MA10126

Essential Unix

1. Introduction

What is Unix?

Unix is an operating system (OS) for computers. The operating system is the interface between the user and the central processor. Up to now, you have most likely only used the Windows® operating system on PCs (or the Mac OS on Apple machines). These are graphics-based operating systems: to give an instruction you use the mouse to click on an icon, or choose from a drop-down menu. Unix is a text-based OS: to issue a command you type a line of text and press the Return key. The system responds by typing text on the screen.

Back in the last century before the advent of Windows, PCs were controlled by a text-based operating system called MS-DOS. You can still see this on a PC: choose “command prompt” under Accessories, and you will see an MS-DOS window open, with a prompt “C:\>”. Try typing a command such as “dir” and press the Return key: the OS will respond with a list of your files and folders. Unix operates in just the same way.

Why do I have to learn Unix?

Good question! Let me try to explain the motivation. As mathematicians we clearly want to solve problems using maths, but unfortunately it is not always possible to succeed with the desired speed using our brainpower. Computers can help, for example some programs can do algebra (e.g. Mathematica), some can do integration (e.g. Matlab) etc. If a tailor-made program to solve a problem does not already exist, we can construct one ourselves using high-level programming languages such as Fortran, C++ or Java. If you are going to acquire these programming skills, then you want to be sure that you are the master giving the orders and the computer is your slave doing all the hard work! The way you communicate with your slave computer is via an operating system. Unix is the operating system used on the large computers at Bath and throughout much of the rest of the world. If you learn how to secure basic control of your computer with Unix, then the door is open to you to use existing – and to develop new – software tools to solve problems.

Why can’t I just use Windows?

Windows® is designed for PCs (or networks of PCs); Unix can be installed on any computer, and is the most common operating system for powerful ‘mainframe’ computers such as the Sun machines on the Bath network. You can talk to one of the Suns directly on a Unix terminal, or via a Unix window on a networked PC. You will need to do this when you want to run large, high-performance software.

Windows is an incredibly complex package, so it is a real pain for software developers to produce versions of their products which run under Windows. Because it is text-based, Unix is much simpler. Also, Windows is hedged round with copyrights and secrecy, while Unix is open-source – anyone can download the Unix OS and install it on their computer for free (or buy very cheaply the commercial version Linux). Consequently, licences for the Unix/Linux version of a software package are much cheaper than for the Windows® version, and a lot of software is only available for Unix.

Thirdly, although a text-based OS is simpler and appears much more primitive than one with flashy icons, Unix is actually much more powerful and versatile than Windows. You can do things (such as changing the access rights on files) which you can’t do in Windows.

Finally, Unix is not owned by a mega-corporation, is not plagued by bugs, does not get attacked by viruses, does not treat the user like an idiot, does not crash for no reason, …...

Okay, so teach me some Unix.

Read these pages by clicking on each link in turn, in the link bar at top or bottom of the page. The next page explains how to start a Unix session on a BUCS PC. Subsequent pages give you the basic commands for handling directories and files, editing textfiles, etc. Some of the pages have exercises for you to try; the solutions are provided (click on the hyperlinks). The final page has links to Unix online tutorials and the excellent Unix help pages from BUCS – these also recommend textbooks you can get.

Start now by clicking on “Logging in” in the linkbar below…