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3.2.144 shmctl







This function calls the System V IPC system call, shmctl (2). If CMD is &IPC_STAT , then ARG must be a variable which 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.