帮忙写个Linux下从指定fd获取共享内存并返回其fd的代码
时间: 2024-03-08 15:50:46 浏览: 14
好的,以下是一个简单的示例代码,可以从给定的文件描述符(fd)获取共享内存并返回其文件描述符:
```c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
int get_shared_mem_fd(int fd)
{
int shm_fd = -1;
void *addr;
// Map the shared memory to the process's address space
addr = mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (addr == MAP_FAILED) {
perror("Failed to map shared memory");
exit(1);
}
// Get the file descriptor for the shared memory
shm_fd = memfd_create("shared_mem", 0);
if (shm_fd < 0) {
perror("Failed to create shared memory file descriptor");
exit(1);
}
// Copy the contents of the shared memory to the file descriptor
write(shm_fd, addr, sizeof(int));
// Unmap the shared memory
munmap(addr, sizeof(int));
return shm_fd;
}
int main(int argc, char *argv[])
{
int fd = -1;
int shm_fd = -1;
// Open the file descriptor for the shared memory
fd = open("/dev/shm/shared", O_RDWR);
if (fd < 0) {
perror("Failed to open shared memory");
exit(1);
}
// Get the file descriptor for the shared memory
shm_fd = get_shared_mem_fd(fd);
if (shm_fd < 0) {
perror("Failed to get shared memory file descriptor");
exit(1);
}
// Use the shared memory file descriptor as needed...
printf("Shared memory file descriptor: %d\n", shm_fd);
// Close the file descriptors
close(shm_fd);
close(fd);
return 0;
}
```
此代码假设您要从名为 `/dev/shm/shared` 的设备获取共享内存。请根据需要修改设备名称和其他参数。