file descriptors and open files

Question

I have two quick questions:

When do two file descriptors point to the same open file ?

When do two open files point to the same inode ?

Also, if you happen to have some good documentation with graphs explaining this, i'll be very grateful if you show me the link to it :)

Thanks!

Answer 1

You can open as many file descriptors to a single file as you like - just call open() a few times. It's common for operating systems to allow a file either to be opened for reading (by as many clients as want access) or for reading and writing (but by only a single client).

Two files in a filesystem could point to the same inode if they were hard links to the same file.