Operating systems unix

A Short Introduction to UNIX Operating System

1. Operating Systems - Unix Presented by D.Achudhan. M.Sc Zoology Department of Animal H ealth And Management [email protected]

2. History of Linux Linux operating system developed by programming student Linus Torvalds Linus wanted to develop Unix-like OS just to experiment with new 386 computer at the time...

3. A Short Introduction to UNIX Operating System What Is UNIX? UNIX is an operating system which was first developed in the 1960s. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops. UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session.

4. UNIX Introduction The UNIX operating system is made up of three parts; the kernel, the shell and the programs. The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the file store and communications in response to system calls. The shell acts as an interface between the user and the kernel.

5. Types of UNIX There are many different versions of UNIX, although they share common similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X. The UNIX Operating System The UNIX operating system is made up of three parts; the kernel, the shell and the programs.

6. What is a programming language A programming language is an artificial language designed to express computations that will be executed on a computer. Programming languages have a syntax (form) and semantics (meaning). Java and C are example programming languages

7. 7 Unix Commands / home/larry # That “something” is called a prompt . As its name would suggest, it is prompting you to enter a command. Every unix command is a sequence of letters , numbers and characters . But there are no spaces. When you first log into a unix system, you are presented with something that looks like the following: Shell Commands of UNIX

8. 8 Unix is also case-sensitive . This means that cat and Cat are different commands. The prompt is displayed by a special program called the shell . Shells accept commands , and run those commands. They can also be programmed in their own language. These programs are called “ shell scripts ”.

9. 9 Unix provides files and directories . A directory is like a folder : it contains pieces of paper, or files. A large folder can even hold other folders- directories can be inside directories . In unix, the collection of directories and files is called the file system . Initially, the file system consists of one directory, called the “ root ” directory Inside “ root ” directory, there are more directories, and inside those directories are files and yet more directories. Stor i ng i nformat i on

10. 10 Each file and each directory has a name . A short name for a file could be joe , while it’s “ full name ” would be /home/larry/joe . The full name is usually called the path . The path can be divide into a sequence of directories. For example, here is how /home/larry/joe is read: /home/larry/joe The initial slash indicates the root directory . This signifies the directory called home . It is inside the root directory. The second slash corresponds to the directory larry , which is inside home. joe is inside larry .

11. 11 A path could refer to either a directory or a filename , so joe could be either. All the items before the short name must be directories. Root Directory Sub-Directory home Directory Directory larry joe File File Directory structure

12. Basic Commands ls list files and directories ls -a list all files and directories mkdir make a directory cd directory change to named directory cd change to home-directory cd ~ change to home-directory cd .. change to parent directory pwd display current dir path

13. Basic Commands cp file1 file2 copy file1 and call it file2 mv file1 file2 move or rename file1 to file2 rm file remove a file rmdir directory remove a directory cat file display a file more file display a file a page at a time who list users currently logged in lpr - Pprinter psfile print postscript file to named printer * match any number of characters ? match one character man command read the online manual page for a command

14. Basic Commands command > file redirect standard output to a file command >> file append standard output to a file command < file redirect standard input from a file grep 'keyword' file search a file for keywords % grep science science.txt wc file count number of lines/words/characters in file % wc -w science.txt sort sort data (numerically or alphabetically) Ex: to sort the list of object, type % sort < biglist and the sorted list will be output to the screen.

15. Illustration of Time-Sharing TIME User 1 User 2 User 3 User 4 User 5 User 6 User 7 User 8

16. UNIX Features The Unix OS is a multi-user OS allowing more that more person to directly communicate with the computer. Although the OS can only work on one task at a time, a small piece of time (time slice) is dedicated to each task or user - this is referred to as “time-sharing”. Time sharing gives the illusion that the CPU is giving all the users its full attention

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