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In computing, command substitution is a facility that allows a command to be run and its output to be pasted back on the command line as arguments to another command. . Command substitution first appeared in the Bourne shell, [1] introduced with Version 7 Unix in 1979, and has remained a characteristic of all later Uni
This provides the interfaces of piping, filters and redirection. Under Unix, devices are files too, so the normal type of file for the shell used for stdin, stdout and stderr is a tty device file. Another command-line interface allows a shell program to launch helper programs, either to launch documents or start a program.
PowerShell data sections can contain constants and expressions using a restricted subset of operators and commands. [79] PowerShell data sections are used when e.g. localized strings needs to be read from an external source while protecting against unwanted side effects.
PowerShell is a task automation and configuration management program from Microsoft, consisting of a command-line shell and the associated scripting language.Initially a Windows component only, known as Windows PowerShell, it was made open-source and cross-platform on August 18, 2016, with the introduction of PowerShell Core. [5]
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 introduction on Linux I/O Redirection "Linux I/O Redirection" Archived 10 June 2012 at the Wayback Machine with tee; GNU tee manual: duplicate standard input – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group; Plan 9 Programmer's Manual, Volume 1; Inferno General commands Manual
Python. The use of the triple-quotes to comment-out lines of source, does not actually form a comment. [19] The enclosed text becomes a string literal, which Python usually ignores (except when it is the first statement in the body of a module, class or function; see docstring). Elixir
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: