[Reading Notes] pipelines and FIFO

Source: Internet
Author: User

MPs queue

Provides a single (one-way) data stream, which can provide communication means between two different processes.

#include <unistd.h>     pipe( fd[]);

Returns two file descriptors, fd [0] () and fd [1] ().

Communication between pipelines is usually completed using the read and write Functions.


Typical pipeline usage:

First, the parent process creates an pipeline and then calls fork to derive a copy of itself.

Next, the parent process closes the read end of the pipeline, and the child process closes the write segment of the pipeline.

In this way, a one-way data flow is provided between parent and child processes.



When a two-way data flow is required, we must create two pipelines, one in each direction.

    pipe1[], pipe2[( (childpid = Fork()) ==);






It refers to the first in, first out, which is a one-way data stream.

Different from pipelines, each FIFO has a path name associated with it, which allows unrelated processes to access the same FIFO, and thus is also called "famous Pipeline ". ()

#include <sys/types.h><sys/stat.h> mkfifo( * pathname, mode_t mode);

Pathname is a path name and also the name of the FIFO.

Mode indicates the File Permission bit.



User (owner) read

User (owner) Write



(Owner) group member read

(Owner) group member write



Read by other members

Write by other members

The constant value oo_mode is defined in unpipc. h:



Unlike pipelines:


 FIFO1 "/tmp/fifo.1" FIFO2 "/tmp/fifo.2"( (mkfifo(FIFO1, FILE_MODE) < ) && (errno !=( (mkfifo(FIFO2, FILE_MODE) < ) && (errno !=( (childpid = Fork()) === Open(FIFO1, O_RDONLY, = Open(FIFO2, O_WRONLY,     = Open(FIFO1, O_WRONLY, = Open(FIFO2, O_RDONLY, );






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