DEV Community: Maria Campbell

How to reuse an app created in one Django project in another Django project

Maria Campbell — Fri, 17 Jan 2025 13:03:43 +0000

Reusing an app created in one Django project in another Django project
- Copying an application from one Django project into another
Copying the polls app into a new top level directory called cast-votes
Configuring the polls app in cast-votes
Conclusion
Related Resources
Related Posts

Reusing an app created in one Django project in another Django project

I have created enough Django apps at this point that can be
reusable in other Django projects other than the ones they were
initially created in. It is smart and efficient development to be
able to do so. Why re-create something which already exists
somewhere else? This is a great path to creating reusable apps that
others can also use in their Django projects. It also paves a path
to writing great documentation for these apps.

Copying an application from one Django project into another

Following the
"Writing your first Django app"
series, I created a project called django_polls inside a top level
directory called django-polls. This was all fine. The app was
standalone, and that was great. But the problems began when I found
out about the Django advanced tutorial called
"Advanced tutorial: How to write reusable apps".
I approached the django_polls project like I would any other with the
naming. I did not know what was coming up next, and neither was
I appraised of it beforehand.

In this post, I will discuss how to avoid as muchas possible
such naming conflicts whilestill naming projects and reusable apps
with professional sounding names.

Copying the polls app into a new top level directory called cast-votes

I arbitrarily named anew top level directory cast-votes, and inside
I created a new project called config. I came across a number of
posts and threads where Django developers repeatedly called their
projects "config" so that there would be less of a chance of
naming conflicts when installing reusable apps. I thought it a
great idea, and decided to do the same for the purpose of this post.
It looks like I might continue to follow this convention!

You can follow the steps to creating a new project in my post
entitled
Creating the official Django Polls app Part 1.
However, this time, instead of creating a top level directory called
django-polls, and then a project called django_polls, create a top
level directory called cast-vote and a project called config inside
cast-vote.

If you have already completed the
Creating the official Django Polls app
series and therefore created an app called polls, you can copy the
polls app directory into the root of the cast-votes directory. There
should be no conflicts, since the project name does not contain
"polls" in it. It's as generic as it can get. We are not thinking
about creating a package from polls yet. That will take place in
another post. Right now we just want to make sure that our polls app
can be reused by ourselves on our local machine.

Configuring the polls app in cast-votes

Once we have placed polls inside the top level cast-votes directory,
we need to configure it a bit. The steps are not dissimilar from those
we were supposed to take to prepare our polls app package in the
"Advanced tutorial: How to write reusable apps".

First, we have to add polls to INSTALLED_APPS in config/settings.py:

INSTALLED_APPS = [
    "django.contrib.admin",
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.messages",
    "django.contrib.staticfiles",
    "polls",
]

Next, we have to configure our polls.urls in config/urls.py:

from django.contrib import admin
from django.urls import include, path # include is new

urlpatterns = [
    path("polls/", include("polls.urls")), # new
    path("admin/", admin.site.urls),
]

Then, just make sure that there isn't anything in your templates that
does not belong in cast-votes. I had a couple of URLs in
templates/includes and templates/polls/index.html. Those URLS assumed
that I still hadanother reusable app called pages, which exists in
the original django-polls top level directory along with the
django_polls project. But since I haven't added this pages reusable
app to cast-votes, I had to make sure to update them. If, however,
I did want to add that reusable app so that I would have a top
level index page (because right now I don't and neither should you unless you
did something different), then I could keep those URLs which were
specific to django-polls/pages. There were no other "dependencies" on
django-polls.

If I were to package this app and publish it, those URLs would
cause a problem. The other question to ask is, do we want to
include templates in our packaged app or not? A packaged app is
going to be different from a reusable app which we created locally on
our machine and then copied over to another Django project. We have
some control over its behavior in relation to the project, and in
relation to other reusable apps which might be subsequently added.

According to a thread on stackoverflow entitled
Customize templates in a third party Django app,

You can put the template in a separate app within your project. Django looks
for templates in your apps in the order they are defined in INSTALLED_APPS,
and uses the first match: The order of INSTALLED_APPS is significant! For
example, if you want to customize the Django admin, you might choose to
override the standard admin/base_site.html template, from
django.contrib.admin, with your own admin/base_site.html in myproject.polls.
You must then make sure that your myproject.polls comes before
django.contrib.admin in INSTALLED_APPS, otherwise django.contrib.admin’s will
be loaded first and yours will be ignored.

This led me to the updated documentation for Django 5.1 entitled
How to override templates:

In your project, you might want to override a template in another Django
application, whether it be a third-party application or a contrib application
such as django.contrib.admin. You can either put template overrides in your
project’s templates directory or in an application’s templates directory.

