Directory operation

Filesystem structure

Every Linux file is contained in a collection called a directory. Directories are like folders on Windows and Mac systems. Directories form a hierarchy, or tree: one directory may contain other directories, called subdirectories, which may themselves contain other files and subdirectories, and so on, into infinity. The topmost directory is called the root directory and is denoted by a slash (/).

Path

We refer to files and directories using a “names and slashes” syntax called a path. To find out the current path, try

$ pwd

and you will get your current location in the filesystem.

There are two types of path. The first one is an absolute path. The absolute path starts from the root directory and has all the names of directories in the upper level. The second type is a relative path. The relative path does not start with the root directory or contain all the names of directories in the upper levels.

cd [directory]

To move your location in the shell environment, you can use the cd command:

$ cd /one/two/three

This command line moves you from your working directory (or current location) to /one/two/three. This example uses the absolute path to go to the new working directory. From here, you can use the relative path to go to /one/two with the following command:

$ cd ..

In the shell environment, ".." means the upper level. ("." means the current level.) You can use ".." as many times as you want. For example, if you want to move to /one from /one/two/three, you can type:

$ cd ../..

Please note that you can achieve the same result with the absolute path:

$ cd /one

Each user has own home directories where users’ personal files are often found. In general, the path of the home directory starts with /home. To find out the absolute path for your home directory, try:

$ echo $HOME

Linux offers a command that brings you to your home directory from anywhere. All you can do is just type cd with no arguments. It also provides a simple way to write the absolute path of your home directory with a special character, ~. Check this out.

$ echo ~

You will get the same result as above. This special character can be quite handy. Suppose you want to move to Documents/Public in your home directory from /one/two/three. Then you can just type:

$ cd ~/Documents/Public

If another username follows ~, the shell expands this string to be the user’s home directory:

$ cd ~smith
$ pwd
/home/smith

mkdir [options] directory

mkdir creates one or more directories:

$ mkdir dirname