16/September/2021 - Command Line Basics Part 2

Pre Requisites

Class Curriculum

Section content Expected time (mins) Pre - Requirements
Kahoot 15 minutes videos
Questions from Kahoot + Session 1 15 minutes ❌
Useful Terms/Concepts 5-10 minutes videos
Navigate file system and working with files & folders (demo) 10-15 minutes ❌
Quick overview of package managers 5-10 minutes ❌
Class break 10 minutes ❌
Command line practice in groups 40-50 minutes local terminal OR repl.it account
Summary & Next class overview 5 minutes ❌

Useful Terms/Concepts

  • File: data, usually organized according to some specific file format (e.g. txt, mp3, docx)
  • Directory: what we think of as a folder that contains files and other folders; in Linux systems, this is just a file that stores information about the length and location of other files, similar to a table of contents
  • File system: the part of an operating system that stores and keeps track of files
  • File permissions: define which users/groups are allowed to read/write/execute certain files. If a user has the following permissions, they can:
    • Read: view the contents of the file
    • Write: modify the contents of the file
    • Execute: run the program (remember: programs are also treated as "files" in Linux systems and are permissioned using the same terms!)

Navigate file system and working with files & folders (demo) | 10-15 minutes

Why use the command line?

  • once familiar with it, faster and easier to navigate the file system
  • offers many powerful tools (especially, but not limited to, text and file manipulation)
  • possible to group together commands and automate repeatable workflows
  • helpful (often required) when working on virtual machines or infrastructure in the cloud

Demo

Let's go through how to navigate the file system and work with files and folders. We will do this both via the command line using the commands listed in the cheat sheet below and then using the GUI (Graphical User Interface). Please refer to this cheat sheet when working through the exercises in groups later!

Command Line cheat sheet

Remember that you can look up what a command does by using the man (manual-pages) command on Mac and Linux, or help command on Windows cmd. For example: man echo would give you information on what the echo command does and how to use it.
command what it does
pwd print working directory (print the path to where I currently am in the file system)
cd change directory (this moves you, the viewer of the terminal, to a new location in the file system). You may use an absolute file path or a relative path where . is the current working directory and .. is the parent directory.
ls list the contents of the directory
mkdir make a directory
touch create a new file
rm delete a file (note: to delete a directory, add the option -r or -d)
cp copy a file (note: to copy a directory you probably need to add an option (like -r))
mv move a file or directory to a new location (note: this can also be useful for changing the name of a file/directory)
echo print some text; often used in conjunction with other commands
cat print the contents of the file
> this is an operator: X > Y will redirect (send) the outputs of command X to Y; if Y exists, it this will overwrite the existing file.
>> this is an operator similar to the above: X >> Y will send the outputs of command X to Y; if Y exists, it this will append to the existing file.

Quick overview of package managers

Packages are collections of files that are bundled together and can be installed and removed as a group

Package managers allow you to:

  • keep track of what software is installed
  • easily install new software
  • upgrade existing software to newer versions
  • remove or uninstall software.

There are different package managers available for different Operating Systems and Distributions. Here are some examples:

  • MacOS: homebrew, AppStore

  • Windows: PackageManagement, Chocalatey...

  • Linux: yum, apt-get, zypper

Tasks for group work

Work through the tasks with your partner/group. We recommend that one of you shares your screen and you discuss as a group how to proceed with each of the tasks. Each group member should be following along. It is totally fine if you don't complete all the tasks; make sure you understand how to do each task and ask questions if anything does not make sense! Complete any remaining tasks for homework.

0. Open a terminal window

Open a terminal window or Repl, where you can practice using the command line.

On Mac, you can do this by searching for "Terminal" in your Applications folder or using the keyboard shortcut "Command + Space" and then typing in "Terminal".

On Windows, open Cmder if you installed this as part of the prerequisites, or if you installed the Linux subsystem for windows, you can run WSL or follow the instructions described in the video. Alternatively, you can use Cygwin or the gitbash shell to practice Linux commands, or if nothing is available or working on your machine, please use Repl for today.

If you are running into any challenges with this, reach out to one of the teachers.

1. Move to the parent directory and back

  • Print your working directory
  • Move into the parent directory, if there is one.
  • Move back into the directory you came from.

Hint: if your original working directory path looked something like folder1/folder2/folder3, then for this task, you want to move to folder1/folder2 and then back to folder1/folder2/folder3.

2. Create a redi folder

Let's create a folder to store the work from this session.

  • Navigate to the place where you would like this folder to be located. The current working directory is fine, but you can also navigate to your desktop or another folder where you keep course work.
  • Create a new directory (folder) titled redi-2021-09-16
  • Move into this new directory and print your working directory. Double check that your working directory now includes redi-2021-09-16.

3. Create some files

Now let's create some files to go in this new directory.

  • Create an empty file called "test1.txt" using the touch command.

  • Create a second file called "hello.txt" which contains the phrase: "hello, my name is YOUR_NAME_HERE!". (Replace YOUR_NAME_HERE with your name :)) Hint: use the echo command and the > operator to do this.

  • List the files that are in the directory, and make sure that it looks something like:

    1test1.txt hello.txt

  • Append the line "How are you doing?" to the file "hello.txt"

  • Print the contents of the file and make sure that it looks something like:

    1hello! my name is YOUR_NAME_HERE!
2How are you doing?

4. Move these files into a new directory

Let's organize the directory that we are in by putting some of the files in a new location.

  • Create a folder (directory) called test-files in the redi-2021-09-16 folder
  • List the contents of the directory that you are in and make sure that it looks something like: 
    1test1.txt hello.txt test-files
  • Move test1.txt into the test-files directory.
  • List the contents of test-files and make sure it contains only test1.txt, and list the contents of redi-2021-09-16 to confirm that test1.txt has been moved.

5. Copy files and directories

  • Copy of hello.txt into the test-files directory. (Hint: this can be done in one command by copying the file to the proper location, or by creating a copy and then moving the file.)
  • Rename the original hello.txt to original-hello.txt. (Hint: "renaming" is the same as moving a file to a new file path.)
  • Make a copy of the test-files directory named test-files-copy.
  • List the contents of test-files-copy and make sure that it contains both test1.txt and original-hello.txt.

6. Delete files and directories

Be careful with this one! Please double check the command with one of the teachers before removing anything, since anything removed via rm cannot be retrieved!!

  • In the test-files-copy, delete the test1.txt file.
  • Confirm that test-files-copy contains only original-hello.txt.
  • Delete the entire test-files-copy directory.
  • List the contents of the redi-2021-09-16 directory and make sure that the test-files-copy directory is gone, but that the original test-files directory and other files are still present.

(Optional) 7. Additional Practice

These are additional challenge tasks that are meant to be extra challenging, in case the previous tasks went by more quickly than expected! :)

  • Use the man-pages and Google to understand how to use the grep command. Use this command to search for occurrences of the text "my name is" in the redi-2021-09-16 directory. (Hint: you can use the -r option to do this)
  • Create a journal/diary as a group with the following structure: the journal folder should contain year folders on the first level. Within a year folder are month folders, which contain text files for each individual day. A file path for one of these may look like: .../journal/2021/09/16.txt. Create a few entries that have some text!
  • Take a look at some of the extra resources :)

Extra resources

Next class preparation

Coming soon! Version Control with GIT