And then:

.So create an app, called e.g. social_share_templates, and put it in
INSTALLED_APPS before django_social_share. Then add the template to this folder:

{{project_root}}/social_share_templates/templates/django_social_share/templatetags/post_to_facebook.html

And then:

The reason your current configuration does not work, is that your local app
has the same name as the app in site-packages. If your local app is an actual
python module, you won't be able to use the app in site-packages. Otherwise,
Django just looks for the templates in the app in site-packages.

And then:

So create an app, called e.g. social_share_templates, and put it in
INSTALLED_APPS before django_social_share. Then add the template to this
folder:

This issue(s) in the above thread is similar to what I encountered
when trying to package an existing reusable app following
Creating the official Django Polls app,
among other things.

If you have app and project templates directories that both contain
overrides, the default Django template loader will try to load the
template from the project-level directory first. In other words,
DIRS is searched before APP_DIRS.

To learn more about this, please visit
How to override templates
in the current Django (5.1) documentation.

We choose third party packages primarily for their
functionality/features. If we want to change the looks a bit, we
customize the templates, following the steps described in
How to override templates.

But in my case, I just made a couple of adjustments to fit the
app (module, not package) to the new config project.

To see the original django-polls structure containing both the pages
reusable app and polls reusable app, please visit
django-polls on Github.

Conclusion

In this post, I discussed how I can reuse an app created in one
Django project in another project so that I don't have to
"re-create" it all over again in another project.

Related Resources

Writing your first Django app, part 1: Django documentation
How to override templates: Django documentation
Advanced tutorial: How to write reusable apps: Django documentation
Customize templates in a third party Django app: stackoverflow

Creating the official Django Polls app table of contents: mariadcampbell.com

How to upgrade the Python version in a virtual environment

Maria Campbell — Tue, 14 Jan 2025 21:11:57 +0000

Photo by Mitchell Luo on unsplash.com

Activating the virtual environment
Saving my current dependencies
De-activating the virtual environment
Deleting the current venv folder
Creating a new venv folder
Re-activating the virtual environment
Installing saved dependencies
Conclusion
Related Resources
Related Posts

I was working on a new project today (the official Django Polls app
tutorial as a matter of fact), and I noticed that my virtual environment
was using Python 3.12. But in my project, I am using Python
3.13.0. Using different versions of Python in the virtual environment
vs in the code can create problems and conflicts. I had to upgrade
my version of Python in my venv folder pronto!

Activating the virtual environment

First, I had to make sure that my virtual environment was activated in
my project:

source venv/bin/activate

Saving my current dependencies

Next, I had to make sure to save my application's current
dependencies:

pip freeze > requirements.txt

De-activating the virtual environment

Next, I had to deactivate the virtual environment:

deactivate

Deleting the current venv folder

Next, I had to delete the current venv folder. That is what I
call my virtual environment folder. You might call it
something else!

Creating a new venv folder

Next, I had to create a new venv folder using 3.13 since that is
what I wanted to upgrade to:

python3.13 -m venv venv

Re-activating the virtual environment

Next, I had to re-activate the virtual environment:

source venv/bin/activate

Installing saved dependencies

Next, I had to install my saved dependencies:

pip install -r requirements.txt

And that's it!

Conclusion

In this post, I showed how to upgrade the Python version being used
in a Django application's virtual environment.

Related Resources

How to upgrade Python venv version: stackoverflow

Creating the official Django Polls app Part 8: mariadcampbell.com

How to add tables to React Markdown

Maria Campbell — Tue, 03 Sep 2024 04:57:25 +0000

Example of a table in React Markdown

Tables not supported natively in React Markdown

Tables not supported natively in React Markdown

Recently I was writing an article in React Markdown, and I wanted to add a
table. However, it did not render! I didn't realize until I further researched
the issue that React Markdown does not support adding tables in Markdown
natively. According to an
issues thread in the
React Markdown Github repository from December 22, 2020,

Tables, and all other GFM have moved to a plugin. You can see an example of
usage with tables here: https://github.com/remarkjs/react-markdown#use and the
note in the release notes here:
https://github.com/remarkjs/react-markdown/blob/main/changelog.md#500---2020-10-19

The website accurately reflects that by default, react-markdown follows the
CommonMark standard, which does not have Tables. --
ChristianMurphy commented on Dec 22, 2020

I looked at the example of usage with tables, and it seemed pretty
straightforward. I followed the example and imported the remark-gfm npm
package into my post-content.js file after installing it. Then I added it to
the ReactMarkdown component. But it didn't work. I kept on getting
TypeError Cannot set properties of undefined (setting 'inTable'). I did a
Google Search and came up with a thread on stackoverflow entitled
ReactMarkdown + remarkGfm: everything renders as expected, EXCEPT tables - typeError?.

