The bash shell

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Bash is the shell, or command language interpreter, for the Linux operating system. The name is an acronym for the Bourne-Again SHell, a pun on Stephen Bourne, the author of the direct ancestor of the current Unix shell sh, which appeared in the Seventh Edition Bell Labs Research version of Unix Bash Reference Manual[1].

Introduction to the Bash Shell

A command line is a text user interface. One can use such an interface to provide instructions to a Linux powered computer. Under Linux, a programmed called shell used to provide a Linux command line user interface. The default shell for users in Linux is the GNU bash:

  • Developed by GNU project.
  • The default Linux shell on most Linux distributions.
  • Backward-compatible with the original sh UNIX shell.
  • Bash is largely compatible with sh and incorporates useful features from the Korn shell ksh and the C shell csh.
  • Bash is the default shell for Linux. However, it does run on every version of Unix and a few other operating systems such as ms-dos, os/2, and Windows platforms.

Quoting from the official Bash home page:

Bash is the shell, or command language interpreter, that will appear in the GNU operating system. It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2 Shell and Tools standard. It offers functional improvements over sh for both programming and interactive use. In addition, most sh scripts can be run by Bash without modification.

The command (shell) prompt

Typically you see a $ prompt when bash is waiting for a command from the user. This is called the command prompt or shell prompt. The default command prompt ends with a $ character for the regular user, and for the root user, the default prompt ends with a # character.

The default command (shell) prompt for a regular and root user

The improvements offered by BASH include:

The Bash syntax is an improved version of the Bourne shell syntax. In most cases Bourne shell scripts can be executed by Bash without any problems.

  • Command line editing.
  • Command line completion.
  • Unlimited size command history.
  • Prompt control.
  • Indexed arrays of unlimited size (Arrays).
  • Integer arithmetic in any base from two to sixty-four.
  • Bash startup files - You can run bash as an interactive login shell, or interactive non-login shell. See Bash startup files for more information.
  • Bash conditional expressions: Used in composing various expressions for the test builtin or [[ or [ commands.
  • The Directory Stack - History of visited directories.
  • The Restricted Shell: A more controlled mode of shell execution.
  • Bash POSIX Mode: Making Bash behave more closely to what the POSIX standard specifies.

Bash v4.0 Features


  • Brian J. Fox authored the GNU Bash shell, in 1987.
  • Fox maintained Bash as the primary maintainer until 1993, at which point Chet Ramey took over.
  • Chet Ramey is the current maintainer of the GNU Bourne Again Shell and GNU Readline.

Download Bash Shell

  • Bash is the default shell under Linux. The current production versions are Bash 3.x and 4.x. You can grab it from the official website.

External links


  1. Bash Reference Manual.

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