(id,IPC_RMID,NULL); //拆除

有名共享内存：

【1】

int fd = open("abc", O_RDWR|O_CREAT|O_TRUNC, 0666);  或  un_link("abc");int fd = open("abc", O_RDWR|O_CREAT|O_EXCL, 0666);

ftruncate(fd,1024);

char *p = map(NULL,1024,PROT_READ|PROT_WRITE, MAP_SHARED, fd,0);

p[0]=...

munmap(p,1024);

un_link("abc");

【2】

int fd = shm_open("abc", O_RDWR|O_CREAT|O_TRUNC, 0666);  或  shm_unlink("abc");int fd = shm_open("abc", O_RDWR|O_CREAT|O_EXCL, 0666);

ftruncate(fd,1024);

char *p = map(NULL,1024,PROT_READ|PROT_WRITE, MAP_SHARED, fd,0);

p[0]=...

munmap(p,1024);

unlink("abc");

【3】

key_t kt=ftok("abc",0);

int id=shmget(kt,1024,IPC_CREAT|0666);

char *p=shmat(id,NULL,0);

....

shmdt(p);

shmctl(id,IPC_RMID,NULL);