First I found out that it was only with React Markdown 9.0 that I could use the
latest version of remark-gfm. I however, am using React Markdown 8.0.7.
According to the answer that solved my issue, React Markdown 8.0.7 works with
remark-gfm version 3.0.1.

So I uninstalled my current version of remark-gfm with npm uninstall
remark-gfm (gfm stands for Github Flavored Markdown) and then re-installed
it with npm i remark-gfm@3.0.1 -S. Then I did the following inside my
post-content.js file which is the component that renders the markdown content of
my posts on this site:



import remarkGfm from 'remark-gfm'
import rehypeRaw from 'rehype-raw'
;<ReactMarkdown
    components={customRenderers}
    rehypePlugins={[rehypeRaw]}
    remarkPlugins={[remarkGfm]}
    remarkRehypeOptions={{ passThrough: ['link'] }}
>
    {post.content}
</ReactMarkdown>

I also installed and imported the rehype-raw npm package, and passed
options to remarkRehypeOptions because in the same thread, another user
stated:

Helping hand - I discovered using the remarkGfm had a knock-on effect when
using custom components in react-markdown. Though remarkGfm fixed the table
layout, it stripped content (e.g. class names) from html tags when used in
markdown (which is valid). As such applying remarkRehypeOptions > passThrough
allowed both the tables to render correctly and links to use custom
components. -- Chris GW Green answered Mar 13 at 13:39

Then he added a code snippet of how he added the two packages to
React Markdown:



<Markdown
   remarkPlugins={[remarkGfm]}
   rehypePlugins={[rehypeRaw]}
   remarkRehypeOptions={{ passThrough: ['link'] }}
    ...

Basically the same as the snippet I shared, and his snippet is where
I also got guidance.

I also added some simple styling for my tables in my
post-content.module.scss file:



/* Markdown table styling */
.content table {
    border-spacing: 0 !important;
    border-collapse: collapse !important;
    border-color: inherit !important;
    display: block !important;
    margin: 0 auto !important;
    width: 100% !important;
    max-width: 100% !important;
    overflow: auto !important;
}

.content tbody,
.content td,
.content tfoot,
.content th,
.content thead,
.content tr {
    border-color: inherit !important;
    border-style: solid !important;
    border-width: 2px !important;
    padding: 0.5rem;
}

if you are a next.js and tailwind.css user, I also added a bit of
styling for dark mode in my (global) post-content.scss file:



.dark .content table {
    color: $white;
}

This is what the table I created looks like:

Screenshot of table used in
How to create a fullstack application using Django and Python part 7

Related Resources

Tables not working on website #526: react-markdown Github repository
remarkjs/react-markdown example usage: remarkjs/react-markdown Github repository
ReactMarkdown + remarkGfm: everything renders as expected, EXCEPT tables - typeError?; stackoverflow

How to create a fullstack application using Django and Python Part 5

Maria Campbell — Thu, 29 Aug 2024 02:12:19 +0000

Photo by CHUTTERSNAP on unsplash.com

This post was originally published on my personal blog mariadcampbell.com.

Important Note: Before committing anything to Git or pushing
anything to remote, please visit
How to create a fullstack application using Django and Python Part 4
where I discuss how to add the python-dotenv package to the Django
site and why it is crucial to do it. This article assumes you have a
working knowledge of Git.

Changing a Django project name after it has already been migrated
Researching the name changing issue
Changing old project name to new project name throughout the Django site
Running the env | grep django command
- Breaking down the env | grep django command
Related Resources
Related Posts

Changing a Django project name after it has already been migrated

When I first created the project for this Django site, I did not
think much about the project name, and named it basic_django_web_page.
I named the root directory of the site basic-django-web-page. But after
already having made migrations (makemigrations) and then migrated the
site (migrate), I wanted to change the root directory of the Django
site to django-boards, and the project name to django_boards. It made
more sense and was more consistent with the rest of the
site namespaces. I had to change both high level project directory to
django_boards and the porject subdirectory to django_boards as well.

But how was I going to do this?

Researching the name changing issue

I had never changed a project name after making model migrations, but
I was determined to make the name change so that I would not have to
re-create the site. That simply would have been a waste of time.

I came across all sorts of solutions which just didn't work, so I
won't even bother mentioning them. Then I came across a thread on
stackoverflow that gave me the answer(s) I was looking for!

Changing old project name to new project name throughout the Django site

I typed in the old project name in the Search (eyeglass icon) field
in Visual Studio Code to quickly find out where it came up in the
project code base:

It appeared in .gitignore.
It appeared in manage.py.
It appeared in asgi.py.
It appeared in settings.py.
it appeared in urls.py.

