Shell script

This article is about scripting in Unix-like systems. For batch programming in DOS, OS/2 and Windows, see Batch file. For batch programming in Windows PowerShell shell, see Windows PowerShell § Scripting. For programming in the shells (cmd.exe) in operating systems of the Windows NT/2000 series, see cmd.exe. For shell programming, by means of files called Command Scripts or Procedures on Vax/VMS machines, see DIGITAL Command Language.
Editing a FreeBSD shell script for configuring ipfirewall

A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter.[1] The various dialects of shell scripts are considered to be command languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text. A script which sets up the environment, runs the program, and does any necessary cleanup or logging, is called a wrapper.

The term is also used more generally to mean the automated mode of running an operating system shell; each operating system uses a particular name for these functions including batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and mainframe operating systems are associated with a number of terms.

Shells commonly present in Unix and Unix-like systems include the Korn shell, the Bourne shell, and GNU Bash. While a Unix operating system may have a different default shell, such as Zsh on macOS, these shells are typically present for backwards compatibility.

  1. ^ Kernighan, Brian W.; Pike, Rob (1984), "3. Using the Shell", The UNIX Programming Environment, Prentice Hall, Inc., p. 94, ISBN 0-13-937699-2, The shell is actually a programming language: it has variables, loops, decision-making, and so on.