Terminal Commands Tutorial

As mentioned in the Terminal chapter, a command line interface (CLI) just uses text. This is quite different from how we usually use our computers and phones. This tutorial is meant to help you picture how your machine responds when you enter some common commands.

Note

For the purposes of this tutorial, we will use current_directory$ as the terminal prompt.

We will also use this file tree for the examples:

cd Command

cd directory_path moves us to the location described by directory_path.

Let’s start inside the LCHS directory.

Our current position is in the LCHS folder.

To move up one level into the parent directory, run the following commands in the terminal:

LCHS$ pwd
/MyLaptop/School/LCHS
LCHS$ cd ..
School$ pwd
/MyLaptop/School

Great! Now we’re inside the School folder.

Our current position is now in the School folder.

Note

The terminal does not display anything after a successful cd command. In the example above, we used the pwd command in lines 1 and 4 to check our location.

To make the actual move, only the cd command on line 3 is necessary.

To go back down into LCHS, we run cd ./LCHS:

School$ pwd
/MyLaptop/School
School$ cd ./LCHS
LCHS$ pwd
/MyLaptop/School/LCHS

OK, we’ve returned to where we started.

What if we want move to Chemistry from where we are now, in LCHS? Looking at the file tree again, we can trace the path we need to follow.

Path to move from LCHS into the Chemistry directory.

To make this move, first we need to go up one level into the parent directory, School. Next, we must move down into the Chemistry folder.

One way to do this is with two separate commands:

LCHS$ pwd
/MyLaptop/School/LCHS
LCHS$ cd ..
School$ cd ./Chemistry
Chemistry$ pwd
/MyLaptop/School/Chemistry

Line 3 moves us up one level into the School folder. Line 4 moves us from there down one level into Chemistry.

Tip

We can combine more than one navigation step into a single command. In the code above, we could replace lines 3 and 4 with cd ../Chemistry.

For more practice, let’s go from our current spot in Chemistry into the Homework folder. Looking back at the file tree, we need to move up one level (into School) and then down two levels into Homework.

Let’s start with a 3 step process:

Chemistry$ pwd
/MyLaptop/School/Chemistry
Chemistry$ cd ..
School$ cd LCHS
LCHS$ cd Homework
Homework$ pwd
/MyLaptop/School/LCHS/Homework

Notice that we used pwd again in lines 1 and 6 to check our location. We made the actual move in lines 3 - 5.

If we’re really confident, we can complete the move in a single command:

Chemistry$ pwd
/MyLaptop/School/Chemistry
Chemistry $ cd ../LCHS/Homework
Homework$ pwd
/MyLaptop/School/LCHS/Homework

Are you starting to see how terminal navigation can get you places quickly?

Let’s do one more quick move for fun. To go back to Chemistry, all we need to do is:

Homework$ pwd
/MyLaptop/School/LCHS/Homework
Homework$ cd ../../Chemistry
Chemistry$ pwd
/MyLaptop/School/Chemistry

cd ../../Chemistry tells the terminal, Move up one level, then move up another level, then move down into the Chemistry directory.

(Click here to return to the Terminal chapter).

clear Command

clear wipes the terminal window of all text. It gives us a clean screen whenever we need a fresh start.

clear doesn’t change our location in the file tree.

We usually don’t need to clear our terminal, but it’s a nice command to know for those who like to avoid clutter. As soon as we hit Enter after the command, the window looks as good as new!

LCHS$

(Return to the Terminal chapter).

cp Command

cp source_path target_path copies the item at the source and places a new version at the target path. The item can be a file or whole directory.

Our location is inside the Photos directory.

Let’s say we want to copy our cake.jpg file and place that copy inside the Desktop directory.

Photos$ ls
cake.jpg    puppy.jpg   bff.jpg
Photos$ cp /MyLaptop/Photos/cake.jpg /MyLaptop/Desktop
Photos$ ls
cake.jpg    puppy.jpg   bff.jpg
Photos$ ls ../Desktop
cake.jpg

1. Line 1 checks the contents of our current directory.

2. Line 3 makes a copy of the cake.jpg file (found at MyLaptop/Photos/cake.jpg) and places it into the /MyLaptop/Desktop location.

3. Lines 4 and 6 use the ls command to verify that cake.jpg now exists in two places on our device.

cake.jpg double take

We don’t actually need to be in the Photos directory to copy the cake.jpg file. We can run the cp command from any location. However, starting at the source_path helps us think through the process.

We can think of cp as basically copy and paste, since the target path is included in the command.

(Return to the Terminal chapter).

ls Command

Entering the ls command in the terminal returns the contents of the current directory.

For example, let’s assume we are in the Photos directory.

Our location is inside the Photos directory.

Now let’s display a list of the contents of the folder:

Photos$ ls
cake.jpg    puppy.jpg   bff.jpg

Line 1 is the command, and line 2 displays the returned message. All of that looks to be in order. Let’s move up one level into MyLaptop and run ls from there.

Photos$ pwd
/MyLaptop/Photos
Photos$ cd ..
MyLaptop $ pwd
/MyLaptop
MyLaptop $ ls
Desktop  Photos   School

Notice that ls only gives us a view one level deep. The command shows us that MyLaptop holds 3 other directories, but we do not see the contents of those folders.

(Return to the Terminal chapter).

man Command

man is a very good friend. Running man command gives you a summary of what that command does, what options it takes, and more documentation than we could ever need. It’s so thorough, it makes this short tutorial blush.

Anytime we have questions about how to use a command, we can access the manual to get more info!

