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, "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.