有两种方法：shmget和mmap。我将讨论mmap，因为它更现代，更灵活，但是如果您想使用旧式工具，可以看看man shmget（或本教程）。
该mmap()函数可用于分配具有高度可自定义参数的内存缓冲区，以控制访问和权限，并在必要时通过文件系统存储支持它们。
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
void* create_shared_memory(size_t size) {
// Our memory buffer will be readable and writable:
int protection = PROT_READ | PROT_WRITE;
// The buffer will be shared (meaning other processes can access it), but
// anonymous (meaning third-party processes cannot obtain an address for it),
// so only this process and its children will be able to use it:
int visibility = MAP_SHARED | MAP_ANONYMOUS;
// The remaining parameters to `mmap()` are not important for this use case,
// but the manpage for `mmap` explains their purpose.
return mmap(NULL, size, protection, visibility, -1, 0);
}
下面是一个示例程序，该程序使用上面定义的功能来分配缓冲区。父进程将编写一条消息，进行分叉，然后等待其子进程修改缓冲区。这两个进程都可以读取和写入共享内存。
#include <string.h>
#include <unistd.h>
int main() {
char parent_message[] = "hello"; // parent process will write this message
char child_message[] = "goodbye"; // child process will then write this one
void* shmem = create_shared_memory(128);
memcpy(shmem, parent_message, sizeof(parent_message));
int pid = fork();
if (pid == 0) {
printf("Child read: %s\n", shmem);
memcpy(shmem, child_message, sizeof(child_message));
printf("Child wrote: %s\n", shmem);
} else {
printf("Parent read: %s\n", shmem);
sleep(1);
printf("After 1s, parent read: %s\n", shmem);
}
}
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