View source for Software:Bash (Unix shell)

{{Short description|GNU replacement for the Bourne shell}}
{{Infobox software
| name = Bash
| logo = Gnu-bash-logo.svg
| screenshot = Bash screenshot.png
| caption = Screenshot of a Bash session
| author = Brian Fox
| developer = Chet Ramey<ref name="computerworld-Hamilton-Ramey">{{cite news |last1=Hamilton |first1=Naomi |title=The A-Z of Programming Languages: BASH/Bourne-Again Shell |website=Computerworld |url=http://www.computerworld.com.au/article/222764/ |archive-url=https://web.archive.org/web/20161108230747/http://www.computerworld.com.au/article/222764/ |archive-date=8 November 2016 |access-date=1 March 2022 |date=2008-05-30 <!-- https://web.archive.org/web/20081205093826/http://www.computerworld.com.au/index.php/id;1591223321;pp;2;fp;16;fpid;1 
 -->}}</ref><ref name="tiswww.case.edu-Ramey-BASH">{{cite web |last1=Ramey |first1=Chet |title=The GNU Bourne-Again Shell |url=https://tiswww.case.edu/php/chet/bash/bashtop.html |website=Technology Infrastructure Services |publisher=[[Organization:Case Western Reserve University|Case Western Reserve University]] |access-date=1 March 2022 |date=2021-04-20}}</ref>
| released = {{start date and age|1989|06|08}}
| latest release version = {{wikidata|property|preferred|references|edit|Q189248|P348|P548=Q2804309}}
| latest release date = {{wikidata|qualifier|preferred|single|Q189248|P348|P548=Q2804309|P577}}
| latest preview version = {{wikidata|property|preferred|references|edit|Q189248|P348|P548=Q51930650}}
| latest preview date = {{wikidata|qualifier|preferred|single|Q189248|P348|P548=Q51930650|P577}}
| programming language = [[C (programming language)|C]]
| operating system = {{Plainlist|
* [[Unix-like]]<ref>{{cite web|url=ftp://ftp.cwru.edu/pub/bash/FAQ|archive-url=https://web.archive.org/web/20180901171316/ftp://ftp.cwru.edu/pub/bash/FAQ|archive-date=September 1, 2018|url-status=dead|title=Bash FAQ, version 4.14|access-date=April 9, 2016|df=mdy-all}}</ref>
* [[Software:MacOS|macOS]] ([[Software:GNU General Public License#Version 2|GPL-2.0-or-later]]; GPL-3.0-or-later available through third parties)
* [[Software:Windows|Windows]] ([[Software:GNU General Public License#Version 3|GPL-3.0-or-later]])<ref>{{cite web|url=https://github.com/Microsoft/BashOnWindows/issues/107|title=Missing source code - GPL compliance? · Issue #107 · Microsoft/WSL|website=GitHub|access-date=July 8, 2016|archive-date=September 24, 2019|archive-url=https://web.archive.org/web/20190924163108/https://github.com/microsoft/WSL/issues/107|url-status=live}}</ref><ref>{{cite web|title=GNU Bash|url=http://www.softpedia.com/get/System/System-Miscellaneous/GNU-Bash.shtml|website=[[Softpedia]]|date=January 23, 2010|publisher=SoftNews|access-date=9 April 2016|archive-date=October 21, 2017|archive-url=https://web.archive.org/web/20171021004857/http://www.softpedia.com/get/System/System-Miscellaneous/GNU-Bash.shtml|url-status=live}}</ref>
* [[Software:BeOS|BeOS]],<ref name="forb">{{Cite web|url=https://www.forbes.com/1999/01/25/feat.html|title=A desktop alternative|website=Forbes}}</ref><ref>{{Cite web|url=http://testou.free.fr/www.beatjapan.org/mirror/www.be.com/documentation/user_docs/app_a_commandline.html|title=Appendix A: Using the BeOS Command Line Shell|website=testou.free.fr}}</ref> [[Software:Haiku (operating system)|Haiku]]<ref>{{cite web | url=https://www.haiku-os.org/docs/userguide/en/applications/terminal.html | title=Terminal }}</ref>
}}
| platform = [[Software:GNU|GNU]]
| language = Multilingual ([[Software:Gettext|gettext]])
| genre = [[Unix shell]], [[Command language|command language]]
}}

'''Bash''' is a [[Unix shell]] and [[Command language|command language]] written by Brian Fox for the [[GNU Project]] as a [[Free software|free software]] replacement for the [[Software:Bourne shell|Bourne shell]].<ref name="GNUBSD">{{Cite newsgroup
  | title = GNU + BSD = ?
  | author = [[Biography:Richard Stallman|Richard Stallman]] (forwarded with comments by Chet Ramey)
  | date = February 10, 1988
  | newsgroup = comp.unix.questions
  | message-id = 2362@mandrill.CWRU.Edu
  | url = https://groups.google.com/g/comp.unix.questions/c/iNjWwkyroR8/m/yedr9yDWSuQJ
  | access-date = December 28, 2021
  | quote = For a year and a half, the GNU shell was "just about done". The author made repeated promises to deliver what he had done, and never kept them. Finally I could no longer believe he would ever deliver anything. So Foundation staff member Brian Fox is now implementing an imitation of the Bourne shell.
  | archive-date = December 28, 2021
  | archive-url = https://web.archive.org/web/20211228023030/https://groups.google.com/g/comp.unix.questions/c/iNjWwkyroR8/m/yedr9yDWSuQJ
  | url-status = live
  }}</ref><ref>{{Citation |last=Hamilton |first=Naomi |title=The A-Z of Programming Languages: BASH/Bourne-Again Shell |date=May 30, 2008 |journal=Computerworld |page=2 |url=http://www.computerworld.com.au/article/222764/a-z_programming_languages_bash_bourne-again_shell/?pp=2&fp=16&fpid=1 |access-date=March 21, 2011 |archive-url=https://web.archive.org/web/20110706103704/http://www.computerworld.com.au/article/222764/a-z_programming_languages_bash_bourne-again_shell/?pp=2&fp=16&fpid=1 |archive-date=July 6, 2011 |url-status=dead |quote=When Richard Stallman decided to create a full replacement for the then-encumbered Unix systems, he knew that he would eventually have to have replacements for all of the common utilities, especially the standard shell, and those replacements would have to have acceptable licensing.}} Original computerworld.com.au link is dead: see also copies of original material at [https://a-z.readthedocs.io/en/latest/bash.html readthedocs.io], [https://www2.computerworld.com.au/article/222764/a-z_programming_languages_bash_bourne-again_shell/ computerworld.com.au] and [https://cse.sc.edu/~mgv/csce330f16/pres/az.pdf the University of South Carolina].</ref> The shell's name is an acronym for ''Bourne-Again SHell'', a [[Philosophy:Pun|pun]] on the name of the Bourne shell that it replaces<ref>{{Cite web|title=I Almost Get a Linux Editor and Compiler|url=http://www.drdobbs.com/i-almost-get-a-linux-editor-and-compiler/184404693|access-date=2020-09-12|website=Dr. Dobb's|archive-date=March 2, 2021|archive-url=https://web.archive.org/web/20210302212410/https://www.drdobbs.com/i-almost-get-a-linux-editor-and-compiler/184404693|url-status=live}}</ref> and the notion of being "[[Religion:Born again|born again]]".<ref>
{{cite web
  | author = [[Biography:Richard Stallman|Richard Stallman]]
  | title = About the GNU Project
  | publisher = [[Organization:Free Software Foundation|Free Software Foundation]]
  | date = November 12, 2010
  | url = https://www.gnu.org/gnu/thegnuproject.html
  | quote = "Bourne Again Shell" is a play on the name ''Bourne Shell'', which was the usual shell on Unix.
  | access-date = March 13, 2011
| archive-url= https://web.archive.org/web/20110424064815/https://www.gnu.org/gnu/thegnuproject.html| archive-date=April 24, 2011 | url-status= live}}
</ref><ref>
{{Citation
 |last        = Gattol
 |first       = Markus
 |title       = Bourne-again Shell
 |date        = March 13, 2011
 |url         = http://www.markus-gattol.name/ws/bash.html
 |quote       = The name is a pun on the name of the Bourne shell (sh), an early and important Unix shell written by Stephen Bourne and distributed with Version 7 Unix circa 1978, and the concept of being "born again".
 |access-date  = March 13, 2011
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20110309092607/http://www.markus-gattol.name/ws/bash.html
 |archive-date = March 9, 2011
 |df          = mdy-all
}}
</ref> First released in 1989,<ref name=BashBeta>{{Cite newsgroup
  | title = Bash is in beta release!
  | author = Brian Fox (forwarded by Leonard H. Tower Jr.)
  | date = June 8, 1989
  | newsgroup = gnu.announce
  | url = https://groups.google.com/group/gnu.announce/msg/a509f48ffb298c35?hl=en
  | access-date = October 28, 2010
  | archive-date = May 4, 2013
  | archive-url = https://web.archive.org/web/20130504075535/http://groups.google.com/group/gnu.announce/msg/a509f48ffb298c35?hl=en
  | url-status = live
  }}</ref> it has been used as the default [[Login|login]] shell for most [[Software:Linux|Linux]] distributions and it was one of the first programs Linus Torvalds ported to Linux, alongside [[Software:GNU Compiler Collection|GCC]].<ref name="groups.google.com">{{cite web|url = https://groups.google.com/group/comp.os.minix/msg/b813d52cbc5a044b|title = comp.os.minix|access-date = 2009-09-06|last = Torvalds|first = Linus Benedict|date=August 1991 | quote=I've currently ported bash(1.08) and gcc(1.40), and things seem to work.}}</ref> It is available on nearly all modern operating systems. 

