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cposixipcubuntu-18.04

How can I create a POSIX shared message queue without it created as root access only?

I am creating a message queue using the POSIX mqueue API:

    mq_open("/myqueue", O_CREAT | O_WRONLY, O_WRONLY, NULL)

I also mount the directory for the message queue objects:

su
mkdir /dev/mqueue
mount -t mqueue none /dev/mqueue
exit

When I run my program, the message queue appears in /dev/mqueue with permissions:

---------x

I cannot interact with this message queue, and it does not show up with the ipcs command.

How can I create a POSIX message queue to be used by a user-level application in Ubuntu 18.04?

Solution

  • Your arguments to the function are wrong. You're passing O_WRONLY as the mode, but it's a flag, just like the other O_*. Instead you should do:

    mq_open("/myqueue", O_CREAT | O_WRONLY, 0600, NULL);

    or some other file access mode that you want (0600 = rw-------).