What is inter-process communication? How many methods are there for inter-process communication in Linux?

How many methods are there for Linux inter-process communication? The so-called inter-process communication is to spread or exchange information between different processes. Linux supports a variety of inter-process communication mechanisms. Common methods are as follows ：

Interprocess communication (IPC, Interprocess
communication) is a set of programming interfaces that allow programmers to coordinate different processes so that they can run simultaneously in an operating system and transfer and exchange information with each other. This enables a program to handle many user requests at the same time. Because even if only one user issues a request, it may cause multiple processes to run in an operating system, and the processes must talk to each other. The IPC interface provides this possibility. Each IPC method has its own advantages and limitations, and generally it is uncommon for a single program to use all IPC methods.

　1. Unnamed pipe communication

Pipeline is a half-duplex communication method that can only be used between related processes, and data flows in one direction.

　2. High*pipeline communication

High * pipeline (popen) is a way to start another program as a new process in the current program process, so that the new program becomes a child process of the current program. This method is called high * pipeline method.

　3. Famous channel communication

Named pipe: Named pipe is also a half-duplex communication method, but it allows communication between unrelated processes.

　4. Message queue communication

Message queue (message
queue): The message queue is a linked list of messages, which is stored in the kernel and identified by the message queue identifier. The message queue overcomes the problem of less signal transmission information and the pipe can only carry unformatted bytes. Disadvantages such as limited stream and buffer size.

　5. Semaphore communication

Semaphore: A semaphore is a counter that can be used to control the access of multiple processes to shared resources. It is often used as a lock mechanism to prevent other processes from accessing the resource when a process is accessing the shared resource. . Therefore, it is mainly used as a means of synchronization between processes and between different threads within the same process.

　6. Signal

Signal (sinal): Signal is a relatively complex communication method used to notify the receiving process that an event has occurred.

　7. Shared memory communication

Shared memory (shared
memory): Shared memory is to map a section of memory that can be accessed by other processes. This shared memory is created by one process, but can be accessed by multiple processes. Shared memory is the fastest IPC method and is specially designed to address the inefficiency of other inter-process communication methods. It is often used in conjunction with other communication mechanisms, such as semaphores, to achieve synchronization and communication between processes.

　8. Socket communication

Socket: Socket is also an inter-process communication mechanism. Unlike other communication mechanisms, it can be used for process communication between different machines.

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