I removed all instances of basic_django_web_page and replaced it with
django_boards. This included any reference to the project name in
string comments! Those references count too.

After I did all that, committed the changes, pushed them to
Github, and then tried to run the development server, it worked.

But... when I went back later to the same thread where I found my
solutions, I learned that there was still more checking I should do.

Running the env | grep django command

I also learned in the stackoverflow thread (listed in Related Resources)
that I should run the env | grep django command to see if the old
project name was lingering anywhere in the virtual environment (venv).
The following was returned in Terminal:

PATH=/Users/mariacam/Python-Development/basic-django-web-page/venv/bin:/Users/mariacam/.pyenv/shims:/Users/mariacam/.pyenv/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/Users/mariacam/mongodb/bin:/Applications/Postgres.app/Contents/Versions/latest/bin:/Library/PostgreSQL/10/bin:/Users/mariacam/.rbenv/bin:/Users/mariacam/.yarn/bin:/Library/Frameworks/Python.framework/Versions/3.12/bin:/Users/mariacam/.nvm/versions/node/v20.15.0/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/mariacam/.rvm/bin
PWD=/Users/mariacam/Python-Development/django-boards/django_boards
OLDPWD=/Users/mariacam/Python-Development/django-boards
VIRTUAL_ENV=/Users/mariacam/Python-Development/basic-django-web-page/venv

The new project name was recognized, and was also set in all the
right places in the code base, i.e., including DJANGO_SETTINGS_MODULE in
settings.py,but the original root directory name did appear in the
VIRTUAL_ENV variable.

Breaking down the env | grep django command

The env | grep django command is used to filter environment variables related
to Django.

The env command lists all the environment variables in the current shell session.
| (pipe) operator pipes the output of the env command to the grep command.
grep django searches through the output for lines that contain the string "django".

The env | grep django command displays all environment variables that
include "django" in their names or values. This is useful when we want
to check any environment settings related to Django.

All I had to do to fix the value of VIRTUAL_ENV was the following:

I opened up venv/bin/activate in vim with the following command:

vim venv/bin/activate

Then I added the following at the bottom of the file:

export VIRTUAL_ENV=/Users/mariacam/Python-Development/django-boards/venv

Then I ran the env | grep django command again, and the following was returned:

PATH=/Users/mariacam/Python-Development/basic-django-web-page/venv/bin:/Users/mariacam/.pyenv/shims:/Users/mariacam/.pyenv/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/Users/mariacam/mongodb/bin:/Applications/Postgres.app/Contents/Versions/latest/bin:/Library/PostgreSQL/10/bin:/Users/mariacam/.rbenv/bin:/Users/mariacam/.yarn/bin:/Library/Frameworks/Python.framework/Versions/3.12/bin:/Users/mariacam/.nvm/versions/node/v20.15.0/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/mariacam/.rvm/bin
PWD=/Users/mariacam/Python-Development/django-boards
OLDPWD=/Users/mariacam/Python-Development/django-boards/django_boards
VIRTUAL_ENV=/Users/mariacam/Python-Development/django-boards/venv

Success! My VIRTUAL_ENV variable value was updated to the correct path!

And that is how I changed the name of my Django project from
basic_django_web_page to django_boards.

Related Resources

Is there an easy way to rename a Django project?: stackoverflow

How to create a fullstack application using Django and Python Table of Contents

Vim essentials in Linux

Maria Campbell — Tue, 20 Aug 2024 22:00:51 +0000

This post was originally published on my personal blog mariadcampbell.com.

So why this article?
What does Vim stand for?
Configuring Vim
The vim command
Vim modes
- Normal mode
  - The (lowercase) gg shortcut
  - The (uppercase) G shortcut
  - The # (number) G shortcut
  - The (lowercase) h shortcut
  - The (lowercase) j shortcut
  - The (lowercase) k shortcut
  - The (lowercase) l shortcut
  - The # (number) j shortcut
  - The # (number) k shortcut
  - The (lowercase) w shortcut
  - The (lowercase) b shortcut
  - The (lowercase) e shortcut
  - The (uppercase) W shortcut
  - The (uppercase) B shortcut
  - The (uppercase) E shortcut
  - The 0 (zero) shortcut
  - The ^ (caret) shortcut
  - The (dollar sign) $ shortcut
  - The (lowercase) r shortcut
  - The (lowercase) x shortcut
  - The (uppercase) X shortcut
  - The (lowercase) dw shortcut
  - The (lowercase) cw shortcut
  - The (lowercase) s shortcut
  - The (uppercase) S shortcut
  - The (uppercase) D shortcut
  - The (lowercase) dd shortcut
  - The (uppercase) C shortcut
  - The (lowercase) yy shortcut
  - The (lowercase) p shortcut
  - The (uppercase) P shortcut
  - The (lowercase) u shortcut
  - The Control + r shortcut
  - Repeating commands
    - Repeating a command using a count
- Insert mode
  - Entering Insert mode
    - The (lowercase) i shortcut
    - The (uppercase) I shortcut
    - The (lowercase) a shortcut
    - The (uppercase) A shortcut
    - The (lowercase) o shortcut
    - The (uppercase) O shortcut
    - Switching from Insert mode into Normal mode
- Visual mode
  - Entering Visual mode
    - The (lowercase) v shortcut
    - The (uppercase) V shortcut
    - The Control + v shortcut
- Command mode
  - Asking Vim for help
  - Other Command mode commands
The vimtutor
Related Resources

