Unix, Part 3

One of the most useful concepts about Unix is its file system. Almost everything can be thought of as a file. Usually files are just things like programs or documents. Directories are files which describe a collection of files (and other directories). There are other important files associated with physical devices, such as hard disks, however you don't need to worry about them.

Directories can be placed within directories, resulting in a tree-like branched structure. There is one directory which is logically not in any other directory. This is called the "root" directory. Just to confuse people the root directory is usually drawn at the top of the tree. Of course, some people think that since it is called the root it must be at the bottom of the directory structure. These people are just being awkward and should be ignored. The root directory is signified by the character "/". So /tmp is the file or directory called tmp inside the root directory. (tmp is pronounce "temp" - short for temporary).

If you got a prompt, you are certainly running some kind of shell. "Shell" is a fancy name for the program which accepts commands that you type in, and then executes them on the unix system. There are many shells, including the bourne shell (sh), C shell (csh), korn shell (ksh) and T C shell (tcsh). It doesn't really matter which one you are using at the moment. You can try out the others later. For now you only need to type in letters and press delete or backspace to rub out characters typed in by mistake. (see later for the great Backspace/Delete Wars). Needless to say, you need to hit the Return key after each command. But don't hit it too hard.

Now, finally, we can try out some commands.

See also

• McLintock, Alexander Lachlan
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• Unix, Part 2
  /articles/1R22.html
• Unix, Part 1
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