Bash is a command processor that typically runs in a [[Terminal emulator|text window]] where the user types commands that cause actions. Bash can also read and execute commands from a file, called a [[Shell script|shell script]]. Like most Unix shells, it supports filename [[Glob (programming)|globbing]] (wildcard matching), [[Pipeline (Unix)|piping]], [[Here document|here document]]s, [[Command substitution|command substitution]], variables, and [[Control flow|control structures]] for condition-testing and [[Iteration|iteration]]. The [[Keyword (computer programming)|keywords]], [[Syntax (programming languages)|syntax]], [[Scope (computer science)#Dynamic scoping|dynamically scoped]] variables and other basic features of the language are all copied from [[Software:Bourne shell|sh]]. Other features, e.g., [[Software:C shell#History|history]], are copied from [[Software:C shell|csh]] and [[Software:KornShell|ksh]]. Bash is a [[POSIX]]-compliant shell, but with a number of extensions.

A version is also available for [[Software:Windows 10|Windows 10]] and [[Software:Windows 11|Windows 11]] via the [[Software:Windows Subsystem for Linux|Windows Subsystem for Linux]].<ref>{{cite web |date=September 28, 2016 |title=How to install Bash shell command-line tool on Windows 10 |url=http://www.windowscentral.com/how-install-bash-shell-command-line-windows-10 |url-status=live |archive-url=https://web.archive.org/web/20161120213017/http://www.windowscentral.com/how-install-bash-shell-command-line-windows-10 |archive-date=November 20, 2016 |access-date=November 20, 2016}}</ref><ref>{{Cite web |last=Hoffman |first=Chris |date=July 30, 2021 |title=How to Install the Windows Subsystem for Linux on Windows 11 |url=https://www.howtogeek.com/744328/how-to-install-the-windows-subsystem-for-linux-on-windows-11/ |access-date=2022-10-12 |website=How-To Geek |language=en-US}}</ref> It is also the default user shell in [[Software:Solaris (operating system)|Solaris]] 11.<ref>{{cite web |title=User Environment Feature Changes |url=https://docs.oracle.com/cd/E23824_01/html/E24456/userenv-1.html |url-status=live |archive-url=https://web.archive.org/web/20180612144748/https://docs.oracle.com/cd/E23824_01/html/E24456/userenv-1.html |archive-date=June 12, 2018 |access-date=June 8, 2018 |publisher=Oracle}}</ref> Bash was also the default shell in [[Software:BeOS|BeOS]],<ref name="forb" /> and in versions of [[Software:MacOS|Apple macOS]] from 10.3 (originally, the default shell was [[Software:Tcsh|tcsh]]) to 10.15 ([[Software:MacOS Catalina|macOS Catalina]]), which changed the default shell to zsh<ref name="zsh2" />, although Bash remains available as an alternative shell.<ref name=":0">{{Cite web |last=Hughes |first=Matthew |date=2019-06-04 |title=Why does macOS Catalina use Zsh instead of Bash? Licensing |url=https://thenextweb.com/dd/2019/06/04/why-does-macos-catalina-use-zsh-instead-of-bash-licensing/ |url-status=live |archive-url=https://web.archive.org/web/20201231231721/https://thenextweb.com/dd/2019/06/04/why-does-macos-catalina-use-zsh-instead-of-bash-licensing/ |archive-date=December 31, 2020 |access-date=2021-01-12 |website=The Next Web |language=en-us}}</ref>

A [[Security bug|security hole]] in Bash dating from version 1.03 (August 1989),<ref name="Seclists-20141004">{{cite web |last=Chazelas |first=Stephane |title=oss-sec mailing list archives |url=http://seclists.org/oss-sec/2014/q4/102 |date=4 October 2014 |work=Seclists.org |access-date=4 October 2014 |archive-date=October 6, 2014 |archive-url=https://web.archive.org/web/20141006093452/http://seclists.org/oss-sec/2014/q4/102 |url-status=live }}</ref> dubbed [[Software:Shellshock (software bug)|Shellshock]], was discovered in early September 2014 and quickly led to a range of attacks across the [[Internet]].<ref name="TR-20140924">{{cite web |last=Leyden |first=John |title=Patch Bash NOW: 'Shell Shock' bug blasts OS X, Linux systems wide open |url=https://www.theregister.co.uk/2014/09/24/bash_shell_vuln/ |work=The Register |date=September 24, 2014 |access-date=September 25, 2014 |archive-date=October 16, 2014 |archive-url=https://web.archive.org/web/20141016214010/http://www.theregister.co.uk/2014/09/24/bash_shell_vuln |url-status=live }}</ref><ref name="NYT-20140925-NP">{{cite news |last=Perlroth |first=Nicole |title=Security Experts Expect 'Shellshock' Software Bug in Bash to Be Significant |url=https://www.nytimes.com/2014/09/26/technology/security-experts-expect-shellshock-software-bug-to-be-significant.html |date=September 25, 2014 |work={{wipe|The New York Times}} |access-date=September 25, 2014 |archive-date=April 5, 2019 |archive-url=https://web.archive.org/web/20190405000511/https://www.nytimes.com/2014/09/26/technology/security-experts-expect-shellshock-software-bug-to-be-significant.html |url-status=live }}</ref><ref name="ZDN-20140929">{{cite web |last=Seltzer |first=Larry |title=Shellshock makes Heartbleed look insignificant |archive-url=https://web.archive.org/web/20160514191755/http://www.zdnet.com/article/hackers-jump-on-the-shellshock-bash-bandwagon/ |archive-date=May 14, 2016 |url=http://www.zdnet.com/shellshock-makes-heartbleed-look-insignificant-7000034143/ |date=29 September 2014 |work=[[ZDNet]]}}</ref> Patches to fix the bugs were made available soon after the bugs were identified.