So why this article?

Good question! I have been using Vim in macOS for a very long time, but
primarily to write Git commit messages. Most of my file editing has
taken place inside Visual Studio Code.

Then I started working in Linux, but in a virtual environment
(VirtualBox) installed on Windows 11. The memory and disk space I
allocated to it was much smaller than what I have available on macOS,
and Visual Studio Code is known for being memory greedy. I did install it in
Linux Mint, but it severely slowed down the OS and even crashed from to
time to time. That is when I decided to use the Vim text editor
instead.

By default, Vim did not cut it for what I wanted to accomplish, so
I did some research to learn more about it, how I could configure it to
help me accomplish what I wanted to accomplish, and better navigate
Vim in general.

Well, I found out that I can basically use it like any other editor,
including Visual Studio Code. It was a matter of mastering it. But
there is another aspect to this.

In Linux Mint inside VirtualBox, for me, the default Terminal is on the
small side. My laptop screen is not the largest and the Linux Mint
window in VirtualBox is not the largest either. The key input using the
laptop keypad is not the most fantastic experience in Windows. So what
did I do about that?

It was serendipitous. In my research, I accidentally came across a new
terminal program called Warp. Currently, it works in the Linux and
macOS Unix operating systems. Warp for Windows is also coming out
soon, but has not been released yet.

Basically, Warp is a modern, Rust-based terminal with AI built in so
you and your team can build great software faster.

All the Terminal screenshots and Gifs I use here were taken in Warp.

i love it. Despite having AI builtin, there still is a significant
learning curve. It does detect and therefore the tools we use in our
native OS, such as shell. I use ZSH in macOS, so Warp uses ZSH. In
Linux, I use Bash, so Warp uses Bash there. I am never going back to
iTerm2 in macOS or Linux Mint's default Terminal program. Warp all the
way!

What does Vim stand for?

Vim stands for Vi iMproved. Vi is frequently a symbolic link to Vim,
the enhanced version of Vi. If you have vim installed and access to
the vim command, you also have access to the vi command. When I
installed Vim in Linux Mint, I gained access to both the vim and vi
command.

Configuring Vim

To make my life much easier when working with Vim, I configured it
using a file I created (which was not included by default) called
.vimrc inside my home directory (/home/maria in Linux and
/Users/mariacam in macOS). I added the following to the .vimrc file:

# Disable compatibility with vim which can cause unexpected issues.
set nocompatible
set autoindent
# Set tab width to 4 columns.
set tabstop=4
# Use space characters instead of tabs.
set expandtab
# Set shift width to 4 spaces.
set shiftwidth=4
# Add numbers to each line on the left-hand side.
set number
# Highlight cursor line underneath the cursor horizontally.
set cursorline
# Highlight cursor line underneath the cursor vertically.
set cursorcolumn
# Do not save backup files.
set nobackup
# While searching though a file incrementally highlight matching characters as you type.
set incsearch
# Do not wrap lines. Allow long lines to extend as far as the line goes.
set nowrap
# Ignore capital letters during search.
set ignorecase
# Override the ignorecase option if searching for capital letters.
# This will allow you to search specifically for capital letters.
set smartcase
# Show partial command you type in the last line of the screen.
set showcmd
# Show the mode you are on the last line.
set showmode
# Show matching words during a search.
set showmatch
# Use highlighting when doing a search.
set hlsearch
# Set the commands to save in history default number is 20.
set history=1000
# Enable auto completion menu after pressing TAB.
set wildmenu
# Make wildmenu behave like similar to Bash completion.
set wildmode=list:longest
# Wildmenu will ignore files with these extensions.
set wildignore=*.docx,*.jpg,*.png,*.gif,*.pdf,*.pyc,*.exe,*.flv,*.img,*.xlsx
# Enable type file detection. Vim will be able to try to detect the type of file in use.
filetype on
# Enable plugins and load plugin for the detected file type.
filetype plugin on
# Load an indent file for the detected file type.
filetype indent on
# Turn syntax highlighting on.
syntax on

This immediately made navigating files in Normal mode and
creating content in Insert mode so much easier!

