Before we start our adventure to the depths of textual programs we have to open a terminal emulator as shown in the video below.

The commands you execute on the commandline always work relative to a directory on the filesystem. This directory is called the working directory and you can find out your current working directory by typing

pwd

on the commandline and hitting enter.

After hitting enter your terminal should show something like the following:

[user@computer ~]$ pwd
/home/user

This means that you are currently working in the /home/user directory.

Often times $ pwd (for “print working directory”) is used as an abbreviation to saying “Type pwd into a terminal emulator and hit the enter key”, the $ prefix stems from the way the terminal displays things, you should not type it in when asked to execute a program.

To demonstrate navigating the filesystem we first have to create some directories to navigate to. Execute the following commands to create the directories test_1 and test_2:

$ mkdir test_1
$ mkdir test_2

Now type $ ls (for “list”) to see the content of the current working directory. You should see, possibly among others, your newly created test folders.

[user@computer ~]$ ls
test_1
test_2

To change your current working directory you use the cd command:

[user@computer ~]$ pwd
/home/user
[user@computer ~]$ cd test_1
[user@computer ~/test_1]$ pwd
/home/user/test_1

To go up in the directory structure you can use .. in a path.

[user@computer ~/test_1]$ pwd
/home/user/test_1
[user@computer ~/test_1]$ cd ..
/home/user
[user@computer ~]$ cd test_2
[user@computer ~/test_2]$ pwd
/home/user/test_2
[user@computer ~/test_2]$ cd ../test_1
/home/user
[user@computer ~/test_1]$ pwd
/home/user/test_1

As typing is tedious you should, whenever possible, use the Tab ↹ key. When pressed once it will autocomplete whatever you entered as far as possible, when pressed twice it will show possible further completions. Try it by typing the following and pressing the tabulator key whenever a ↹ symbol comes up.

[user@computer ~/test_1]$ cd
[user@computer ~]$ cd te↹

(should autocomplete to test_)

[user@computer ~]$ cd test_↹↹
test_1/ test_2/

(should show options to go to)

To cancel the currently running program or to clear the current commandline you can use the key combination Ctrl+C (or Strg+C on a german keyboard). Pressing these two keys asks the running program to exit.

We will use a text editor to create a simple file. The text editor we use is called nano. To start it type the following:

[user@computer ~]$ cd
[user@computer ~]$ cd test_1
[user@computer ~/test_1]$ nano hello.txt

The last command starts an interactive text editor. For now just type hello world! and use the key combination Ctrl+X (Strg+X on a german keyboard) to exit the editor. The editor will ask if it should save the changes you made. Type Y (or J on a german system) and hit enter to save the changes and exit the editor.

To read the content of the file we just created we can either use nano to open it or the cat command to print its content to the terminal.

[user@computer ~/test_1]$ cat hello.txt
hello world!

Hint: Be careful when cating files to the terminal, sometimes when reading binary files instead of text files your terminal may end up all garbled up.

In addition to using the Tab ↹ key for autocompletions you should also use the command history. The terminal automatically keeps a log of the last commands you executed and you can navigate these commands using the arrow keys ↑↓ on your keyboard.

You can also search the history using the key combination Ctrl+R (Strg+R on a german keyboard).