ipcmk

Create a shared memory segment

$ ipcmk -M [segment_size_in_bytes]

$ ipcmk -S [element_size]

$ ipcmk -Q

$ ipcmk -M [segment_size] -p [0644]

ipcmk [options]

ipcmk creates System V IPC (Inter-Process Communication) resources. These resources allow processes to communicate and synchronize: shared memory enables direct data sharing, semaphores coordinate access to resources, and message queues enable asynchronous messaging.
Created resources are identified by a key and ID, which can be viewed with ipcs and removed with ipcrm. Resources persist until explicitly removed or system reboot.

-M, --shmem SIZE

Create shared memory segment of specified size in bytes

Create semaphore set with specified number of elements

Create message queue

Set permissions (octal, default 0644)

System V IPC has kernel limits on the number and size of resources. Resources are not automatically cleaned up when creating processes exit. Modern applications often prefer POSIX IPC or other mechanisms.

System V IPC was introduced in AT&T UNIX System V in the early 1980s. While older than POSIX alternatives, it remains widely used and supported across Unix-like systems.

ipcs(1), ipcrm(1), lsipc(1)