==History== 
Brian Fox began [[Computer programming|coding]] Bash on January 10, 1988,<ref>{{Citation
  | author = Brian Fox
  | title = shell.c
  | publisher = [[Organization:Free Software Foundation|Free Software Foundation]]
  | date = August 29, 1996
  | url = http://ftp.gnu.org/gnu/bash/bash-1.14.7.tar.gz
  | quote = Birthdate: Sunday, January 10th, 1988. Initial author: Brian Fox
  | access-date = November 1, 2010
  | archive-date = September 28, 2018
  | archive-url = https://web.archive.org/web/20180928193215/http://ftp.gnu.org/gnu/bash/bash-1.14.7.tar.gz
  | url-status = live
  }}</ref> after [[Biography:Richard Stallman|Richard Stallman]] became dissatisfied with the lack of progress being made by a prior developer.<ref name=GNUBSD/> Stallman and the [[Organization:Free Software Foundation|Free Software Foundation]] (FSF) considered a free shell that could run existing shell scripts so strategic to a completely free system built from BSD and GNU code that this was one of the few projects they funded themselves, with Fox undertaking the work as an employee of FSF.<ref name=GNUBSD/><ref>
{{cite web
  | author = [[Biography:Richard Stallman|Richard Stallman]]
  | title = About the GNU Project
  | publisher = [[Organization:Free Software Foundation|Free Software Foundation]]
  | date = October 3, 2010
  | url = https://www.gnu.org/gnu/thegnuproject.html
  | access-date = March 21, 2011
  | quote = Free Software Foundation employees have written and maintained a number of GNU software packages. Two notable ones are the C library and the shell. … We funded development of these programs because the GNU Project was not just about tools or a development environment. Our goal was a complete operating system, and these programs were needed for that goal.
| archive-url= https://web.archive.org/web/20110424064815/https://www.gnu.org/gnu/thegnuproject.html| archive-date=April 24, 2011 | url-status= live}}
</ref> Fox released Bash as a beta, version .99, on June 8, 1989,<ref name=BashBeta/> and remained the primary maintainer until sometime between mid-1992<ref>{{Cite newsgroup
  | title = January 1993 GNU's Bulletin
  | author = len (g...@prep.ai.mit.edu)
  | date = April 20, 1993
  | newsgroup = gnu.announce
  | message-id = gnusenet930421bulletin@prep.ai.mit.edu
  | url = https://groups.google.com/group/gnu.misc.discuss/msg/4f42c739cd7e8bd8
  | access-date = October 28, 2010
  | archive-date = March 2, 2021
  | archive-url = https://web.archive.org/web/20210302213455/https://groups.google.com/forum/
  | url-status = live
  }}</ref> and mid-1994,<ref name="Bourne shell grammar">{{cite web|first=Chet|last=Ramey|title=Bash - the GNU shell (Reflections and Lessons Learned)|url=http://www.linuxjournal.com/article/2800#N0xa50890.0xb46380|access-date=November 13, 2008| date=August 1, 1994|work=Linux Journal| archive-url= https://web.archive.org/web/20081205082152/http://www.linuxjournal.com/article/2800| archive-date=December 5, 2008 | url-status= live}}</ref> when he was laid off from FSF<ref>{{Citation
  | title = Dates in your Computerworld interview
  | author = Chet Ramey
  | date = October 31, 2010
  | url = https://www.scribd.com/doc/40556434/2010-10-31-Chet-Ramey-Early-Bash-Dates
  | access-date = October 31, 2010
  | archive-date = July 20, 2012
  | archive-url = https://web.archive.org/web/20120720124341/http://www.scribd.com/doc/40556434/2010-10-31-Chet-Ramey-Early-Bash-Dates
  | url-status = live
  }}</ref> and his responsibility was transitioned to another early contributor, Chet Ramey.<ref>{{Cite newsgroup
  | title = Bash 0.99 fixes & improvements
  | author = Chet Ramey
  | date = June 12, 1989
  | newsgroup = gnu.bash.bug
  | url = https://groups.google.com/group/gnu.bash.bug/msg/1fc7b688f5d44438?hl=en
  | access-date = November 1, 2010
  | archive-date = November 10, 2012
  | archive-url = https://web.archive.org/web/20121110194014/http://groups.google.com/group/gnu.bash.bug/msg/1fc7b688f5d44438?hl=en
  | url-status = live
  }}</ref><ref>{{Cite newsgroup
  | title = Some bash-1.02 fixes
  | author = Chet Ramey
  | date = July 24, 1989
  | newsgroup = gnu.bash.bug
  | url = https://groups.google.com/group/gnu.bash.bug/msg/072a03645663caea?hl=en
  | access-date = October 30, 2010
  | archive-date = November 10, 2012
  | archive-url = https://web.archive.org/web/20121110194034/http://groups.google.com/group/gnu.bash.bug/msg/072a03645663caea?hl=en
  | url-status = live
  }}</ref><ref>{{Cite newsgroup
| title = Availability of bash 1.05
| author = Brian Fox
| date = March 2, 1990
| newsgroup = gnu.bash.bug
| url = https://groups.google.com/group/gnu.bash.bug/msg/e6112ccc8866e2f4?hl=en
| access-date = October 30, 2010
| archive-date = November 10, 2012
| archive-url = https://web.archive.org/web/20121110194052/http://groups.google.com/group/gnu.bash.bug/msg/e6112ccc8866e2f4?hl=en
| url-status = live
}}</ref>