If I open my .vimrc file using the vim .vimrc command in macOS
iTerm2, it now looks like the following:

If I open my .vimrc file using the vim .vimrc command in macOS Warp
Terminal, it now looks like the following:

Highlighting colors and a few other details may differ slightly when
using Warp Terminal. However, as shown above, these configurations still
work well with Warp and do not cause any conflicts since Warp works
with Vim.

The vim command

The first command to learn regarding Vim is the vim command. In order
to open a file in Vim, I run the following in Terminal:

# this command opens up a file called history.txt in Vim
vim history.txt

Vim modes

The are 4 main modes in vim. Normal mode, Insert mode, Visual mode,
and Command mode. According to Warp documentation, there is also
Replace mode (which actually is part of Normal mode; Replace mode is
redundant), Binary mode, and Org mode. Binary and Org mode fall
under more advanced Vim features and will not be covered here.
However, information related to both is available in the
Related Resources located at the bottom of this article.

Normal mode

Normal mode is the default mode when we enter Vim. It is the mode that
allows us to move around a file. Normal mode can be accessed from
other modes by pressing the esc key.

The (lowercase) gg shortcut

When I press the g key twice, gg, I am taken to the beginning of a
file.

The (uppercase) G shortcut

When I press the G key (Shift key + G key), I am taken to the end
of a file.

The # (number) G shortcut

I love this one. # is a placeholder for the line number that you
want to go to. Let's say I want to go to line 15 of a file in Vim,
I would go into Normal mode by pressing the esc key, then would type
15G (1 key + 5 key + Shift key + G key), and I would be taken to the
beginning of line 15 of a file in Vim.

The (lowercase) h shortcut

When I press the h key, the cursor moves one character to the left.

The (lowercase) j shortcut

When I press the j key, the cursor moves one line down.

The (lowercase) k shortcut

When I press the k key, the cursor moves one line up.

The (lowercase) l shortcut

When I press the l key, the cursor moves one character to the
right.

The # (number) j shortcut

This is similar to the # (number) G shortcut.
When I press the Shift key + 6 key + j key, for example, the cursor
moves 6 lines down.

The # (number) k shortcut

This is similar to the # (number) G shortcut.
When I press the 8 key + (lowercase) k key, for example, the cursor
moves 8 lines up.

The (lowercase) w shortcut

When I press the w key, the cursor moves to the beginning of the
next word.

The (lowercase) b shortcut

When I press the b key, the cursor moves to the beginning of the
previous word.

The (lowercase) e shortcut

When I press the e key, the cursor moves to the end of a word.

The (uppercase) W shortcut

When I press the Shift key + w key, the cursor moves to the
beginning of the next word after a whitespace. This is basically the
same as the (lowercase) w shortcut.

The (uppercase) B shortcut

When I press the Shift key + b key, the cursor moves to the
beginning of the previous word before a whitespace. This is basically
the same as the (lowercase) b shortcut.

The (uppercase) E shortcut

When I press the Shift key + e key, the cursor moves to the end of a
word before a whitespace. This is basically the same as
the (lowercase) e shortcut.

The 0 (zero) shortcut

When I press the 0 key, the cursor moves to the beginning of a line.

The ^ (caret) shortcut

The ^ (caret) shortcut is the same as
the 0 (zero) shortcut. When I press the Shift
key + 6 key, the cursor moves to the beginning of a line.

The (dollar sign) $ shortcut

When I press the Shift key + 4 key, the cursor moves to the end of a
line.

The (lowercase) r shortcut

When I move the cursor over a particular character I want to
replace, I press the r key, and then I press the key of the
character I want to replace it with.

The way this shortcut works is when Imove the cursor over the
character I want to replace, and then press the r key, the character
I want to replace is first replaced by an r character, and then when I
press the character (key) I want to replace it with, it replaces
the r that appeared when I executed
the (lowercase) r shortcut.

The (lowercase) x shortcut

This shortcut is similar to
the (lowercase) r shortcut. When I move the
cursor over the character I want to delete, I then press the x key,
and the character is deleted. This shortcut is also referred to as the
"Delete button".

The way this shortcut works is when I move the cursor over the
character I want to delete, and then press the x key, the character
I wanted to delete is deleted. But if I want to bring back the
character I have deleted, I press the (lowercase) u key which
executes the (lowercase) u shortcut.

