Every operating system has a method of storing data in files and
directories so that it can keep track of additions, modifications,
and other changes. In Red Hat Enterprise Linux, every file is
stored in a directory. Directories can also contain directories:
these subdirectories may also contain
files and other subdirectories.
You might think of the file system as a tree and directories as
branches. There would be no tree without a root, and the same is
true for the Red Hat Enterprise Linux file system. No matter how
far away the directories branch, everything is connected to the
root directory, which is represented as a singe forward slash
(/).
3.2.1.
Paths
To continue the tree analogy from Section 3.2 A Larger Picture of the
File System, imagine navigating the file system as climbing
around in the branches of the tree. The branches you would climb
and traverse in order to get from one part of the tree to another
would be the path from one location to
another. There are two kinds of paths, depending on how you
describe them. A relative path describes
the route starting from your current location in the tree. An
absolute path describes the route to the
new location starting from the tree trunk (the root directory).
Graphic file browsers like Nautilus
use an absolute path to display your location in the file system.
At the top of a Nautilus browser window
is a location bar. This bar indicates your current location
starting with a forward slash (/) — this is an absolute path.
You can navigate the file system by entering the absolute path
here. Press [Enter] and Nautilus moves immediately to the new location
without navigating through the intervening directories one at a
time.
Navigating via the shell prompt utilizes either relative or
absolute paths. In some instances, relative paths are shorter to
type than absolute paths. In others, the unambiguous absolute path
is easier to remember.
There are two special characters used with relative paths. These
characters are "." and "..". A single period, ".", is shorthand for
"here". It references your current working directory. Two periods,
"..", indicates the directory one level up from your current
working directory. If your current working directory is your home
directory, /home/user/, ".." indicates
the next directory up, /home/.
Consider moving from the /usr/share/doc/ directory to the /tmp/ directory. The relative path between the two
requires a great deal of typing, and requires knowledge of the
absolute path to your current working directory. The relative path
would look like this: ../../../tmp/. The absolute path is much
shorter: /tmp/. The relative path
requires you to move up three directories to the / directory before moving to the /tmp/ directory. The absolute path, which always
starts at the / directory, is much
simpler.
However, the relative path between two closely-related
directories may be simpler than the absolute path. Consider moving
from /var/www/html/pics/vacation/ to
/var/www/html/pics/birthday/. The
relative path is: ../birthday/.
The absolute path is: /var/www/html/pics/birthday/. Clearly, the
relative path is shorter in this case.
There is no right or wrong choice: both relative and absolute
paths point to the same branch of the tree. Choosing between the
two is a matter of preference and convenience. Remember, the
Nautilus location bar does not recognize
the ".." symbol — you must use an absolute path.
