Unix User Guide We Meet Again

UNIX Introduction

What is UNIX?

UNIX is an operating organisation which was first developed in the 1960s, and has been under constant evolution e'er since. By operating system, we hateful the suite of programs which make the figurer piece of work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.

UNIX systems also take a graphical user interface (GUI) similar to Microsoft Windows which provides an piece of cake to use environment. However, knowledge of UNIX is required for operations which aren't covered past a graphical program, or for when there is no windows interface available, for case, in a telnet session.

Types of UNIX

There are many different versions of UNIX, although they share mutual similarities. The most pop varieties of UNIX are Sunday Solaris, GNU/Linux, and MacOS Ten.

Here in the Schoolhouse, we employ Solaris on our servers and workstations, and Fedora Linux on the servers and desktop PCs.

The UNIX operating system

The UNIX operating organization is made up of three parts; the kernel, the vanquish and the programs.

The kernel

The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to system calls.

As an illustration of the way that the shell and the kernel work together, suppose a user types rm myfile (which has the event of removing the file myfile). The shell searches the filestore for the file containing the programme rm, and so requests the kernel, through system calls, to execute the program rm on myfile. When the procedure rm myfile has finished running, the shell and so returns the UNIX prompt % to the user, indicating that it is waiting for farther commands.

The shell

The shell acts as an interface betwixt the user and the kernel. When a user logs in, the login program checks the username and password, and and then starts another program chosen the crush. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arranges for them to exist carried out. The commands are themselves programs: when they terminate, the shell gives the user another prompt (% on our systems).

The proficient user can customise his/her ain shell, and users tin utilise different shells on the same machine. Staff and students in the school have the tcsh beat out by default.

The tcsh shell has certain features to help the user inputting commands.

Filename Completion - By typing part of the proper noun of a command, filename or directory and pressing the [Tab] key, the tcsh beat out volition complete the rest of the name automatically. If the shell finds more than than i name commencement with those messages you accept typed, it volition beep, prompting yous to blazon a few more messages before pressing the tab primal over again.

History - The vanquish keeps a list of the commands you have typed in. If you need to repeat a control, use the cursor keys to whorl upwardly and down the listing or type history for a list of previous commands.

Files and processes

Everything in UNIX is either a file or a process.

A process is an executing program identified by a unique PID (process identifier).

A file is a collection of data. They are created by users using text editors, running compilers etc.

Examples of files:

• a certificate (report, essay etc.)
• the text of a programme written in some high-level programming language
• instructions comprehensible direct to the machine and incomprehensible to a casual user, for instance, a collection of binary digits (an executable or binary file);
• a directory, containing information about its contents, which may exist a mixture of other directories (subdirectories) and ordinary files.

The Directory Structure

All the files are grouped together in the directory construction. The file-system is arranged in a hierarchical structure, similar an inverted tree. The top of the hierarchy is traditionally chosen root (written equally a slash / )

In the diagram above, we encounter that the dwelling house directory of the undergraduate student "ee51vn" contains two sub-directories (docs and pics) and a file called report.doctor.

The full path to the file report.doc is "/habitation/its/ug1/ee51vn/report.doc"

Starting an UNIX last

To open up an UNIX terminal window, click on the "Concluding" icon from Applications/Accessories menus.

An UNIX Terminal window will then appear with a % prompt, waiting for y'all to outset entering commands.

M.Stonebank@surrey.ac.great britain, © 9th October 2000

sullivanseessishe.blogspot.com

Source: http://www.ee.surrey.ac.uk/Teaching/Unix/unixintro.html

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