Assigment 3 (Linux Shell)

8/3/2019 Assigment 3 (Linux Shell)

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Assigment 3 (Linux Shell)

5.1.1 Shell Script

A shell script is a script written for the shell, or command line interpreter, of an operatingsystem. It is often considered a simple domain-specific programming language. Typical

operations performed by shell scripts include file manipulation, program execution, and printing

text.

5.1.2 Importance Of A Shell Script

A key feature of shell scripts is that the invocation of their interpreters are handled as a core

operating system feature. So rather than a user's shell only being able to execute scripts in thatshell's language, or a script only having its interpreter directive handled correctly if it was run

from a shell , shell scripts are set up and executed by the OS itself. A modern shell script is not

just on the same footing as system commands, but rather many system commands are actually

shell scripts.

5.1.3 Various Linux Shells

bash shell

Bash is an sh-compatible command language interpreter that executes commands read from

the standard input or from a file It is the shell for the GNU operating system from the GNU

Project. It can be run on most Unix-like operating systems. It is the default shell on most

systems built on top of the Linux kernel as well as on Mac OS X and Darwin.

C shell

The C shell is a command processor that's typically run in a text window, allowing the user to

type commands which cause actions. The C shell can also read commands from a file, called a

script. Like all Unix shells, it supports piping, here documents, command substitution, variables,control structures for condition-testing and looping and filename wildcarding.

Korn shell

The Korn shell is a command interpreter that allows an end user to type in commands to

communicate to the AIX system. By default, when a user logins, a shell process is started The

default AIX shell is /usr/bin/ksh.
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tcsh shell

Tcsh is C shell with file name completion, command line editing and other features such as

enhanced variable modifiers that make tcsh one of the most convenient shells for interactive

users. In tcsh environment variables are defined in upper and lowercase. Usually uppercase

parameters refer to parameters seen by all shells, while lowercase parameters are tcsh specific.

Ash shell

Ash is a fast, small, POSIX-compatible Unix shell designed to replace the Bourne shell in later

BSD distributions. Originally it did not feature line editing or command history mechanisms,

because Almquist felt that such should be moved into the terminal driver however, current

variants support it.

5.1.4 Shell Interface In Linux

Shell prompt

The shell is the program that waits for you to type in a Unix command and then press the return

key. Then the shell handles the execution of your command.

terminal window.

A terminal emulator, terminal application, term, or tty for short, is a program that emulates a

video terminal within some other display architecture. Though typically synonymous with a

command line shell or text terminal, the term terminalcovers all remote terminals, including

graphical interfaces. A terminal emulator inside a graphical user interface is often called a

terminal window.

Virtual Terminal

Virtual Terminal allows you to manually process credit card transactions from any computer with

an Internet connection in the world. You simply login to a secure website with a login and

password and you are able to charge cards, perform authorizations, and even process credits.

In addition, you have complete online reporting of all your transactions and orders.

In open systems, a virtual terminal (VT) is an application service that:

1. Allows host terminals on a multi-user network to interact with other hosts regardless ofterminal type and characteristics,

2. Allows remote log-on by local area network managers for the purpose of management,
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3. Allows users to access information from another host processor for transactionprocessing,

4. Serves as a backup facility.

5.2 Linux Text Editor

5.2.1 Various Text Editors:

Vi editor

Vi i is one of the most popular text editors texte under Unix type systems (with Emacsand pico).

Under Linux, there is a free version of Vicalled Vim(Vi Improved). Vi (pronounced vee-eye) is

an editor that is fully in text mode, which means that all actions are carried out with the help of

text commands. This editor, although it may appear of little practical use at first, is very powerful

and can be very helpful in case the graphical interface malfunctions.

Pico editor

The Pico text editor doesn't have a lot of fancy features, but it's a welcome alternative to the vi

or Emacs editors because learning it is quick and easy. Cursor movement and text entry are

straightforward, and--best of all--you don't have to learn any arcane commands: all commands

are listed in a handy menu at the bottom of the screen.

Joe editor

JOE is a blending of MicroPro's venerable microcomputer word processor WordStar andRichard Stallman's famous LISP based text editor GNU-EMACS, most of the basic editing keysare the same as in WordStar as is the overall feel of the editor. JOE also has some of the keybindings and many of the powerful features of EMACS

mcedit editor

Mcedit is a link to mc, the Midnight Commander, forcing it to immediately start its internal editor.

The editor is a terminal version of the cooledit standalone X Window editor.

Emacs editor

Emacs is a class of feature-rich text editors, usually characterized by their extensibility. Emacshas, perhaps, more editing commands than other editors, numbering over 1,000 commands. Italso allows the user to combine these commands into macros to automate work.
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Graphical Text Editor:

NEdit editor

NEdit is a multi-purpose text editor for the X Window System, which combines a standard, easyto use, graphical user interface with the thorough functionality and stability required by userswho edit text eight hours a day. It provides intensive support for development in a wide varietyof languages, text processors, and other tools, but at the same time can be used productively by

just about anyone who needs to edit text. NEdit, which is entirely a volunteer effort, benefitsfrom a strong developer and user community. As of version 5.1, NEdit may be freely distributedunder the terms of the GNU General Public License.

XEDIT editor

XEDIT is a visual editor for VM/CMS using block mode IBM 3270 terminals. It is much moreline-oriented than modern PC and Unix editors. For example, it supports automatic linenumbers, and many of the commands operate on blocks of lines. One of the features is a

command line which allows the user to type arbitrary editor commands. Because IBM 3270terminals do not transmit data to the computer until certain special keys are pressed (such asenter and function keys) XEDIT is less interactive than many PC and UNIX editors. Forexample, continuous spell-checking as the user types is impossible.
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Assigment 3 (Linux Shell)

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