Try It!

Look up some of the commands you know. Maybe you’ll learn a new option or two!

Some other terminal stuff we should know when using the manual:

1. Scrolling: Some entries are very long! You’ll know there’s more to read if you see : at the bottom of the terminal window. You can use your keyboard’s arrow keys to scroll through the text. Once you reach the bottom of the entry, you’ll see a line that reads END.

2. Exiting: Once you’re finished reading, exit the manual page by typing the letter q.

(Return to the Terminal chapter).

mkdir Command

mkdir folder_name creates a new directory inside your current location.

We will use the Photos directory for this example.

Our location is inside the Photos directory.

Let’s create a directory for pet photos:

Photos$ pwd
/MyLaptop/Photos
Photos$ ls
cake.jpg    puppy.jpg   bff.jpg
Photos$ mkdir fur_babies
Photos$ ls
cake.jpg    fur_babies  puppy.jpg   bff.jpg

Again, the computer does not return anything after the mkdir command on line 5. It just responds with another prompt. However, by using the helpful ls command, we see that a new directory was created.

Our file tree now looks like this:

mkdir creates a new directory.

Note

While mkdir creates a new directory, it does not move us into that location. Also, we don’t need to be in the parent of the newly created folder.

We can run mkdir from anywhere within the file system, as long as we use the correct file path.

(Return to the Terminal chapter).

mv Command

mv source_path target_path moves a file or directory from its old location in the file tree to a new one.

Our location is inside the Photos directory.

Let’s start in the Photos directory like we did with the cp command example. This time, instead of copying the cake.jpg file, we will move it into the Desktop folder.

Photos$ ls
cake.jpg    puppy.jpg   bff.jpg
Photos$ mv ./cake.jpg ../Desktop
Photos$ ls
puppy.jpg   bff.jpg
Photos$ cd ../Desktop
Desktop$ ls
cake.jpg    MiscDocs

Note the following:

1. In line 3, we used relative paths instead of absolute paths. ./cake.jpg means, Look in the current directory for the file called cake.jpg. The path ../Desktop means, Move up into the parent directory, then down into the Desktop folder.

2. On lines 1, 4, and 7, we use ls to verify our results.

Now our file tree looks like this:

mv moves cake.jpg from Photos into Desktop.

(Return to the Terminal chapter).

pwd Command

Entering the pwd command in the terminal returns our current location in the file tree. This is called our working directory.

LCHS $ pwd
/MyLaptop/School/LCHS

The working directory is another term for the current directory. Think of this command like the You Are Here dot on our file tree.

Our working directory is LCHS.

We are basically just asking the computer to give us our current location. This may seem basic, but the information is critical.

You need to know your current location when working in the terminal.

A lot of beginners enter commands into the terminal without paying attention to where they are. This often leads to mistakes and confusion. pwd is like a sanity check - a quick way to know where we are and what we are doing.

(Return to the Terminal chapter).

rm Command

rm file_name removes a given item from the file tree. This item can be a single file or an entire directory.

Removing a Single File

Let’s say we no longer want our cake.jpg photo. We can remove it!

Like many of the other terminal commands, we do NOT need to be in the same directory as the file we want to delete. For fun - and practice! - let’s remove cake.jpg while we’re located in the Homework directory.

Our current directory is Homework.

Homework$ pwd
/MyLaptop/School/LCHS/Homework
Homework$ rm /MyLaptop/Photos/cake.jpg
Homework$ cd /MyLaptop/Photos
Photos$ ls
puppy.jpg   bff.jpg

See what we did in line 3? Instead of moving into the parent directory of cake.jpg before removing it, we stayed in the Homework folder and used the full path to the file.

To check that our rm command did what we expected, we used the cd command in line 4. This moved us to the Photos directory. Then, a simple ls command returned the contents of that folder.

Here’s the map of what we’ve done:

cake.jpg is gone!

Removing a Directory

Warning

Removing a directory also deletes all of its contents.

To remove a directory, we need to include an option on the command. An option is an additional character, or set of characters, added on the end of a command. These characters give the computer more instructions about what you want it to do. Options are usually indicated with a -.

A common method to remove a directory is to use the -r option, although there are other choices. (Feel free to use the man rm command to read about these).

Let’s say we no longer want our Photos directory. Assume we are in the MyLaptop directory. Let’s see what happens when we try to use rm by itself:

MyLaptop$ ls
Desktop   Photos  School
MyLaptop$ rm Photos
rm: Photos: is a directory
MyLaptop $ ls
Desktop   Photos  School

Notice that simply using rm in line 3 returns a message telling us that Photos is a directory. The command does NOT delete the folder. This feature of rm helps prevent us from accidentally deleting a directory and all of its contents. Imagine what would happen if we entered rm /MyLaptop without this safety net!

Let’s try again, but this time we will add the -r option:

MyLaptop$ ls
Desktop   Photos  School
MyLaptop$ rm -r Photos
MyLaptop $ ls
Desktop   School

The rm command does not tell us when it successfully runs. The ls check on line 4 shows us that we’ve removed the Photos folder and everything inside of it.

Back in our map:

Photos is gone without a trace!

(Return to the Terminal chapter).

touch Command

touch new_filename creates a new file.

Our current directory is Homework.

In the Homework directory, lets add a new file called loop_practice.py.

Homework$ ls
hello.py   user_input.py
Homework$ touch loop_practice.py
Homework$ ls
hello.py   loop_practice.py   user_input.py

Here’s what the command on line 3 gives us:

touch adds a file.

(Return to the Terminal chapter).