Since then, Bash has become by far the most popular shell among users of Linux, becoming the default interactive shell on that operating system's various distributions<ref>{{cite book
| title = CompTIA Linux+ Powered by Linux Professional Institute Study Guide: Exam LX0-103 and Exam LX0-104
| edition = 3rd
| publisher = John Wiley & Sons, Inc.
| date = April 2015
| isbn = 978-1-119-02122-3
| last1 = Bresnahan
| first1 = Christine
| last2 = Blum
| first2 = Richard
| url = https://books.google.com/books?id=2P3zBgAAQBAJ&q=%22most+popular%22+linux+shell&pg=PA5
| quote = In Linux, most users run bash because it is the most popular shell.
| page = 5
| access-date = June 6, 2016
| archive-date = March 2, 2021
| archive-url = https://web.archive.org/web/20210302212409/https://books.google.com/books?id=2P3zBgAAQBAJ&q=%22most+popular%22+linux+shell&pg=PA5
| url-status = live
}}</ref><ref>{{cite book
| title = Mastering Linux
| publisher = John Wiley & Sons, Inc.
| date = February 2006
| isbn = 978-0-7821-5277-7
| last1 = Danesh
| first1 = Arman
| last2 = Jang
| first2 = Michael
| url = https://books.google.com/books?id=tIjrVYbZmUAC&q=bash+most+popular+unix+shell&pg=PA363
| quote = The Bourne Again Shell (bash) is the most common shell installed with Linux distributions.
| page = 363
| access-date = June 6, 2016
| archive-date = March 2, 2021
| archive-url = https://web.archive.org/web/20210302212410/https://books.google.com/books?id=tIjrVYbZmUAC&q=bash+most+popular+unix+shell&pg=PA363
| url-status = live
}}</ref> (although [[Software:Almquist shell|Almquist shell]] may be the default scripting shell) and on Apple's macOS releases before [[Software:MacOS Catalina|Catalina]] in October 2019.<ref>{{Cite book
| title = Beginning Shell Scripting
| publisher = John Wiley & Sons, Inc.
| date = April 2005
| isbn = 978-0-7645-9791-6
| last1 = Foster-Johnson
| first1 = Eric
| last2 = Welch
| first2 = John C.
| last3 = Anderson
| first3 = Micah
| url = https://books.google.com/books?id=dwIRERUpQPEC&q=bash+most+popular+unix+shell&pg=PA6
| quote = Bash is by far the most popular shell and forms the default shell on Linux and Mac OSX systems.
| page = 6
| access-date = June 6, 2016
| archive-date = March 2, 2021
| archive-url = https://web.archive.org/web/20210302212410/https://books.google.com/books?id=dwIRERUpQPEC&q=bash+most+popular+unix+shell&pg=PA6
| url-status = live
}}</ref><ref name="zsh1">{{cite web|url=https://support.apple.com/en-us/HT208050|title=Use zsh as the default shell on your Mac - Apple Support|access-date=1 July 2019|archive-date=December 2, 2019|archive-url=https://web.archive.org/web/20191202143802/https://support.apple.com/en-us/HT208050|url-status=live}}</ref><ref name="zsh2">{{Cite web|url=https://www.theverge.com/2019/6/4/18651872/apple-macos-catalina-zsh-bash-shell-replacement-features|title=Apple replaces bash with zsh as the default shell in macOS Catalina|last=Warren|first=Tom|date=June 4, 2019|website=The Verge|access-date=June 13, 2019|archive-date=June 10, 2019|archive-url=https://web.archive.org/web/20190610051842/https://www.theverge.com/2019/6/4/18651872/apple-macos-catalina-zsh-bash-shell-replacement-features|url-status=live}}</ref> Bash has also been ported to [[Software:Microsoft Windows|Microsoft Windows]] and distributed with [[Software:Cygwin|Cygwin]] and [[Software:MinGW|MinGW]], to [[Engineering:DOS|DOS]] by the [[Software:DJGPP|DJGPP]] project, to Novell NetWare, to [[Software:OpenVMS|OpenVMS]] by the GNV project,<ref>{{cite web|url=https://sourceforge.net/p/gnv/wiki/InstallingGNVPackages/|access-date=2020-09-04|title=Installing the new GNV packages|archive-date=October 3, 2020|archive-url=https://web.archive.org/web/20201003182204/https://sourceforge.net/p/gnv/wiki/InstallingGNVPackages/|url-status=live}}</ref> to [[Software:ArcaOS|ArcaOS]],<ref>{{cite web|url=https://www.arcanoae.com/wiki/arcaos/compatibility-subsystems/|title=Compatibility Subsystems|access-date=2020-09-04|archive-date=September 23, 2020|archive-url=https://web.archive.org/web/20200923001119/https://www.arcanoae.com/wiki/arcaos/compatibility-subsystems/|url-status=live}}</ref> and to [[Software:Android (operating system)|Android]] via various terminal emulation applications.

In September 2014, Stéphane Chazelas, a Unix/Linux specialist,<ref>{{cite news |last1=Juliana |first1=Cino |title=Linux bash exit status and how to set exit status in bash - Techolac |url=https://www.techolac.com/linux/linux-bash-exit-status-and-how-to-set-exit-status-in-bash/ |access-date=21 June 2019 |date=10 June 2017 |archive-date=June 21, 2019 |archive-url=https://web.archive.org/web/20190621183753/https://www.techolac.com/linux/linux-bash-exit-status-and-how-to-set-exit-status-in-bash/ |url-status=live }}</ref> discovered a [[Security bug|security bug]] in the program. The bug, first disclosed on September 24, was named [[Software:Shellshock (software bug)|Shellshock]] and assigned the numbers {{CVE|2014-6271|2014-6277|2014-7169|leadout=and}}. The bug was regarded as severe, since [[Common Gateway Interface|CGI]] scripts using Bash could be vulnerable, enabling [[Arbitrary code execution|arbitrary code execution]]. The bug was related to how Bash passes function definitions to subshells through [[Environment variable|environment variable]]s.<ref>{{Cite web
| author = Huzaifa Sidhpurwala
| title = Bash specially-crafted environment variables code injection attack
| publisher = [[Company:Red Hat|Red Hat]]
| url = https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/
| date = 2014-09-24
| access-date = September 25, 2014
| archive-date = September 25, 2014
| archive-url = https://web.archive.org/web/20140925035842/https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/
| url-status = live
}}</ref>

==Features==
The Bash [[Command (computing)|command]] syntax is a superset of the Bourne shell command syntax. Bash supports brace expansion,<ref>{{Cite web |title=Brace Expansion (Bash Reference Manual) |url=https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html |access-date=2024-01-10 |website=www.gnu.org}}</ref> command line completion (Programmable Completion),<ref>{{Cite web|url=https://www.gnu.org/software/bash/manual/bash.html#Programmable-Completion|title=Bash Reference Manual|website=www.gnu.org|access-date=March 27, 2018|archive-date=March 15, 2018|archive-url=https://web.archive.org/web/20180315115230/http://www.gnu.org/software/bash/manual/bash.html#Programmable-Completion|url-status=live}}</ref> basic debugging<ref>{{cite web|url=http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_02_03.html|title=Debugging Bash scripts|website=tldp.org|access-date=November 20, 2018|archive-date=November 4, 2018|archive-url=https://web.archive.org/web/20181104185300/http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_02_03.html|url-status=live}}</ref><ref>{{Cite web |title=The Set Builtin (Bash Reference Manual) |url=https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html |access-date=2024-01-10 |website=www.gnu.org}}</ref> and [[Signal (IPC)|signal handling]] (using <code>trap</code>) since bash 2.05a<ref>{{Cite web|url=https://wiki-dev.bash-hackers.org/scripting/bashchanges|title=Bash changes [Bash Hackers Wiki (DEV 20200708T2203)]|website=wiki-dev.bash-hackers.org|access-date=September 23, 2019|archive-date=September 23, 2019|archive-url=https://web.archive.org/web/20190923203509/https://wiki-dev.bash-hackers.org/scripting/bashchanges|url-status=live}}</ref><ref>{{Cite web |title=Bourne Shell Builtins (Bash Reference Manual) |url=https://www.gnu.org/software/bash/manual/html_node/Bourne-Shell-Builtins.html |access-date=2024-01-10 |website=www.gnu.org}}</ref> among other features. Bash can execute the vast majority of Bourne shell scripts without modification, with the exception of Bourne shell scripts stumbling into fringe syntax behavior interpreted differently in Bash or attempting to run a system command matching a newer Bash builtin, etc. Bash command syntax includes ideas drawn from the [[Software:KornShell|Korn Shell]] (ksh) and the [[Software:C shell|C shell]] (csh) such as command line editing, [[Command history|command history]] (<code>history</code> command),<ref>{{Cite web|url=https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Bash-History-Builtins|title=Bash Reference Manual|website=www.gnu.org|access-date=September 15, 2019|archive-date=September 15, 2019|archive-url=https://web.archive.org/web/20190915123105/http://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Bash-History-Builtins|url-status=live}}</ref> the directory stack, the <code>$RANDOM</code> and <code>$PPID</code> variables, and POSIX [[Command substitution|command substitution]] syntax <code>$(…)</code>.

