共享内存是进程间通讯的一种方式,PostgreSQL使用共享内存缓存数据以及各种数据结构. 下面是演示代码,逻辑很简单,自行参考代码注释. ```C /* 申请一段共享内存，父进程写入一串字符，子进程读出。 */ #include <stdio.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/types.h> #include <unistd.h> #include <stdlib.h> //1k共享内存 #define SHM_SIZE 1024 #define SHM_ID 10086 int main() { //共享内存id,子进程id int shmid, pid; //共享内存指针 char *ptr = NULL; //申请共享内存 shmid = shmget((key_t)SHM_ID, SHM_SIZE, IPC_CREAT | 0600); //映射共享内存到进程地址空间 ptr = (char *)shmat(shmid, 0, 0); printf("Attach pointer addr is %p \n", ptr); ptr = "This is shared memory!"; printf("The String of Parent Process is : %s \n", ptr); if((pid = fork()) == -1) { perror("fork process error!"); exit(0); } else if(!pid) { printf("Child Process PID is : %d,String is %s \n", pid,ptr); exit(0); }else{ sleep(1); //解除映射 shmdt(ptr); //删除共享内存 shmctl(shmid, IPC_RMID, 0); } return 0; } ``` 运行输出 ``` [pg12@localhost ipc]$ gcc -std=c11 -o fork fork.c In file included from fork.c:7:0: /usr/include/sys/ipc.h:24:3: warning: #warning "Files using this header must be compiled with _SVID_SOURCE or _XOPEN_SOURCE" [-Wcpp] # warning "Files using this header must be compiled with _SVID_SOURCE or _XOPEN_SOURCE" ^ [pg12@localhost ipc]$ ./fork Attach pointer addr is 0x7f61ffb6b000 The String of Parent Process is : This is shared memory! Child Process PID is : 0,String is This is shared memory! [pg12@localhost ipc]$ ```