Is there any way such that a writer process after sending a mesage to message queue using mq_send(), multiple reader processes can read the message using mq_receive(). I expect 1 write to mq and 1 read from mq, the message is lost.
So I just want to know if my understanding is wrong. Is there any way so that a single writer and multiple reader processes can communicate using posix message queues.
Yes your understanding is correct. You can't do this reliably with POSIX message queues. If you want to communicate the same message to different threads/processes reliably you should use a different queue for each reader.
You can do this if you switch to SYSV message queues. Msgsnd() and msgrcv() can manipulate the message type field of a message in some agreed upon protocol. For instance the writer process will make the message type of the message the PID of the reader process; and the reader process will request to read only messages of that message type. Note that this still requires the writer to write a message for each reader process.
