Editing Redirection (computing) (section)

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{{Short description|Form of interprocess communication}}
{{distinguish|URL redirection}}
[[Image:Stdstreams-notitle.svg|thumb|300px|The standard streams for input, output, and error]]

In [[computing]], '''redirection''' is a form of [[interprocess communication]], and is a function common to most [[command-line interpreter]]s, including the various [[Unix shell]]s that can redirect [[standard streams]] to user-specified locations. The concept of redirection is quite old, dating back to the earliest operating systems (OS).{{cn|date=April 2024}} A discussion of the design goals for redirection can be found already in the 1971 description of the [[input-output]] subsystem of the [[Multics]] OS.{{sfn | Feiertag | Organick | 1972 | p=}} However, prior to the introduction of [[UNIX]] OS with its "[[Pipeline (Unix)|pipes]]", redirection in operating systems was hard or even impossible to do.{{sfn | Kernighan | Morgan | 1982 | p=780 | loc=Input/output redirection}}

In [[Unix-like]] operating systems, programs do redirection with the {{mono|[[dup2]](2)}} [[system call]], or its less-flexible but higher-level [[Standard streams|stdio]] analogues, {{mono|[[freopen]](3)}} and {{mono|[[popen]](3)}}.<ref>[https://www.gnu.org/software/libc/manual/html_mono/libc.html The GNU C Library Reference Manual for version 2.38] gnu.org</ref>