Chapter 1.1 - Hidden files, directory separators, the home directory

In this chapter, you will learn about how to hide a file or directory and what the home directory is.

Hiding files and directories

Let's look at the content of a directory I've just created:

nomike@max:/tmp/example$ ls -l
total 0
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:27 foo.txt

We have learned previously that we could create empty files with the touch command:

nomike@max:/tmp/example$ touch bar.txt

Let's look at the directory again:

nomike@max:/tmp/example$ ls -l
total 0
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:28 bar.txt
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:27 foo.txt

Let's create another file now and list our directory:

nomike@max:/tmp/example$ touch .rugby
nomike@max:/tmp/example$ ls -l
total 0
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:28 bar.txt
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:27 foo.txt

The file is not shown in our directory listing. We have just created a hidden file. Files are hidden, if their name starts with a ".".

Directories could be hidden as well:

nomike@max:/tmp/example$ mkdir .baz
nomike@max:/tmp/example$ ls -l
total 0
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:28 bar.txt
-rw-rw-r-- 1 nomike nomike 0 Dez 12 01:27 foo.txt

As they are only hidden, you could still interact with hidden files and directories:

nomike@max:/tmp/example$ cd .baz/
nomike@max:/tmp/example/.baz$ ls -l
total 0
nomike@max:/tmp/example/.baz$ cd ..

Showing hidden files and directories

The ls command has an option for showing hidden files called -A:

nomike@max:/tmp/example$ ls -l -A
total 4
-rw-rw-r-- 1 nomike nomike    0 Dez 12 01:28 bar.txt
drwxrwxr-x 2 nomike nomike 4096 Dez 12 01:34 .baz
-rw-rw-r-- 1 nomike nomike    0 Dez 12 01:27 foo.txt
-rw-rw-r-- 1 nomike nomike    0 Dez 12 01:30 .rugby

As you can see, our hidden file and hidden directory now show up.

There is another option which shows us a little more -a:

nomike@max:/tmp/example$ ls -l -a
total 24
drwxrwxr-x  3 nomike nomike  4096 Dez 12 01:34 .
drwxrwxrwt 36 root   root   16384 Dez 12 01:26 ..
-rw-rw-r--  1 nomike nomike     0 Dez 12 01:28 bar.txt
drwxrwxr-x  2 nomike nomike  4096 Dez 12 01:34 .baz
-rw-rw-r--  1 nomike nomike     0 Dez 12 01:27 foo.txt
-rw-rw-r--  1 nomike nomike     0 Dez 12 01:30 .rugby

In the previous chapter, you've learned that (almost) all directories contain the special items . and .. which refer to the current and to the parent directory. As both of these start with a ".", these are hidden by default as well, and the -a option needs to be used to show them.

Directory separators

In the examples of this course, you have seen directories nested into other directories. To separate directories and files from each other, the forward-slash character (/) is used.

For example foo/bar/baz.txt refers to a directory "foo" which contains a nested directory (also called a subdirectory) "bar" which contains the file "baz.txt".

Paths

If you specify directories and possibly a filename, separated by /s, which show you where you can find the item, this is called a "path".

Relative paths

A relative path, tells you, how to get to a certain location, from where you are right now. Relative paths must not start with a / character.

Simple paths could be:

Documents/tax-reports/2022.txt
document_root/index.html
Music

A path could also contain hidden items.

.state-secrets/roswell.txt
nomike/.hidden/desires.txt
../readme.txt
./foo.txt
../../
subfolder/././././././../foo.txt

As you can see, the special directories . and .. can be used in paths as well.

The root directory

As you have learned, unix organizes files within directories and you can traverse this hierarchy with the cd command. But where does this all start?

At the root directory.

The root directory could be found at the path /. All other files and directories are nested within the root directory.

Absolute paths

If a path starts with a / character, it is an absolute path, as it tells you how to find a certain item when you start looking from the root directory.

Some examples for absolute paths

/
/home/nomike/Documents/tax_form2021.txt
/usr/bin/ls
/usr/bin/mkdir
/usr/bin/rm
/etc/users

The home directory

Every user has a home directory. This is typically a directory named after the username and is located in /home. My home directory is thus /home/nomike.

When you login to a computer or open a terminal emulator, you're current working directory is typically set to your home directory.

As it usually is the directory you use the most, there are two short cuts here:

First of all, if you type cd without specifying a directory, it changes to your home directory:

nomike@max:/tmp/example$ cd
nomike@max:~$ pwd
/home/nomike
nomike@max:~$ 

And secondly, your home directory is abbreviated as ~. A cd ~ also sends you home and you can use it within paths as well. So if your username is nomike, the path /home/nomike/Pictures/portrait.txt is equal to ~/Pictures/portrait.txt.

In the exercise you can explore your filesystem.