computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...

, an anonymous pipe is a

simplex In geometry, a simplex (plural: simplexes or simplices) is a generalization of the notion of a triangle or tetrahedron to arbitrary dimensions. The simplex is so-named because it represents the simplest possible polytope in any given dimension. ...

FIFO communication channel that may be used for one-way

interprocess communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categori ...

(IPC). An implementation is often integrated into the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

's file IO subsystem. Typically a parent program opens anonymous pipes, and creates a new process that inherits the other ends of the pipes, or creates several new processes and arranges them in a

pipeline Pipeline may refer to: Electronics, computers and computing * Pipeline (computing), a chain of data-processing stages or a CPU optimization found on ** Instruction pipelining, a technique for implementing instruction-level parallelism within a s ...

Full-duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...

(two-way) communication normally requires two anonymous pipes. Pipelines are supported in most popular operating systems, from

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...

and

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

onwards, and are created using the ", " character in many shells.

Unix

Pipelines are an important part of many traditional

applications and support for them is well integrated into most

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating systems. Pipes are created using the pipe

system call In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...

, which creates a new pipe and returns a pair of

file descriptor In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typically have ...

s referring to the read and write ends of the pipe. Many traditional Unix programs are designed as

filters Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

to work with pipes.

Microsoft Windows

Like many other device IO and IPC facilities in the

Windows API The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations th ...

, anonymous pipes are created and configured with API functions that are specific to the IO facility. In this case CreatePipe is used to create an anonymous pipe with separate handles for the read and write ends of the pipe. Read and write IO operations on the pipe are performed with the standard IO facility API functions ReadFile and WriteFile. On

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

, reads and writes to anonymous pipes are always blocking. In other words, a read from an empty pipe will cause the calling thread to wait until at least one byte becomes available or an

end-of-file In computing, end-of-file (EOF) is a condition in a computer operating system where no more data can be read from a data source. The data source is usually called a file or stream. Details In the C standard library, the character reading functi ...

is received as a result of the write handle of the pipe being closed. Likewise, a write to a full pipe will cause the calling thread to wait until space becomes available to store the data being written. Reads may return with fewer than the number of bytes requested (also called a ''short read''). New processes can inherit handles to anonymous pipes in the creation process.

References

* Hart, Johnson M. ''Windows System Programming, Third Edition.'' Addison-Wesley, 2005. *

Notes

{{Inter-process communication Inter-process communication

Unix

Microsoft Windows

See also

References

Notes