From 772f20abb0a3a0979c440114bf3a1cff5b3cef03 Mon Sep 17 00:00:00 2001 From: cvpcs Date: Wed, 2 Jun 2010 11:02:31 -0500 Subject: initial import of bash 4.1 --- doc/INTRO | 187 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 187 insertions(+) create mode 100644 doc/INTRO (limited to 'doc/INTRO') diff --git a/doc/INTRO b/doc/INTRO new file mode 100644 index 0000000..29f208a --- /dev/null +++ b/doc/INTRO @@ -0,0 +1,187 @@ + BASH - The Bourne-Again Shell + +Bash is the shell, or command language interpreter, that will appear +in the GNU operating system. Bash is an sh-compatible shell that +incorporates useful features from the Korn shell (ksh) and C shell +(csh). 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. + +Bash is quite portable. It uses a configuration system that discovers +characteristics of the compilation platform at build time, and may +therefore be built on nearly every version of UNIX. Ports to +UNIX-like systems such as QNX and Minix and to non-UNIX systems such +as OS/2, Windows 95, and Windows NT are available. + +Bash includes the following features: + +Editing and Completion + +Bash offers a command-line editing facility which permits users to +edit command lines using familiar emacs or vi-style editing commands. +Editing allows corrections to be made without having to erase back +to the point of error or start the command line anew. The editing +facilities include a feature that allows users to complete command and +file names. + +The Bash line editing library is fully customizable. Users may define +their own key bindings -- the action taken when a key is pressed. A +number of variables to fine-tune editing behavior are also available. + +History and Command Re-entry + +The Bash history feature remembers commands entered to the shell and +allows them to be recalled and re-executed. The history list may be +of unlimited size. Bash allows users to search for previous commands +and reuse portions of those commands when composing new ones. The +history list may be saved across shell sessions. + +Bash allows users to control which commands are saved on the history +list. + +Job Control + +On systems that support it, Bash provides an interface to the +operating system's job control facilities, which allow processes +to be suspended and restarted, and moved between the foreground +and background. Bash allows users to selectively `forget' about +background jobs. + +Shell Functions and Aliases + +These mechanisms are available to bind a user-selected identifier to a +list of commands that will be executed when the identifier is used as +a command name. Functions allow local variables and recursion, and +have access to the environment of the calling shell. Aliases may be +used to create a mnemonic for a command name, expand a single word to +a complex command, or ensure that a command is called with a basic set +of options. + +Arrays + +Bash-2.0 supports indexed arrays of unlimited size. The subscript for +an array is an arithmetic expression. Arrays may be assigned to with +a new compound assignment syntax, and several builtins have options to +operate on array variables. Bash includes a number of built-in array +variables. + +Arithmetic + +Bash allows users to perform integer arithmetic in any base from two +to sixty-four. Nearly all of the C language arithmetic operators are +available with the same syntax and precedence as in C. Arithmetic +expansion allows an arithmetic expression to be evaluated and the +result substituted into the command line. Shell variables can be used +as operands, and the value of an expression may be assigned to a +variable. + +An arithmetic expression may be used as a command; the exit status of +the command is the value of the expression. + +ANSI-C Quoting + +There is a new quoting syntax that allows backslash-escaped characters +in strings to be expanded according to the ANSI C standard. + +Tilde Expansion + +Users' home directories may be expanded using this feature. Words +beginning with a tilde may also be expanded to the current or previous +working directory. + +Brace Expansion + +Brace expansion is a convenient way to generate a list of strings that +share a common prefix or suffix. + +Substring Capabilities + +Bash allows new strings to be created by removing leading or trailing +substrings from existing variable values, or by specifying a starting +offset and length. Portions of variable values may be matched against +shell patterns and the matching portion removed or a new value +substituted. + +Indirect Variable Expansion + +Bash makes it easy to find the value of a shell variable whose name is +the value of another variable. + +Expanded I/O Capabilities + +Bash provides several input and output features not available in sh, +including the ability to: + + o specify a file or file descriptor for both input and output + o read from or write to asynchronous processes using named pipes + o read lines ending in backslash + o display a prompt on the terminal before a read + o format menus and interpret responses to them + o echo lines exactly as input without escape processing + +Control of Builtin Commands + +Bash implements several builtin commands to give users more control +over which commands are executed. The enable builtin allows other +builtin commands to be selectively enabled or disabled. The command +and builtin builtins change the order in which the shell searches for +commands. + +On systems that provide dynamic loading, new builtins may be loaded +into a running shell from a shared object file. These new builtins +have access to all of the shell facilities. + +Help + +Bash includes a built-in help facility. + +Shell Optional Behavior + +There is a great deal of customizable shell behavior. The shopt +builtin command provides a unified interface that allows users to +alter shell defaults. + +Prompt Customization + +Bash allows the primary and secondary prompts to be customized by +interpreting a number of backslash-escaped special characters. +Parameter and variable expansion is also performed on the values of +the primary and secondary prompt strings before they are displayed. + +Security + +Bash provides a restricted shell environment. It is also possible to +control the execution of setuid/setgid scripts. + +Directory Stack + +Bash provides a `directory stack', to which directories may be added +and removed. The current directory may be changed to any directory in +the stack. It is easy to toggle between two directories in the stack. +The directory stack may be saved and restored across different shell +invocations. + +POSIX Mode + +Bash is nearly completely conformant to POSIX.2. POSIX mode changes +those few areas where the Bash default behavior differs from the +standard to match the standard. In POSIX mode, Bash is POSIX.2 +compliant. + +Internationalization + +Bash provides a new quoting syntax that allows strings to be +translated according to the current locale. The locale in which the +shell itself runs may also be changed, so that the shell messages +themselves may be language-specific. + +The command-line editing facilities allow the input of eight-bit +characters, so most of the ISO-8859 family of character sets are +supported. + +Command Timing + +Bash allows external commands, shell builtin commands and shell functions +to be timed. The format used to display the timing information may be +changed by the user. -- cgit v1.1