When a user presses the tab key within an interactive command-shell, Bash automatically uses command line completion, since beta version 2.04,<ref>{{cite web|url=http://www.caliban.org/bash/index.shtml|title=Working more productively with bash 2.x/3.x|website=www.caliban.org|access-date=June 21, 2018|archive-date=June 29, 2018|archive-url=https://web.archive.org/web/20180629230903/http://www.caliban.org/bash/index.shtml|url-status=live}}</ref> to match partly typed program names, filenames and variable names. The Bash command-line completion system is very flexible and customizable, and is often packaged with functions that complete arguments and filenames for specific programs and tasks.

Bash's syntax has many extensions lacking in the Bourne shell. Bash can perform integer calculations ("arithmetic evaluation") without spawning external processes. It uses the <code>((…))</code> command and the <code>$((…))</code> variable syntax for this purpose. Its syntax simplifies [[Redirection (computing)|I/O redirection]]. For example, it can redirect standard output (stdout) and standard error (stderr) at the same time using the <code>&></code> operator. This is simpler to type than the Bourne shell equivalent '<code>command > file 2>&1</code>'. Bash supports [[Process substitution|process substitution]] using the <code><(command)</code> and <code>>(command)</code>syntax, which substitutes the output of (or input to) a command where a filename is normally used. (This is implemented through ''/proc/fd/'' unnamed pipes on systems that support that, or via temporary [[Named pipe|named pipe]]s where necessary).

When using the 'function' keyword, Bash function declarations are not compatible with Bourne/Korn/POSIX scripts (the KornShell has the same problem when using 'function'), but Bash accepts the same function declaration syntax as the Bourne and Korn shells, and is POSIX-conformant. Because of these and other differences, Bash shell scripts are rarely runnable under the Bourne or Korn shell interpreters unless deliberately written with that compatibility in mind, which is becoming less common as Linux becomes more widespread. But in POSIX mode, Bash conforms with POSIX more closely.<ref name="GNUBASHREF">
{{Citation
  | title = The GNU Bash Reference Manual, for Bash, Version 4.1
  | date = December 23, 2009
  | chapter = 6.11 Bash POSIX Mode
  | chapter-url = https://www.gnu.org/software/bash/manual/html_node/Bash-POSIX-Mode.html
  | access-date = October 26, 2010
  | url = https://www.gnu.org/software/bash/manual/html_node/index.html
| archive-url= https://web.archive.org/web/20101203065400/https://www.gnu.org/software/bash/manual/html_node/index.html| archive-date= December 3, 2010 | url-status= live}}
</ref>

Bash supports [[Here document|here document]]s. Since version 2.05b Bash can redirect standard input (stdin) from a "here string" using the <code><<<</code> operator.

Bash 3.0 supports in-process [[Regular expression|regular expression]] matching using a syntax reminiscent of [[Perl]].<ref>{{Cite web|url=http://www.tldp.org/LDP/abs/html/bashver3.html#BASH3REF|title=Advanced Bash-Scripting Guide|website=www.tldp.org|at=Section 37.2 (Bash, version 3)|access-date=2017-03-05|archive-date=May 5, 2017|archive-url=https://web.archive.org/web/20170505161903/http://tldp.org/LDP/abs/html/bashver3.html#BASH3REF|url-status=live}}</ref>

In February 2009,<ref>{{cite web|url=http://tldp.org/LDP/abs/html/bashver4.html|title=Bash, version 4|website=tldp.org|access-date=June 25, 2018|archive-date=July 1, 2018|archive-url=https://web.archive.org/web/20180701001653/http://www.tldp.org/LDP/abs/html/bashver4.html|url-status=live}}</ref> Bash 4.0 introduced support for associative arrays.<ref name="bashfaq061" />
Associative array indices are strings, in a manner similar to [[AWK]] or [[Tcl]].<ref>{{cite web|url=https://www.gnu.org/software/bash/manual/html_node/Arrays.html|title=Arrays (Bash Reference Manual)|website=www.gnu.org|access-date=July 4, 2018|archive-date=July 11, 2018|archive-url=https://web.archive.org/web/20180711142941/http://www.gnu.org/software/bash/manual/html_node/Arrays.html|url-status=live}}</ref> They can be used to emulate multidimensional arrays. Bash 4 also switches its license to [[Software:GNU General Public License#Version 3|GPL-3.0-or-later]]; some users suspect this licensing change is why MacOS continues to use older versions.<ref>{{cite web|url=https://apple.stackexchange.com/questions/193411/update-bash-to-version-4-0-on-osx|title=macos - Update bash to version 4.0 on OSX|website=Ask Different|access-date=June 25, 2018|archive-date=June 25, 2018|archive-url=https://web.archive.org/web/20180625213216/https://apple.stackexchange.com/questions/193411/update-bash-to-version-4-0-on-osx|url-status=live}}</ref> Apple finally stopped using Bash in its operating systems as default shell with the release of MacOS Catalina in 2019.<ref name=":0" />

===Brace expansion===
Brace expansion, also called alternation, is a feature copied from the [[Software:C shell|C shell]]. It generates a set of alternative combinations. Generated results need not exist as files. The results of each expanded string are not sorted and left to right order is preserved:

<source lang="console">
$ echo a{p,c,d,b}e
ape ace ade abe
$ echo {a,b,c}{d,e,f}
ad ae af bd be bf cd ce cf
</source>
Users should not use brace expansions in portable shell scripts, because the [[Software:Bourne shell|Bourne shell]] does not produce the same output.

<source lang="console">
$ # bash shell
$/bin/bash -c 'echo a{p,c,d,b}e'
ape ace ade abe
$ # A traditional shell does not produce the same output
$ /bin/sh -c 'echo a{p,c,d,b}e'
a{p,c,d,b}e
</source>

When brace expansion is combined with wildcards, the braces are expanded first, and then the resulting wildcards are substituted normally. Hence, a listing of JPEG and PNG images in the current directory could be obtained using:

<source lang="bash">
ls *.{jpg,jpeg,png}    # expands to *.jpg *.jpeg *.png - after which,
                       # the wildcards are processed
echo *.{png,jp{e,}g}   # echo just shows the expansions -
                       # and braces in braces are possible.
</source>

In addition to alternation, brace expansion can be used for sequential ranges between two integers or characters separated by double dots. Newer versions of Bash allow a third integer to specify the increment.

