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In computing, redirection is a form of interprocess communication, and is a function common to most command-line interpreters, including the various Unix shells that can redirect standard streams to user-specified locations. The concept of redirection is quite old, dating back to the earliest operating systems (OS).
Process substitution can also be used to capture output that would normally go to a file, and redirect it to the input of a process. The Bash syntax for writing to a process is >(command). Here is an example using the tee, wc and gzip commands that counts the lines in a file with wc -l and compresses it with gzip in one pass:
Rsh originated as part of the BSD Unix operating system, along with rcp, as part of the rlogin package on 4.2BSD in 1983. rsh has since been ported to other operating systems. The rsh command has the same name as another common UNIX utility, the restricted shell , which first appeared in PWB/UNIX ; in System V Release 4 , the restricted shell ...
Console redirection Stream redirection Configurability Startup/shutdown scripts Batch scripts Logging Available as statically linked, independent single file executable Thompson shell: UNIX: sh 1971 — UNIX: UNIX — Yes Text-based CLI: No No — Yes — — — — — — Bourne shell 1977 version 7th Ed. UNIX: sh 1977 Yes [1] 7th Ed. UNIX ...
For example, in a directory with three C source code files, rather than manually running the four commands required to build the final program from them, one could instead create a script for POSIX-compliant shells, here named build and kept in the directory with them, which would compile them automatically:
The Thompson shell was the first Unix shell, introduced in the first version of Unix in 1971, and was written by Ken Thompson. [1] It was a simple command interpreter, not designed for scripting, but nonetheless introduced several innovative features to the command-line interface and led to the development of the later Unix shells.
command is a shell command for Unix and Unix-like operating systems. It is used to execute a command whilst suppressing normal shell function lookup. [1] It is specified in the POSIX standard and is often implemented in Unix shells as a shell builtin function. Built-in functions take precedence over programs when resolving the name of a command.
An important aspect of this, setting Unix pipes apart from other pipe implementations, is the concept of buffering: for example a sending program may produce 5000 bytes per second, and a receiving program may only be able to accept 100 bytes per second, but no data is lost. Instead, the output of the sending program is held in the buffer.