5.1 Filename

Unlike Windows and DOS, Linux filenames are case sensitive. In other words, error.txt and Error.txt are two distinct filenames. Keep this in mind, and use the convention of ``lowercase unless otherwise necessary'' to avoid problems with case sensitivity.

You can use practically any letter in a filename. However, I suggest that you limit to the letters, the dash (minus), the underscore and the dot (period). In Linux, you can even create filenames like a single space, two spaces, three spaces and etc. Obviously, such filenames are quite useless and can lead to lots of confusion.

The extension of a filename has no meaning to Linux and most programs that run in Linux. However, for your sake, use a common convention.

Any file that begins with a dot (period) is called a hidden file. This means that the command ls does not display files with names that begin with a dot, by default. You can use the -a option to make ls display ``hidden'' filenames.