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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).
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.
Unix shells use dup2 for input/output redirection. Along with pipe(), it is a tool on which Unix pipes rely. The following example uses pipe() and dup() in order to connect two separate processes (program1 and program2) using Unix pipes:
The Linux tee command was written by Mike Parker, Richard Stallman, and David MacKenzie. [5] The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. [6] The FreeDOS version was developed by Jim Hall and is licensed under the GPL. [7]
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:
Another Unix breakthrough was to automatically associate input and output to terminal keyboard and terminal display, respectively, by default [citation needed] — the program (and programmer) did absolutely nothing to establish input and output for a typical input-process-output program (unless it chose a different paradigm).
Named pipes cannot be created as files within a normal filesystem, unlike in Unix. Also unlike their Unix counterparts, named pipes are volatile (removed after the last reference to them is closed). Every pipe is placed in the root directory of the named pipe filesystem (NPFS), mounted under the special path \\.\pipe\ (that is, a pipe named ...
Named pipe, an operating system construct intermediate to anonymous pipe and file. Pipeline (computing) for other computer-related versions of the concept. Kahn process networks to extend the pipeline concept to a more generic directed graph structure; Pipeline (Unix) for details specific to Unix; Plumber – "intelligent pipes" developed as ...