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.