shmctl

shmctl id, cmd, arg

Calls the System V IPC system call, shmctl(2), for performing operations on shared memory segments. If cmd is &IPC_STAT, then arg must be a variable that will hold the returned shmid_ds structure. The function returns like ioctl: the undefined value for error, "0 but true" for zero, or the actual return value otherwise. On error, it puts the error code into $!. Before calling, you should say:

require "ipc.ph";
require "shm.ph";

This function is available only on machines supporting System V IPC.