SECTION 1 INTRODUCTION TO UNIX
1.0 1.1 1.2 1.3 1.4 1.5 Introduction Objectives Overview of Unix Unix Commands Summary Further Readings
Introduction to Unix
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This section is intended to introduce you to the Unix operating system. It will provide you with a basic understanding of the Unix operating system, its file and directory structure. We have also explained the architecture and components of Unix, further the section contains different useful Unix commands, and those are explained in detail with the help of examples.
After completing this lab manual, you should be able to: • • • • get basic understanding of the Unix operating system; understand file and directory structure of Unix; know the basic Unix commands; and know how to get Unix help.
1.2 OVERVIEW OF UNIX
Even after thirty-five years of its creation Unix is still regarded as one of the most versatile, flexible and powerful operating systems in the computer world. Before you start swimming in your Unix shell, you must find out why people still regard it as powerful. As you may know, it was created at Bell Labs in 1970, written in the C Programming Language, which was developed at the same time. It supports a large number of simultaneous users, runs with few alterations on many hardware platforms (provides some platform independence), and of course it was and is, a simple, elegant, and easy to use (at least compared to its predecessors) operating system. In the early 1980s, the two strands of Unix development – AT&T and Berkeley – continued in parallel. The Berkeley strand got a major boost from Sun Microsystems, which used the Berkeley code as the basis for its Sun OS operating system. This section is only a brief introduction to Unix operating system and does not include information on how to use all of its capabilities. Let’s see the historical development of Unix at a glance: • • • Kenneth Thompson, Dennis Ritchie, and others at AT&T Bell Labs developed first Unix version in 1969-1970. The above system was rewritten in the programming language C in 1972-1973. The seventh version (V7) of Unix was released in 1979. 5
During these 35 years of its development, different flavors of Unix system have evolved. Some of these Unix flavors are given on following Table 1 with the name of the organization which participated in that development. Table 1: List of Unix Flavors Unix flavor AIX FreeBSD HP-UX Irix Linux MacOS X Server NetBSD OpenBSD OpenLinux Red Hat Linux Reliant Unix SCO Unix Solaris SuSE Organization name IBM FreeBSD Group Hewlett-Packard Company Silicon Graphics, Inc. Several groups Apple Computer, Inc. NetBSD Group OpenBSD Group Caldera Systems, Inc. Red Hat Software, Inc. Siemens AG The Santa Cruz Operation Inc. Sun Microsystems S.u.S.E., Inc.
Due to, Unix is multi-user and multi-tasking environment, its flexibility and portability, facilities like electronic mail and the numerous programming, text processing and scientific utilities available, Unix became popular amongst the scientific and academic communities.
Basic Unix Elements
The six basic elements of Unix are: 1) 2) 3) 4) 5) 6) 1) 2) 3) 4) 5) 6 Commands Files Directories Environment Processes Jobs Commands are the instructions you give to the system to inform it what it is to do. Files are collections of data. A file is similar to a container in which you can store documents or raw facts and figures, which are stored in directories. Directory is similar to a file basket that contains many files. A directory can also contain other directories. Environment is a collection of different items that explain or modify how your computing session will be carried out. Process is a command or application running on a computer.
Job is the sequence of instructions given to a computer from the time to initiate a particular task. A job may have one or more processes in it.
Introduction to Unix...
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