Top Ten Concepts for Linux Beginners – Number 2, Directories

linux57 Top Ten Concepts for Linux Beginners   Number 2, Directories
Levi Reiss asked:

Linux people like to claim that directories are really just another type of file. This statement can be misleading. We saw in a previous article that you create a file using a file editor. We will see later in this article how to create a directory.

So just what is a Linux directory? A directory is a collection that may include one or more directories, one or more files, or in fact be empty. You may think of a directory as a computerized file folder or loose-leaf notebook that contains dividers (themselves directories) and pages (files.) Just like a notebook page may not contain a divider, a Linux file may not contain a directory.

Up to now our comments about Linux directories hold for Windows directories as well. Now let’s take a look at some differences between these two systems. First come the naming conventions. Linux always distinguishes between lower-case and upper-case characters in directory names. Microsoft Windows does not. For example, Linux treats pay12june and Pay12june are as two different directories, as different as the directories pay12june and heighho. These directory names were used as file names in the previous article. While Linux does have some reserved directory and file names, in general one cannot tell by the name whether it is a file name or a directory name. So be careful. Linux helps you out here ‘ the ls command that lists the contents of a given directory usually displays files and directories in different colors.

Directories are hierarchical. They resemble a tree or a family tree. But unlike a tree (or Microsoft Windows) Linux has only one root. The root, designated as / lies at the top, rather than at the bottom, of the hierarchy. Right underneath the root directory you will find several subdirectories. For example, the /home directory is a child of / the root directory. The number and names of the first-level subdirectories vary from one version of Linux to another. For example, some Linux distributions include a /root directory while others do not. The /root directory (or subdirectory, both terms are used) is a child of /, the actual root directory.

The /home directory is an important directory. It is divided into subdirectories, one for each user. We like to work with Damn Small Linux, a free version of Linux that runs on the Windows desktop and requires only 50 Megabytes of disk space. Damn Small Linux automatically creates a user called dsl whose home directory is /home/dsl ; a working area essentially reserved for this user. All Linux versions subdivide the /home directory into user subdirectories according to this simple naming convention.

Linux provides several commands to process directories. For example, the mkdir command creates a directory. The rmdir command removes a directory, but in the simplest case only when it is empty. The cd command changes the working directory, the directory in which you are positioned. The pwd (print working directory) command displays (not prints) the working directory. Beginners should run this command often to reduce errors. For example, if you, the dsl user, think that you are positioned in the /home/dsl directory but in fact are positioned in the / directory you won’t be able save your files with a simple command. Why? Because you lack the requisite permission, the subject of our next article.

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