Basic use of the command line

Learning to use the command line is essential for advanced programming, but it can also improve your day to day tasks. You can access your entire computer via the command line and do everything you can normally do using the Graphical User Interface... and more.

This (mini)tutorial will guide you through the very basics of using the command line.

When you launch a terminal, the default path/location is your home directory, however if at any point you are unsure which folder you are "in" (which is your working directory) you only need to type the command pwd.

Understanding the syntax

When you open the terminal you might see a prompt similar to:

username@computer ~ $

• The ~ character is typically shorthand for your home directory. Here you being told that your present working directory is your home directory.
• The $ (Ready) indicates that the prompt is ready to accept your command; the $ is just there, you do not need to type it.

Clear

At some point you might end up with your terminal full of lines. By typing the command clear you can clear the terminal screen.

Listing the Directory contents

If within a directory you want to see its content you can use the ls command.

If you need more detailed information on the contents (e.g. access permissions, date the file was last modified, etc.) you can use the command ls -l.

Moving between directories

To change your working directory you need to use the cd command (change directory), followed by the pathname of the directory you want to move into e.g:

cd /HelloWorld/src/

If you do not specify a pathname and just type cd, which will take you back to your home directory.

If you want to go to the previous directory (or a directory closer to the root) you can type cd ... This will take you back one directory at a time.

If you are trying to move to a directory that has spaces in the path you need to use "" to preserve the spaces: cd "Mini tutorial"

Creating directories

So far we have covered how to move between existing directories, but we can just as well create directories using the command line: mkdir HelloWorld If you want to create a folder within the HelloWorld directory you just created you can do it by typing mkdir HelloWorld/data without the need to change directories first.

If you need to create a multiple embedded directories, instead of creating one by one you can use the mkdir option -p which will create the parent directories i.e.

mkdir -p Helloworld/data/myproject/test1/

Creating files

You can create empty files using the touch command, for example touch project.scala. For this you need to be into the directory you want the file to be created, otherwise you need to specify the full path of the file:

touch HelloWorld/data/one.txt

You can even create multiple files at a time touch one.txt two.txt

Deleting files

To permanently delete files you can use the rm command e.g.

rm one.txt

Or even delete various files at a time

rm one.txt two.txt

To delete empty directories:

rmdir dir1/an-empty-dir

To recursively delete directories (delete non-empty directories and their contents):

rm -r dir1/dir_with_stuff_in

Copying files

You can copy files between directories by using cp source destination indicating the path of the file and then the path where you want the copy to be created.

But it is too much typing...

We've got you covered! Let's say you want to go to your data directory. You can start use the autocomplete function you can start typing cd HelloWorld/da and then press the Tab key on your keyboard and the prompt will... well autocomplete the path for you.