HP 3000 Manuals HP 3000 Manuals
Providing Communication Between Processes Different processes can pass information among themselves using a special feature of the operating system, referred to as Interprocess Communication (IPC). Large tasks that have been broken into independent processes can use IPC to synchronize their actions and exchange data with other processes. There are several ways you can implement IPC on MPE XL: * Using file system intrinsics and message files * Using session-level variables and Job Control Words (JCWs) * Using process management mail intrinsics The file system intrinsics HPFOPEN,FOPEN,FREAD,and FWRITE provide the most powerful method of performing IPC. These intrinsics can be used to communicate between any user process; the processes do not need to be in the same process tree, or running in the same job or session. Processes executing in the same job or session can use a session-level variable or JCW to pass smaller amounts of data more efficiently than using message files. Some older applications use the "mail" facility to communicate between processes in the same process tree (same job or session). Each process in the process tree can use this facility to pass information between itself and either its parent or child process. For more information about using IPC features to provide communication between processes, refer to Interprocess Communication Programmer's Guide (32650-90019).