You already should be familiar with two of the ls command’s more useful options:

1. -l, which displays the listing in long format
2. -F, which flags directory names with a trailing slash (/).

This lesson will introduce three more ls options: -a, -d, and -R.

Normally, the ls command does not display files that start with a dot (.).
These hidden files typically contain preference settings for certain UNIX commands.
If you want to list all files, including hidden files, use ls -a. Every directory contains at least two hidden files: the . and .. directories. They are shorthand for the current and parent directories respectively. When you specify a relative pathname using . or .., you are referencing these hidden directories.

Directories often contain other directories, which in turn can contain their own subdirectories, and so on down the file hierarchy. UNIX lets you display a directory tree all at once by using the ls -R command. The -R option produces a recursive listing .
That is, ls descends each subdirectory, listing the contents until the bottom of the hierarchy is reached.

Normally, when you specify a directory name with ls, you see the contents of the directory.
But if you want to display the directory itself, use the -d option.
The following Slide Show shows how to use the -a, -R, and -d options.