Inter-process communication-Named pipes

Concept

• One disadvantage of the pipeline is that there is no name, so it can only be used for inter-process communication with affinity, and the named pipe (named pipe or FIFO) solves this problem.

• FIFO provides a path name associated with it, stored in the file system as a FIFO file. The pathname in the file system is global and can be accessed by each process, so a path name in the file system can be used to identify an IPC channel.

• Anonymous pipelines (pipelines) are not visible to the file system, and are limited to communicating between the parent and child processes two processes. The named pipe is a visible file , so he can communicate between any two processes , regardless of whether the two processes are parent-child or not, regardless of whether the two processes are related to each other.
  

• FIFO always works according to the principle of FIFO (first Input first Output), the data that is written will first be read out of the pipeline.

• because everything in Linux can be considered a file, the use of named pipes becomes very , it is also very convenient to use, and we can use it as usual file name in the command.

To create a named pipe

There are two ways of creating named Pipes under Linux.

• Use the mkfifo command to interactively create a named pipe under the shell.

• Use the Mkfifo system call function in your program to create a named pipe.
  

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Pathname is the full pathname of the named pipe that was created, mode is the pattern that creates the named pipe, indicating its read and write permissions. Returns 0 on success, returns 1 on failure, and creates an appropriate error code.

Using Named pipes

Named pipes can be used after they are created, and the use of named pipes and pipelines is basically the same, except that when you use Named pipes, you must first open (). Because a named pipe is a file that exists on the hard disk, the pipeline is a special file that exists in memory.

It is important to note that a process that calls open () opens a named pipe may be blocked, ① but will not cause blocking if it is opened in both read and write mode (O_RDWR), and the process that calls the open () function will be blocked until a write party opens the pipeline if the ② is opened in read-only (o_rdonly) mode ③ if it is opened in write mode (o_wronly), it will also block until a read party opens the pipe.

Code

• FIFO Write End
  

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• FIFO Read End

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Inter-process communication-Named pipes