Editing Pipeline (Unix) (section)

{{Short description|Mechanism for inter-process communication using message passing}}
{{About|the original implementation for shells|software pipelines in general|Pipeline (software)}}
[[File:Pipeline.svg|thumb|280px|A pipeline of three program processes run on a text terminal]]
In [[Unix-like]] computer [[operating system]]s, a '''pipeline''' is a mechanism for [[inter-process communication]] using message passing. A pipeline is a set of [[process (computing)|process]]es chained together by their [[standard streams]], so that the output text of each process (''[[stdout]]'') is passed directly as input (''[[stdin]]'') to the next one. The second process is started as the first process is still executing, and they are executed [[concurrency (computer science)|concurrently]].

The concept of pipelines was championed by [[Douglas McIlroy]] at [[Unix]]'s ancestral home of [[Bell Labs]], during the development of Unix, shaping its [[Unix philosophy|toolbox philosophy]]. It is named by analogy to a physical [[pipeline transport|pipeline]]. A key feature of these pipelines is their "hiding of internals". This in turn allows for more clarity and simplicity in the system.

The '''pipes''' in the pipeline are [[anonymous pipe]]s (as opposed to [[named pipe]]s), where data written by one process is buffered by the operating system until it is read by the next process, and this uni-directional channel disappears when the processes are completed. The standard [[Shell (computing)|shell]] syntax for [[anonymous pipe]]s is to list multiple commands, separated by vertical bars ("[[Pipe (character)|pipes]]" in common Unix verbiage).