ipc unit

Unix Inter Process Communication functionality.

This document describes the IPC unit for Free Pascal. It was written for Linux by Michael Van Canneyt. It gives all the functionality of System V Inter-Process Communication: shared memory, semaphores and messages. It works only on the Linux operating system.

Many constants here are provided for completeness only, and should under normal circumstances not be used by the programmer.

Classes and records

`TIPC_Perm`	record	Record used in all IPC systems to specify the permissions.
`TMSG`	record	Record used in the handling of message queues. Do not use directly.
`TMSGbuf`	record	Generic message data record.
`TMSQid_ds`	record	Record returned by the call, contains all data about a message queue.
`TSEMbuf`	record	Record used in call.
`TSEMid_ds`	record	Structure returned by the call, contains all data of a semaphore.
`TSEMun`	record	Record used in call.
`TSHM_info`	record
`TShmid_ds`	record	Record used in the call to set or retrieve settings for shared memory.
`TSHMinfo`	record	Record used by the shared memory system, Do not use directly.

Procedures and functions

`ftok`	function	Create token from filename.
`msgctl`	function	Perform various operations on a message queue.
`msgget`	function	Return message queue ID, possibly creating the queue.
`msgrcv`	function	Retrieve a message from the queue.
`msgsnd`	function	Send a message to the message queue.
`semctl`	function	Perform various control operations on a semaphore set.
`semget`	function	Return the ID of a semaphore set, possibly creating the set.
`semop`	function	Perform semaphore operation.
`semtimedop`	function	Perform semaphore operation using timeout.
`shmat`	function	Attach a shared memory block.
`shmctl`	function	Perform control operations on a shared memory block.
`shmdt`	function	Detach shared memory block.
`shmget`	function	Return the ID of a shared memory block, possibly creating it.

Types

`key_t`	type	Alias for type.
`msglen_t`	type	Message length type.
`msgqnum_t`	type	Message queue number type.
`PIPC_Perm`	type	Pointer to record.
`PMSG`	type	Pointer to record.
`PMSGbuf`	type	Pointer to record.
`PMSQid_ds`	type	Pointer to .
`PSEMbuf`	type	Pointer to record.
`PSEMid_ds`	type	Pointer to record.
`PSEMinfo`	type	Pointer to record.
`PSEMun`	type	Pointer to record.
`PSHM_info`	type
`PShmid_DS`	type	Pointer to record.
`TKey`	type	Type returned by the key generating function.

Constants

`IPC_CREAT`	constant	Create if key is nonexistent.
`IPC_EXCL`	constant	fail if key exists.
`IPC_INFO`	constant	For ipcs call.
`IPC_NOWAIT`	constant	return error on wait.
`IPC_PRIVATE`	constant
`IPC_RMID`	constant	Remove resource.
`IPC_SET`	constant	set ipc_perm options.
`IPC_STAT`	constant	get ipc_perm options.
`MSG_EXCEPT`	constant	Internal Message control code. Do not use.
`MSG_NOERROR`	constant	Internal Message control code. Do not use.
`MSGMAX`	constant	Internal Message control code. Do not use.
`MSGMNB`	constant	Internal Message control code. Do not use.
`MSGMNI`	constant	Internal Message control code. Do not use.
`SEM_GETALL`	constant	Semaphore operation: Get all semaphore values.
`SEM_GETNCNT`	constant	Semaphore operation: Get number of processes waiting for resource.
`SEM_GETPID`	constant	Semaphore operation: Get process ID of last operation.
`SEM_GETVAL`	constant	Semaphore operation: Get current value of semaphore.
`SEM_GETZCNT`	constant	Semaphore operation: Get number of processes waiting for semaphores to reach zero.
`SEM_SEMMNI`	constant	Semaphore operation: ?
`SEM_SEMMNS`	constant	Semaphore operation: ?
`SEM_SEMMSL`	constant	Semaphore operation: ?
`SEM_SEMOPM`	constant	Semaphore operation: ?
`SEM_SEMVMX`	constant	Semaphore operation: ?
`SEM_SETALL`	constant	Semaphore operation: Set all semaphore values.
`SEM_SETVAL`	constant	Semaphore operation: Set semaphore value.
`SEM_UNDO`	constant	Constant for use in .
`SHM_LOCK`	constant	This constant is used in the call.
`SHM_R`	constant	This constant is used in the call.
`SHM_RDONLY`	constant	This constant is used in the call.
`SHM_REMAP`	constant	This constant is used in the call.
`SHM_RND`	constant	This constant is used in the call.
`SHM_UNLOCK`	constant	This constant is used in the call.
`SHM_W`	constant	This constant is used in the call.

Uses

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.