Slide 2.8: Seeking (cont.)
Slide 2.10: Unix shell built-in commands
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The Unix

All tools for this course could be found at the server shell, which uses the Linux operating systems. Linux is an implementation of Unix operating system.

Unix
Unix is an interactive time-sharing operating system invented in 1969 by Ken Thompson after Bell Labs left the Multics project. The turning point in Unix's history came when it was reimplemented almost entirely in C during 1972-1974, making it the first source-portable OS. Unix subsequently underwent mutations and expansions at the hands of many different people, resulting in a uniquely flexible and developer-friendly environment.

Directory Structure
Like other operating systems, Unix organizes user data, programs, etc. into structures called files. Files, in turn, are placed in directories. Directories are organized into a hierarchical structure, something like an upside down tree. This entire structure, including all of the directories and files, as well as the special structures the operating system uses to keep track of them, is called a file system.


The figure above shows a simplified Unix file system. At the top of the hierarchy is a special directory, called the root directory. This directory is represented by the ‘/’ character. Under the root directory, you will find a number of other directories (e.g., “bin” or “etc”). Under each of these, you might find more directories, and so on. Within these directories, you will find files containing all kinds of information.