<source lang="console">
$ echo {1..10}
1 2 3 4 5 6 7 8 9 10
$ echo {01..10}
01 02 03 04 05 06 07 08 09 10
$ echo file{1..4}.txt
file1.txt file2.txt file3.txt file4.txt
$ echo {a..e}
a b c d e
$ echo {1..10..3}
1 4 7 10
$ echo {a..j..3}
a d g j
</source>

When brace expansion is combined with variable expansion (A.K.A. ''parameter expansion'' and ''parameter substitution'') the variable expansion is performed ''after'' the brace expansion, which in some cases may necessitate the use of the <code>eval</code> built-in, thus:

<source lang="console">
$ start=1; end=10
$ echo {$start..$end} # fails to expand due to the evaluation order
{1..10}
$ eval echo {$start..$end} # variable expansion occurs then resulting string is evaluated
1 2 3 4 5 6 7 8 9 10
</source>

===Startup scripts===

{{Section howto|date=January 2019}}

When Bash starts, it executes the commands in a variety of [[Hidden file and hidden directory#Unix and Unix-like environments|dot files]]. Unlike Bash shell scripts, dot files do typically have neither the execute permission enabled nor an [[Interpreter directive|interpreter directive]] like <code>#!/bin/bash</code>.

==== Legacy-compatible Bash startup example ====
The example <code>~/.bash_profile</code> below is compatible with the Bourne shell and gives semantics similar to csh for the <code>~/.bashrc</code> and <code>~/.bash_login</code>. The <code>[ -r ''filename'' ] && cmd</code> is a [[Short-circuit evaluation|short-circuit evaluation]] that tests if ''filename'' exists and is readable, skipping the part after the <code>&&</code> if it is not.

<source lang="bash">
[ -r ~/.profile ] && . ~/.profile             # set up environment, once, Bourne-sh syntax only
if [ -n "$PS1" ] ; then                       # are we interactive?
   [ -r ~/.bashrc     ] && . ~/.bashrc        # tty/prompt/function setup for interactive shells
   [ -r ~/.bash_login ] && . ~/.bash_login    # any at-login tasks for login shell only
fi                                            # End of "if" block
</source>

====Operating system issues in Bash startup====
Some versions of [[Software:Unix|Unix]] and [[Software:Linux|Linux]] contain Bash system startup scripts, generally under the <code>/etc</code> directory. Bash executes these files as part of its standard initialization, but other startup files can read them in a different order than the documented Bash startup sequence. The default content of the root user's files may also have issues, as well as the skeleton files the system provides to new user accounts upon setup. The startup scripts that launch the X window system may also do surprising things with the user's Bash startup scripts in an attempt to set up user-environment variables before launching the [[Window manager|window manager]]. These issues can often be addressed using a <code>~/.xsession</code> or <code>~/.xprofile</code> file to read the <code>~/.profile</code> — which provides the environment variables that Bash shell windows spawned from the window manager need, such as [[Software:Xterm|xterm]] or Gnome Terminal.

===Portability===
:See also: [https://www.gnu.org/software/bash/manual/bash.html#Major-Differences-From-The-Bourne-Shell Major Differences From The Bourne Shell]
Invoking Bash with the <code>--posix</code> option or stating <code>set -o posix</code> in a script causes Bash to conform very closely to the POSIX 1003.2 standard.<ref name=tldp>{{cite web|author=Mendel Cooper|title=Portability Issues|url=http://tldp.org/LDP/abs/html/portabilityissues.html|work=The Linux Documentation Project|publisher=ibiblio.org|access-date=January 26, 2012|archive-date=January 27, 2012|archive-url=https://web.archive.org/web/20120127105451/http://tldp.org/LDP/abs/html/portabilityissues.html|url-status=live}}</ref> Bash shell scripts intended for portability should take into account at least the POSIX shell standard. Some bash features not found in POSIX are:<ref name=tldp /><ref name=deb>{{cite web |title=10. Files |url=https://www.debian.org/doc/debian-policy/ch-files.html#scripts |website=Debian Policy Manual v4.5.0.2 |access-date=May 11, 2020 |archive-date=May 12, 2020 |archive-url=https://web.archive.org/web/20200512050159/https://www.debian.org/doc/debian-policy/ch-files.html#scripts |url-status=live }}</ref>

{{div col start}}
* Certain extended invocation options
* Brace expansion
* Arrays and associative arrays
* The double bracket {{code|...}} extended test construct and its regex matching
* The double-parentheses arithmetic-evaluation construct (only {{code|(( ... ))}}; {{code|$(( ... ))}} is POSIX)
* Certain string-manipulation operations in parameter expansion
* {{code|local}} for scoped variables
* Process substitution
* Bash-specific builtins
* [[Coprocess]]es
* $EPOCHSECONDS and $EPOCHREALTIME variables <ref>{{cite web|title=How To Format Date And Time In Linux, MacOS, And Bash?|url=https://www.shell-tips.com/linux/how-to-format-date-and-time-in-linux-macos-and-bash/#using-the-gnu-date-command-line|website=Shell Tips!|access-date=June 3, 2020|archive-date=June 3, 2020|archive-url=https://web.archive.org/web/20200603230615/https://www.shell-tips.com/linux/how-to-format-date-and-time-in-linux-macos-and-bash/#using-the-gnu-date-command-line|url-status=live}}</ref>
{{div col end}}

If a piece of code uses such a feature, it is called a "bashism" &ndash; a problem for portable use. Debian's {{code|checkbashisms}} and Vidar Holen's {{code|shellcheck}} can be used to make sure that a script does not contain these parts.<ref>{{man|1|checkbashisms|ManKier}}</ref><ref>{{man|1|shellcheck|ManKier}}</ref> The list varies depending on the actual target shell: Debian's policy allows some extensions in their scripts (as they are in the [[Software:Almquist shell#Dash|dash]] shell),<ref name=deb/> while a script intending to support pre-POSIX Bourne shells, like [[Software:Autoconf|autoconf]]'s {{code|configure}}, are even more limited in the features they can use.<ref>{{cite web |title=Portable Shell |url=https://www.gnu.org/software/autoconf/manual/html_node/Portable-Shell.html |website=Autoconf |access-date=20 January 2020 |archive-date=March 2, 2021 |archive-url=https://web.archive.org/web/20210302212413/https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.70/html_node/Portable-Shell.html |url-status=live }}</ref>

===Keyboard shortcuts===
{{Main article|Software:GNU Readline}}
Bash uses [[Software:GNU Readline|GNU Readline]] to provide keyboard shortcuts for command line editing using the default ([[Software:Emacs|Emacs]]) key bindings. Vi-bindings can be enabled by running <code>set -o vi</code>.<ref>{{cite web |url=http://www.hypexr.org/bash_tutorial.php#emacs |title=BASH Help - A Bash Tutorial |publisher=Hypexr.org |date=October 5, 2012 |access-date=July 21, 2013 |archive-date=March 2, 2021 |archive-url=https://web.archive.org/web/20210302213519/http://www.hypexr.org/bash_tutorial.php#emacs |url-status=live }}</ref>

===Process management (Job control)===
The Bash shell has two modes of execution for commands: batch (asynchronous), and concurrent (synchronous).

To execute commands in batch mode (i.e., in sequence) they must be separated by the character ";", or on separate lines:

<source lang="bash">
command1; command2
command3
</source>

In this example, when command1 is finished, command2 is executed, and when command2 has completed, command3 will execute.

A [[Background process|background execution]] of command1 can occur using (symbol &) at the end of an execution command, and process will be executed in background while returning immediately control to the shell and allowing continued execution of commands.
<source lang="bash">command1 &</source>

Or to have a concurrent execution of two command1 and command2, they must be executed in the Bash shell in the following way:

<source lang="bash">
command1 & command2
</source>

In this case command1 is executed in the background ''&'' symbol, returning immediately control to the shell that executes command2 in the foreground.

