Direct access to hard disk with no FS from C program on Linux

Question

I want to access the whole hard disk directly from a C program. There\'s no FS on it and never\'s gonna be one.

I just want to open /dev/sda (for example) and do I

Answer 1

As mentioned elsewhere, under *NIX systems, block devices like /dev/sda can be accessed as plain files. Note that if file system is mounted from the device, opening it as file for writing would fail.

If you want to play with block devices, I would advise to first use the loop device, which presents a plain file as a block device. For example:

dd if=/dev/zero of=./loop_file_10MB bs=1024 count=10K
losetup /dev/loop0 $PWD/loop_file_10MB

After that, /dev/loop0 would behave as if it was a block device, but all information written would be stored in the file.