The (uppercase) X shortcut

This shortcut (aka the "Backspace button") deletes characters to the
left of the cursor, but not the character it is highlighting (if it
is highlighting one). So if you delete an entire line using
the (uppercase) X shortcut, except for the
character the cursor is highlighting, you can press the (lowercase)
x key, and the character will be removed.

The (lowercase) dw shortcut

When I highlight a word, and then press the d followed by the w key,
the word is deleted. And if I want to bring back that word, I would
press the (lowercase) u key to undo that edit. If, however, I
wanted to replace the word I deleted, I would want to use
the (lowercase) cw shortcut.

In order to highlight a complete word, I have to enter Visual mode. To
switch from Normal Mode to Visual mode, I first press the esc key and
then the (lowercase) v key. The esc key takes me out of Normal mode,
and the (lowercase) v key takes me into Visual mode. Then, I use
either the forward arrow key to highlight the word to the right of the
cursor, making sure to end highlighting after the last character of the
word, or the left arrow key to do the same in the opposite direction.

The (lowercase) cw shortcut

When I highlight a word, and then press the c key followed by the
w key, the word is deleted, and I then replace it with another one.

In order to highlight a complete word, I have to enter Visual mode. To
switch from Normal Mode to Visual mode, I first press the esc key and
then the (lowercase) v key. The esc key takes me out of
Normal mode, and the v key takes me into Visual mode. Then, I use
either the forward arrow key to highlight the word to the right of the
cursor, making sure to end highlighting after the last character of the
word, or the left arrow key to do the same in the opposite direction.

The (lowercase) s shortcut

When I highlight a character with the cursor and then press the s
key, I then press the key of the character I want to replace it
with.

The (uppercase) S shortcut

When I highlight the location in a line where I want to start the
edit of my line, and then press the Shift key + s key, it removes
that content, and then I can type in what I want to replace it
with.

The (uppercase) D shortcut

When I place my cursor where I want to start deleting a line, and
then press the Shift + d key, it deletes the line from that point to
the end of the line.

The (lowercase) dd shortcut

When I select the point from which I want to delete a line using
the cursor, I then press the d key followed by pressing the d key
again, and the line from the location of the cursor on, is deleted.
If I place the cursor at the beginning of the line, the entire line
is deleted.

The (uppercase) C shortcut

This is similar to the (uppercase) D shortcut,
but when I press the Shift key + c key, after the (part of) the
line has been deleted, I can replace it with new content.

The (lowercase) yy shortcut

This works similarly to
the (lowercase) dd shortcut, except that
instead of the line being deleted, it is copied. I first place the
cursor where I want to start copying the line, and then I press the
(lowercase) y key followed by pressing the (lowercase) y key
again, and the part of the line I selected (or the complete line if
I placed the cursor at the beginning of the line) is copied to the
clipboard.

The (lowercase) p shortcut

After I have copied a line (or part of it) as per
the (lowercase) yy shortcut, I press the p
key, and the line is pasted below the line I copied.

The (uppercase) P shortcut

After I have copied a line (or part of it) as per
the (lowercase) yy shortcut, I press the Shift
key + the p key, and the line is pasted above the line I copied.

The (lowercase) u shortcut

When I press the u key, it undoes the last change I made. I can
also keep on pressing the u key in order to keep on undoing previous
changes. Once I am happy with the current state of my file, I can
type :w so that I save this acceptable state. If I want to exit
Vim after saving the acceptable state, I would simply press the esc
key followed by the : (Shift key + (;) semi-colon key), and I
would be taken back to my Terminal prompt.

The Control + r shortcut

The Control key + r key undoes my undo I executed with
the (lowercase) u shortcut. And if I want to
revert to my latest undo, I just press the (lowercase) u key
executing the (lowercase) u shortcut.

Repeating commands

Repeating a command using a count

Vim supports shortcut repetition in Normal mode. Instead of entering
the same shortcut multiple times to repeat the desired action, I can
prefix the same shortcut with the number of repetitions. To delete 6
lines, I would highlight the beginning of the line I wanted to start
my deletion with the cursor, and then I would press the 6 key
followed by the d key and the d key again (6dd). This would
delete the line where the cursor is located and 5 lines after that.

To repeat the (lowercase) yy shortcut, I would
highlight the beginning of the line I wanted to start my copying
with the cursor, and then I would press the 6 key (again,
for example) followed by the y key and the y key again (6yy).
Next, I would move the cursor below the current line and then move it
5 times more, for a total of 6 lines, stopping at the last line I
want to copy (the cursor should appear to "underline" that line).
This would copy the line where the cursor began and 5 lines after
that. Lastly, I would press the (lowercase) p key, not moving the
cursor, and this would paste the 6 lines I copied.