A process can be stopped and control returned to bash by typing {{Key press|Ctrl|z}} while the process is running in the foreground.<ref>{{cite web|url=https://www.gnu.org/software/bash/manual/bash.html#index-background|title=Bash Reference Manual|website=www.gnu.org|access-date=March 27, 2018|archive-date=March 15, 2018|archive-url=https://web.archive.org/web/20180315115230/http://www.gnu.org/software/bash/manual/bash.html#index-background|url-status=live}}</ref>

A list of all processes, both in the background and stopped, can be achieved by running <code>jobs</code>:
<source lang="console">
$ jobs
[1]-  Running                  command1 &
[2]+  Stopped                  command2
</source>

In the output, the number in brackets refers to the job id. The plus sign signifies the default process for <code>bg</code> and <code>fg</code>. The text "Running" and "Stopped" refer to the [[Process state|process state]]. The last string is the command that started the process.

The state of a process can be changed using various commands. The <code>fg</code> command brings a process to the foreground, while <code>bg</code> sets a stopped process running in the background. <code>bg</code> and <code>fg</code> can take a job id as their first argument, to specify the process to act on. Without one, they use the default process, identified by a plus sign in the output of <code>jobs</code>. The <code>[[Software:Kill (command)|kill]]</code> command can be used to end a process prematurely, by sending it a [[Signal (IPC)|signal]]. The job id must be specified after a percent sign:

<source lang="bash">
kill %1
</source>

===Conditional execution===
Bash supplies "conditional execution" command separators that make execution of a command contingent on the [[Exit status|exit code]] set by a precedent command. For example:

<source lang="bash">
cd "$SOMEWHERE" && ./do_something || echo "An error occurred" >&2
</source>

Where ''./do_something'' is only executed if the ''cd'' (change directory) command was "successful" (returned an exit status of zero) and the ''echo'' command would only be executed if either the ''cd'' or the ''./do_something'' command return an "error" (non-zero exit status).

For all commands the exit status is stored in the special variable <code>$?</code>. Bash also supports {{code|2=bash|if ...;then ...;else ...;fi}} and {{code|2=bash|case $VARIABLE in $pattern)...;;$other_pattern)...;; esac}} forms of conditional command evaluation.

===Bug reporting===
An external command called ''bashbug'' reports Bash shell bugs. When the command is invoked, it brings up the user's default editor with a form to fill in. The form is mailed to the Bash maintainers (or optionally to other email addresses).<ref>[http://linux.die.net/man/1/bashbug bashbug(1)] {{Webarchive|url=https://web.archive.org/web/20181002232146/https://linux.die.net/man/1/bashbug |date=October 2, 2018 }}, die.net</ref><ref>[https://developer.apple.com/library/prerelease/mac/documentation/Darwin/Reference/ManPages/man1/bashbug.1.html "Linux / Unix Command: bashbug"] {{Webarchive|url=https://web.archive.org/web/20141006131347/https://developer.apple.com/library/prerelease/mac/documentation/Darwin/Reference/ManPages/man1/bashbug.1.html |date=October 6, 2014 }}, apple.com</ref>

===Programmable completion===
Bash supports programmable [[Command-line completion|completion]] via built-in <code>complete</code>, {{Code|compopt}}, and <code>compgen</code> commands.<ref>{{Cite web|url=https://tiswww.case.edu/php/chet/bash/bashref.html#Programmable-Completion|title=Bash Reference Manual|website=tiswww.case.edu}}</ref> The feature has been available since the beta version of 2.04 released in 2000.<ref>{{Cite web|title=Working more productively with bash 2.x/3.x|url=http://www.caliban.org/bash/index.shtml|url-status=live|archive-url=https://web.archive.org/web/20180629230903/http://www.caliban.org/bash/index.shtml|archive-date=June 29, 2018|access-date=June 21, 2018|website=www.caliban.org}}</ref><ref>{{Cite web|url=https://ftp.swin.edu.au/gnu/bash/|title=Index of /gnu/bash|website=ftp.swin.edu.au|access-date=September 15, 2019|archive-date=March 8, 2020|archive-url=https://web.archive.org/web/20200308104032/http://ftp.swin.edu.au/gnu/bash/|url-status=live}}</ref> These commands enable complex and intelligent completion specification for commands (i.e. installed programs), functions, variables, and filenames.<ref name=":1">{{Cite web|title=An Introduction to Programmable Completion|url=https://tldp.org/LDP/abs/html/tabexpansion.html|access-date=2022-01-21|website=tldp.org}}</ref>

The <code>complete</code> and {{Code|compopt}} two commands specify how arguments of some available commands or options are going to be listed in the readline input. As of version 5.1 completion of the command or the option is usually activated by the {{Key|tab}} keystroke after typing its name.<ref name=":1"/>

=== Program name ===
The program's name is a figure of speech or [[Philosophy:Wit|witticism]] which begins with an [[Social:Homage (arts)|homage]] to [[Biography:Stephen R. Bourne|Stephen Bourne]], the creator of [[Software:Bourne shell|one]] of the shell programs which have sometimes been considered superseded by the bash shell. His name is used as a [[Philosophy:Pun|pun]] on the image of childbirth, and with that pun is added an allusion to the [[Religion:Christianity|Christian]] idiom of being "[[Religion:Born again|born again]]," or possibly the [[Religion:Buddhism|Buddhist]] idea of [[Philosophy:Reincarnation|reincarnation]]. Sometimes considered a reference to John 3 of the Christian [[Religion:New Testament|New Testament]], Merriam-Webster has "born-again" defined as "person who has made a renewed ... ''commitment'' of faith.<ref>{{Cite web |title=Definition of BORN-AGAIN |url=https://www.merriam-webster.com/dictionary/born-again |access-date=2024-01-09 |website=www.merriam-webster.com |language=en}}</ref>" This idiom is then used to name the program: the ''Bourne Again SHell''.<ref>{{Cite web |title=Bash - GNU Project - Free Software Foundation |url=https://www.gnu.org/savannah-checkouts/gnu/bash/bash.html |access-date=2024-01-10 |website=www.gnu.org}}</ref><ref>{{Cite web |title=What is Bash? (Bash Reference Manual) |url=https://www.gnu.org/software/bash/manual/html_node/What-is-Bash_003f.html |access-date=2024-01-09 |website=www.gnu.org}}</ref>     

The acronym of that name then is "bash," a word meaning "to strike violently.<ref>{{Cite web |date=2024-01-05 |title=Definition of BASH |url=https://www.merriam-webster.com/dictionary/bash |access-date=2024-01-09 |website=www.merriam-webster.com |language=en}}</ref>" In the context of computer programming, to "violently hit something," such as a computer keyboard, could be considered a hyperbolic image of some ''frustration''. Such imagery of negative emotionality could be seen as standing in direct juxtaposition to the idea of becoming "born again."    

