msgcomm

msgcomm [-t type] [-n] source_qid dest_qid

source_qid
    The numeric identifier of the source message queue from which messages will be copied.

dest_qid
    The numeric identifier of the destination message queue to which messages will be copied.

-t type
    Copies only messages of the specified type. If this option is omitted, all messages are copied, regardless of their type.

-n
    Specifies that messages should not be removed from the source_qid after being copied. By default, messages are removed from the source queue.

The msgcomm command is a utility for interprocess communication (IPC) in Linux, specifically designed for System V message queues. It facilitates the copying of messages from a specified source message queue to a destination message queue. This can be useful for various scenarios such as migrating messages between applications, creating backups of queue contents, or staging messages for further processing.
By default, messages are removed from the source queue after being copied, effectively moving them. However, an option is available to only copy the messages, leaving the originals intact in the source queue. It also allows filtering messages by type, enabling selective message transfer.

msgcomm requires appropriate read permissions on the source queue and write permissions on the destination queue.
Message queue identifiers (QIDs) are ephemeral and unique only while the queue exists within the kernel.
Copying a large number of messages can temporarily consume significant system resources.
The destination queue must already exist for the operation to succeed; msgcomm does not create new queues.

msgcomm exits with a status of 0 on success. On failure, it exits with -1 and prints an informative error message to standard error, indicating the reason for the failure (e.g., invalid queue IDs, permission denied, or resource limitations).

This command is typically used by system administrators or developers for debugging, managing, or migrating IPC message queue contents. It's a low-level utility and not commonly part of application-level logic directly.

msgcomm is part of the System V IPC utilities, a set of features dating back to AT&T System V Unix, providing fundamental mechanisms for interprocess communication including message queues, semaphores, and shared memory. These utilities have been a standard component of Unix-like operating systems, including Linux, for decades, ensuring compatibility and robust IPC capabilities.

ipcs(1), ipcrm(1), ipcmk(1), msgget(2), msgsnd(2), msgrcv(2), msgctl(2), ipc(5)