Get message queue ID from Key provided

Question

I have a key for message queue inter process communication, say key_t = 10. I want to get the queue ID if message queue already exist with key value 10. Currently I am using below code to find the queue is exist or not using return error

msgget((key_t)10,IPC_EXCL|IPC_CREAT|0777)

but I want to get queue ID and need to close it.

Answer 1

You can use msgget without using IPC_EXCL flag to get existing message queue identifier.

mid = msgget((key_t)10, 0);

Then, using that identifier you can use remove the message queue by using msgctl with IPC_RMID flag.

EDIT:

key_t ftok(char *pathname, char proj_id);