Block device information without mounting in Linux

Question

I am trying to get some information (specifically block size) of block device in linux, in C++. Is it possible to get block size of a device without mounting it and possibly

Answer 1

You want to use ioctl, in particular BLKSSZGET.

Quoting linux/fs.h:

#define BLKSSZGET  _IO(0x12,104)/* get block device sector size */

Untested example:

#include 
#include 

int fd = open("/dev/sda");
size_t blockSize;
int rc = ioctl(fd, BLKSSZGET, &blockSize);