shell: - Shell is a Unix term for the interactive user interface with an operating system. The shell is the layer of programming that understands and executes the commands a user enters. In some systems, the shell is called a command interpreter. A shell usually implies an interface with a command syntax (think of the DOS operating system and its "C:>" prompts and user commands such as "dir" and "edit"). As the outer layer of an operating system, a shell can be contrasted with the kernel, the operating system's inmost layer or core of services.

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ABOUT THE SHELLS

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The Startup Shell (startup.sh): The Startup Shell is a shell that is specific to Freenet. All TFN users have this shell as a default. (unless it is changed by TFN Admins) This shell allows users to access the menu driven features of Freenet. Currently, anyone logging into freenet who has this shell as a default will be disconnected.

The Bourne Shell (sh):The Bourne shell is the original Unix shell (command execution program, often called a command interpreter) that was developed at AT&T. Named for its developer, Stephen Bourne, the Bourne shell is also known by its program name, sh. The shell prompt (character displayed to indicate readiness for input) used is the $ symbol. The Bourne shell family includes the Bourne, Korn shell, bash, and zsh shells.

Bourne Again Shell (bash): is the free version of the Bourne shell distributed with Linux systems. Bash is similar to the original, but has added features such as command line editing. Its name is sometimes spelled as Bourne Again SHell, the capitalized Hell referring to the difficulty some people have with it.

Zsh (zsh): was developed by Paul Falstad as a replacement for both the Bourne and C shell. It incorporates features of all the other shells (such as file name completion and a history mechanism) as well as new capabilities. Zsh is considered similar to the Korn shell. Falstad intended to create in zsh a shell that would do whatever a programmer might reasonably hope it would do. Zsh is popular with advanced users.

Along with the Korn shell (ksh) and the C shell (csh):, the Bourne shell remains among the three most widely used and is included with all UNIX systems. The Bourne shell is often considered the best shell for developing scripts

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C shell (csh): is the Unix shell (command execution program, often called a command interpreter) created by Bill Joy at the University of California at Berkeley as an alternative to UNIX's original shell, the Bourne shell. These two UNIX shells, along with the Korn shell, are the three most commonly used shells. The C shell program name is csh, and the shell prompt (the character displayed to indicate readiness for user input) is the % symbol. The C shell was invented for programmers who prefer a syntax similar to that of the C programming language.

The other popular member of the C shell family is called tcsh (for Tab C shell) and is an extended version of C shell. Some of tcsh's added features are: enhanced history substitution (which allows you to reuse commands you have already typed), spelling correction, and word completion (which allows you to type the first couple of letters in a word and hit the tab key to have the p rogram complete it).

Once considered "buggy", the C shell has had a number of different versions developed to overcome the flaws in the original program. Most often, only experienced users prefer to use the C shell. C is frequently the default shell at universities and research organizations and is the default on many systems, especially those derived from Berkeley UNIX.