Prerequisite : Inter Process Communication
A message queue is a linked list of messages stored within the kernel and identified by a message queue identifier. A new queue is created or an existing queue opened by msgget().
New messages are added to the end of a queue by msgsnd(). Every message has a positive long integer type field, a non-negative length, and the actual data bytes (corresponding to the length), all of which are specified to msgsnd() when the message is added to a queue. Messages are fetched from a queue by msgrcv(). We don’t have to fetch the messages in a first-in, first-out order. Instead, we can fetch messages based on their type field.
All processes can exchange information through access to a common system message queue. The sending process places a message (via some (OS) message-passing module) onto a queue which can be read by another process. Each message is given an identification or type so that processes can select the appropriate message. Process must share a common key in order to gain access to the queue in the first place.
System calls used for message queues:
ftok(): is use to generate a unique key. msgget(): either returns the message queue identifier for a newly created message queue or returns the identifiers for a queue which exists with the same key value. msgsnd(): Data is placed on to a message queue by calling msgsnd(). msgrcv(): messages are retrieved from a queue. msgctl(): It performs various operations on a queue. Generally it is use to destroy message queue.
MESSAGE QUEUE FOR WRITER PROCESS
MESSAGE QUEUE FOR READER PROCESS
- Message Passing in Java
- Message encryption and decryption using UDP server
- Print colored message with different fonts and sizes in C
- Message based Communication in IPC (inter process communication)
- __builtin_inf() functions of GCC compiler
- Journaling or write-ahead logging
- File System Consistency Checker (FSCK)
- Count substrings that contain all vowels | SET 2
- How can we use Comma operator in place of curly braces?
- Basic Code Optimizations in C
- Constants vs Variables in C language
- Sum of an array using MPI
- 8086 program to convert a 16 bit decimal number to Hexadecimal
- 8086 program to find GCD of two numbers and print the GCD
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.