What is the point of having a key_t if what will be the key to access shared memory is the return value of shmget()?
- by devoured elysium
When using shared memory, why should we care about creating a key
key_t ftok(const char *path, int id);
in the following bit of code?
key_t key;
int shmid;
key = ftok("/home/beej/somefile3", 'R');
shmid = shmget(key, 1024, 0644 | IPC_CREAT);
From what I've come to understand, what is needed to access a given shared memory is the shmid, not the key. Or am I wrong? If what we need is the shmid, what is the point in not just creating a random key every time?
Edit
@link text one can read:
What about this key nonsense? How do
we create one? Well, since the type
key_t is actually just a long, you can
use any number you want. But what if
you hard-code the number and some
other unrelated program hardcodes the
same number but wants another queue?
The solution is to use the ftok()
function which generates a key from
two arguments.
Reading this, it gives me the impression that what one needs to attach to a shared-memory block is the key. But this isn't true, is it?
Thanks
