msgctl

msgctl id, cmd, arg

Calls the msgctl system call, which is used to perform different control operations on IPC message queues. See the msgctl documentation on your system for details. If cmd is &IPC_STAT, then arg must be a variable that will hold the returned msqid_ds structure. The return values work like those of fnctl: 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 "msg.ph";

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