pipeline communication

Before understanding the pipeline , At least we need to understand the concept of process .
The pipeline is a way for inter process communication . Say first conclusion ：

The so-called pipeline , It refers to a device used to connect a read process and a write process to realize the communication between them Shared files .

We need to understand the following concepts
① Shared memory
There is a shared space that can be accessed directly between the communication processes , Here's the picture , in other words , Both processes on both sides of the communication can access this space

② The messaging
We are talking about message passing based on indirect communication （ mail ）, That is, the sending process sends the message to an intermediate entity , The receiving process then obtains information from the intermediate entity .

Pipeline communication

Understand the above two basic concepts , Let's talk about pipeline communication . In fact, the so-called pipeline communication is the combination of the above two principles , With Linux Take pipeline as an example

We know ,Linux Everything below is a document , therefore In essence, pipeline is also a kind of file , But it's different , It's like a fixed size buffer .
The process of pipeline communication is ： The writer process writes the message to the pipeline , The reading process is reading the message , Complete communication .

I said before. , Since the pipe is of fixed size , Then there is a time when it is full or empty , When the pipe becomes full , The write process will be blocked and can no longer write , When the pipe is empty , The read process cannot read any more ;
Also note ,① Reading data from the pipeline is a one-time operation , Once the data is read , Was abandoned by the pipeline , Release space .
② Pipes can only be used Half duplex communication , That is, only one-way transmission at a certain time , To realize the process interaction between the two sides , We need to define two pipelines .