The naming could be considered an instance of [https://literarydevices.net/irony/ verbal] irony or [https://literarydevices.net/innuendo accidental] [[Social:Innuendo|innuendo]]. Bash grammar was initially based on the grammars of the most popular Unix shell programs then currently in use, some of which were considered particularly difficult to use or ''frustrating'' at that time. As the years progressed, bash development has made its grammar more user-friendly,<ref>{{Cite web |title=BashGuide/Arrays - Greg's Wiki |url=https://mywiki.wooledge.org/BashGuide/Arrays |access-date=2024-01-10 |website=mywiki.wooledge.org}}</ref><ref>{{Cite web |title=CommandSubstitution - Greg's Wiki |url=https://mywiki.wooledge.org/CommandSubstitution |access-date=2024-01-10 |website=mywiki.wooledge.org}}</ref><ref>{{Cite web |title=BashGuide/TestsAndConditionals - Greg's Wiki |url=https://mywiki.wooledge.org/BashGuide/TestsAndConditionals#Conditional_Blocks_.28if.2C_test_and_.5B.5B.29 |access-date=2024-01-10 |website=mywiki.wooledge.org}}</ref><ref>{{Cite web |title=CHANGES - bash.git - bash |url=https://git.savannah.gnu.org/cgit/bash.git/tree/CHANGES |access-date=2024-01-10 |website=git.savannah.gnu.org}}</ref><ref>{{Cite web |date=2021-02-14 |title=Bash changes [Bash Hackers Wiki] |url=https://wiki.bash-hackers.org/scripting/bashchanges |access-date=2024-01-10 |archive-url=https://web.archive.org/web/20210214062716/https://wiki.bash-hackers.org/scripting/bashchanges |archive-date=February 14, 2021 }}</ref><ref>{{Cite web |date=2021-02-11 |title=Obsolete and deprecated syntax [Bash Hackers Wiki] |url=https://wiki.bash-hackers.org/scripting/obsolete |access-date=2024-01-10 |archive-url=https://web.archive.org/web/20210211050502/https://wiki.bash-hackers.org/scripting/obsolete |archive-date=February 11, 2021 }}</ref> so much so that it seems likely that the bash project has been ''committed'' to improving its usablilty. Since then, bash has become the de facto default shell program in most Linux and Unix operating systems.    

=== Documentation ===
The Linux [https://tiswww.case.edu/php/chet/bash/bash.html man] [https://git.savannah.gnu.org/cgit/bash.git/tree/doc/bash.0 page] is intended to be the controlling, authoritative source document for understanding how bash operates, while the GNU [https://www.gnu.org/software/bash/manual/index.html manual] is more user-friendly for reading. "You may also find information about Bash by running <kbd>info bash</kbd> ... or by looking at <code>/usr/share/doc/bash/</code>, <code>/usr/local/share/doc/bash/</code>, or similar directories on your system.  A brief summary is available by running <kbd>bash --help</kbd>.<ref>{{Cite web |title=Bash - GNU Project - Free Software Foundation |url=https://www.gnu.org/savannah-checkouts/gnu/bash/bash.html |access-date=2024-01-10 |website=www.gnu.org}}</ref>" "The maintainer also has a [https://tiswww.case.edu/php/chet/bash/bashtop.html Bash page] which includes [https://tiswww.case.edu/php/chet/bash/FAQ Frequently Asked Questions].<ref>{{Cite web |title=Bash - GNU Project - Free Software Foundation |url=https://www.gnu.org/savannah-checkouts/gnu/bash/bash.html |access-date=2024-01-10 |website=www.gnu.org}}</ref>"  As the standard upon which bash is based, [https://pubs.opengroup.org/onlinepubs/9699919799/ POSIX.1-2017] is also highly informative. Information on shell builtin commands can be found by executing <code>help</code>  or <code>help [builtin name]</code> at a terminal prompt where bash is installed. 

==Release history==
{| class="wikitable"
|-
! Version
! Release date
!Release notes
|-
| bash-5.2.15
| 2022-12-13
|[https://git.savannah.gnu.org/cgit/bash.git/tree/NEWS?h=bash-5.2 NEWS]
|-
| bash-5.2
| 2022-09-26
|
|-
| bash-5.1
| 2020-12-07
|[https://github.com/bminor/bash/blob/8868edaf2250e09c4e9a1c75ffe3274f28f38581/NEWS github version history NEWS] <ref name="bashfaq061" />
|-
| bash-5.0
| 2019-01-07
|<ref>{{Cite web|title=github version history NEWS v5.0|url=https://github.com/bminor/bash/blob/bash-5.0/NEWS|access-date=2021-03-01|website=GitHub|language=en|archive-date=May 4, 2022|archive-url=https://web.archive.org/web/20220504233136/https://github.com/bminor/bash/blob/bash-5.0/NEWS|url-status=live}}</ref><ref>{{Cite web |url=https://wiki.bash-hackers.org/scripting/bashchanges |title=Bash changes &#91;Bash Hackers Wiki&#93; |access-date=November 25, 2019 |archive-date=March 18, 2020 |archive-url=https://web.archive.org/web/20200318131209/https://wiki.bash-hackers.org/scripting/bashchanges |url-status=live }}</ref><ref>{{Cite web|title=Bash-5.0 release available|url=https://lists.gnu.org/archive/html/bug-bash/2019-01/msg00063.html|access-date=2021-03-01|website=lists.gnu.org|archive-date=November 8, 2020|archive-url=https://web.archive.org/web/20201108001733/https://lists.gnu.org/archive/html/bug-bash/2019-01/msg00063.html|url-status=live}}</ref>
|-
| bash-5.0-rc1
| 2018-12-20
|
|-
| bash-5.0-beta2
| 2018-11-28
|
|-
| bash-5.0-beta
| 2018-09-17
|
|-
| bash-5.0-alpha
| 2018-05-22
|
|-
| bash-4.4
| 2016-09-15
|[https://github.com/bminor/bash/blob/a0c0a00fc419b7bc08202a79134fcd5bc0427071/NEWS github version history NEWS v4.4]
|-
| bash-4.4-rc2
| 2016-08-22
|
|-
| bash-4.4-rc1
| 2016-02-24
|
|-
| bash-4.4-beta2
| 2016-07-11
|
|-
| bash-4.4-beta
| 2015-10-12
|
|-
| bash-4.3
| 2014-02-26
|
|-
| bash-4.2
| 2011-02-13
|
|-
| bash-4.1
| 2009-12-31
|
|-
| bash-4.0
| 2009-02-20
|
|-
| bash-4.0-rc1
| 2009-01-12
|
|-
| bash-3.2
| 2006-10-11
|
|-
| bash-3.1
| 2005-12-08
|
|-
| bash-3.0
| 2004-08-03
|
|-
| bash-2.05b
| 2002-07-17
|
|-
| bash-2.05a
| 2001-11-16
|
|-
| bash-2.05
| 2001-04-09
|
|-
| bash-2.04
| 2000-03-21
|
|-
| bash-2.03
| 1999-02-19
|
|-
| bash-2.02
| 1998-04-18
|
|-
| bash-2.01
| 1997-06-05
|
|-
| bash-2.0
| 1996-12-31
|
|}

==See also==
* [[Software:Comparison of command shells|Comparison of command shells]]
{{Clear}}

==References==
{{Reflist}}

==External links==
* {{cite news |last1=Hamilton |first1=Naomi |title=The A-Z of Programming Languages: BASH/Bourne-Again Shell |website=Computerworld |url=http://www.computerworld.com.au/article/222764/ |archive-url=https://web.archive.org/web/20161108230747/http://www.computerworld.com.au/article/222764/ |archive-date=8 November 2016 |date=2008-05-30 <!-- https://web.archive.org/web/20081205093826/http://www.computerworld.com.au/index.php/id;1591223321;pp;2;fp;16;fpid;1 
 -->}} (interview with GNU Bash's maintainer, Chet Ramey)

{{GNU}}
{{Unix shells}}{{Programming languages}}

{{DEFAULTSORT:Bash (Unix Shell)}}
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{{Sourceattribution|Bash (Unix shell)}}