When a user presses the tab key within an interactive command-shell, Bash automatically uses command line completion, since beta version 2.04, to match partly typed program names, filenames and variable names. ![]() Bash command syntax includes ideas drawn from the KornShell (ksh) and the C shell (csh) such as command line editing, command history ( history command), the directory stack, the $RANDOM and $PPID variables, and POSIX command substitution syntax $(…). 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 supports brace expansion, command line completion (Programmable Completion), basic debugging and signal handling (using trap) since bash 2.05a among other features. ![]() The Bash command syntax is a superset of the Bourne shell command syntax. The bug was related to how Bash passes function definitions to subshells through environment variables. The bug was regarded as severe, since CGI scripts using Bash could be vulnerable, enabling arbitrary code execution. The bug, first disclosed on September 24, was named Shellshock and assigned the numbers CVE- 2014-6271, CVE- 2014-6277 and CVE- 2014-7169. In September 2014, Stéphane Chazelas, a Unix/Linux specialist, discovered a security bug in the program. Bash has also been ported to Microsoft Windows and distributed with Cygwin and MinGW, to DOS by the DJGPP project, to Novell NetWare, to OpenVMS by the GNV project, to ArcaOS, and to Android via various terminal emulation applications. 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 (although Almquist shell may be the default scripting shell) and on Apple's macOS releases before Catalina in October 2019. 99, on June 8, 1989, and remained the primary maintainer until sometime between mid-1992 and mid-1994, when he was laid off from FSF and his responsibility was transitioned to another early contributor, Chet Ramey. Stallman and the 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. Patches to fix the bugs were made available soon after the bugs were identified.īrian Fox began coding Bash on January 10, 1988, after Richard Stallman became dissatisfied with the lack of progress being made by a prior developer. Ī security hole in Bash dating from version 1.03 (August 1989), dubbed Shellshock, was discovered in early September 2014 and quickly led to a range of attacks across the Internet. The shell's name is an acronym for Bourne Again Shell, a pun on the name of the Bourne shell that it replaces and the notion of being " born again". Bash is a POSIX-compliant shell, but with a number of extensions. Other features, e.g., history, are copied from csh and ksh. The keywords, syntax, dynamically scoped variables and other basic features of the language are all copied from sh. Like most Unix shells, it supports filename globbing (wildcard matching), piping, here documents, command substitution, variables, and control structures for condition-testing and iteration. Bash can also read and execute commands from a file, called a shell script. īash is a command processor that typically runs in a text window where the user types commands that cause actions. Bash was also the default shell in versions of Apple macOS from 10.3 (originally, the default shell was tcsh) to 10.15 ( macOS Catalina), which changed the default shell to zsh, although Bash remains available as an alternative shell. It is also the default user shell in Solaris 11. ![]() A version is also available for Windows 10 and Windows 11 via the Windows Subsystem for Linux. Bash was one of the first programs Linus Torvalds ported to Linux, alongside GCC. First released in 1989, it has been used as the default login shell for most Linux distributions. macOS ( GPL-2.0-or-later GPL-3.0-or-later available through third parties)Ġ.99? to 1.05?: GPL-1.0-or-later īash is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell.
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