Unix

UNIX 1. Give a small introduction to UNIX. UNIX is a family of multitasking, multi user operating systems that derive from the original AT & T Unix. Initially intended for use inside the Bell System. UNIX operating system provides simple tools which perform limited, well-defined functions such as base mechanisms for booting the computer, logging in, running applications, storing and retrieving files. UNIX is the first portable operating system and was written in C language which paved way in using UNIX in a variety of platforms. 2. What are the types of UNIX you know? Sun Solaris, GNU/Linux, Mac OS X 3. Name three parts of the UNIX operating system with a small description. 

The kernel The kernel of the UNIX is the heart of the operating system. It allocates memory and time to the programs and handles the file structure and communication between the different parts of the computer system such as the keyboard and the screen

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The shell The shell is an interface between the user and the UNIX kernel. It resembles ‘dos box’ that Windows displays if you run the command cmd. When a user logs in, UNIX checks their username and password and then starts a program called the shell. Shell interprets the commands the user types and transmits them to the kernel to be executed.

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The programs Programs are not part of the operating system as such, but they are logical sequences of commands, developed for implementing specific tasks. They usually include application software running at the user end.

4. Describe the importance of command shell. It is not possible to have a GUI equivalent of all the possible things you can do in a Command Line Interface. Some things are dramatically faster to do with a command line than with a GUI. This especially applies when you are working with servers or mainframes in an administrative capacity. A lot of administrative tasks

are many times faster with a command line interface (CLI) can save a huge amount of moving the mouse around and clicking. CLIs also require far less computer resources than GUIs, so they are favored on servers because you want to reserve most of the computer's horsepower for the services it provides to users. In UNIX based operating systems (like Linux or Mac OS X) the command line is incredibly useful. It enables users to have complete control of the operating systems, and do very complicated tasks in a few keystrokes. CLIs are also useful for operating computers remotely, because they use practically no bandwidth, whereas GUIs gobble bandwidth like there's no tomorrow. You can manage a dozen machines with as many CLI windows from one PC even on very slow connections, but trying to maintain a dozen GUI windows can easily choke a slow net connection. For example, with a single UNIX command, I can connect to an online database, search by name for the source code of an application, download that source code, find and download all of its required support files, compile the application into a binary file made specifically to run on my computer, and install the application. 5. What do following commands in UNIX do? Give an example. 

pwd (print working directory) Displays the full pathname of the current working directory in the standard output. Ex: $ pwd /home/workingdirectory

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cl Changes to lowercase all characters in a designated line of text. n - Specifies the number of lines of text to be changed to lowercase. Follow the n argument with a space.

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echo Outputting a string. Ex:

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date

$ echo "Text" Text

Displays/sets a system's date and time. Also a useful way to output/print current information when working in a script file. Ex:

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$ date Mon May 20 22:02:24 PDT 2013

ls Lists files and directories within the current working directory, and admins can determine when configuration files were last edited. Ex:

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$ ls Videos

Documents

Music

todo.txt

cd (change directory) Toggle between directories conveniently. Ex:

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C:\> cd games\New Folder C:\games\New Folder >

mv (move) The mv command moves a file to a different location or renames a file. Ex:

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mv one.txt two.txt mv three.txt ~/Desktop

rmdir (remove directory) Deleting a directory Ex:

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$ rmdir directoryname

rm (remove) Deleting a file Ex:

rm file

-renames the original file “one.txt” to “two.txt” -moves the file “three.txt” to your desktop directory but does not rename it. You must specify a new filename to rename a file.

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cat (concatenate) Displaying the content of a file. It can be used to read, modify or concatenate text files too. Ex:

$ cat filename