The screenshot below shows the first line which I wanted to
start copying from and where I placed the cursor at the beginning of
that line, and then I pressed 6yy (6 key + y key + y key) at the
beginning of the line where the cursor is located:

The screenshot below shows the end line of the line block I want to
copy. I moved to this line after I had pressed 6yy (as described
above the first screenshot). I had to take the cursor to the line
where I wanted to end the copying process.

Then I pressed the p key, and the 6 lines I copied are pasted below
the lines I copied:

Insert mode

Insert mode allows me to type/insert characters just like a regular
text editor. I can enter Insert mode by using an insert shortcut from
Normal mode.

Entering Insert mode

There are several ways of entering Insert mode.

The (lowercase) i shortcut

When I press the i key, I am switched into Insert mode. I know I am
in Insert mode because -- Insert --- appears at the bottom of the
window.

The (uppercase) I shortcut

When I press the Shift key + i key, I switch into Insert mode, and
the cursor moves to the beginning of the line (if it is not already
there).

The (lowercase) a shortcut

[The (lowercase) a shortcut] behavior is almost the same as the
(lowercase) i shortcut. The only difference is
that when I press the a key, and when -- Insert --- appears at the
bottom of the window, the cursor moves from the beginning of the
line to the next character to the right.

The (uppercase) A shortcut

When I press the Shift key + the a key, I switch into Insert mode,
and the cursor moves to the end of the line.

The (lowercase) o shortcut

After I press the o key, I switch into Insert mode, and the cursor
moves down to the second line, creating a new line space. The contents
of the second line is moved down to the third line.

The (uppercase) O shortcut

When I press the Shift + o key, I switch into Insert mode, and the
first line moves down to the second line, leaving a line space on the
first line.

Switching from Insert mode into Normal mode

In order to switch from Insert mode into Normal mode, I press the
esc key. And if I am ever unsure whether I am in Normal mode or not,
I press the esc key to make sure.

Visual mode

I use Visual mode to select text, similar to clicking and dragging
with a mouse. Selecting text allows shortcuts to apply only to the
selection, such as copying, deleting, replacing, etc.

Entering Visual mode

To make a text selection, first I press the (lowercase) v key, and
this will also mark the starting selection point. Then I move the
cursor to the end selection point, and Vim provides a visual highlight
of the text selection.

The (lowercase) v shortcut

This shortcut is also known as the Visual mode visual subtype.

When I want to enter Visual mode visual subtype, I first press the esc
key to exit whatever mode I was in, and then I press the v key, this
switches me into Visual mode, and will also mark the
start selection point. When I move the cursor across the the
first line, the cursor moves character by character.

Next, I can use the Up arrow or the (lowercase) k key to
select lines going up. As mentioned previously, no matter what the
difference in line lengths, the lines are completely selected. Same
with when I use the Down arrow key or (lowercase) j key to
select lines going down.

The (uppercase) V shortcut

This shortcut is also known as the Visual mode line-wise visual subtype.
It always selects full lines.

When I press the Shift key + v key, I switch into Visual mode, and
this makes text selections line by line. This is great for when I
want to select a block of text in which the lines are
different lengths. After I select the first line, and then move the
cursor down (or the Up arrow key to move the cursor up), it will
select the whole line no matter the difference in line length.

The Control + v shortcut

This shortcut is also known as the Visual mode block-wise subtype. it
selects any rectangular selection.

When I press Control key + (lowercase) v key, I am switched to the
Visual mode block-wise subtype. So far, I have not had
appropriate opportunity to use this subtype. So far, contrary to
popular opinion, I find it somewhat limiting.

As opposed to the Visual mode visual subtype or the
Visual mode line-wise visual subtype, the shortest line is selected and
kept when either selecting lines down or up. This is because lines
and columns are being selected at the same time, and the columns consist
oflines of equal width.

Command mode

Asking Vim for help

If I need to find out how to do something in Vim, I can access Vim
help by running the :help command. I first make sure I am in
Normal mode by pressing the esc key, and then I press the Shift
key + (;) semi-colon key, and then I type "help". And the following
appears:

Then I press the Return key and the following appears:

I could also search for specific help with the :help command.
For example, I could type :help visual.txt:

When I want to exit the :help or :help visual.txt command, I first
press the esc key followed by :q! and then the Return key, which
takes me out of the :help visual.txt command. However, I am still in
Command mode. If I want to quit completely out of Vim, I simply
hit the Return key again, and am taken back to the Terminal prompt.

If I want to remain in Vim, but want to exit out of Command mode,
instead of pressing the Return key a second time, I press the
(lowercase) i key and am taken into Insert mode. If I want to
switch into another mode like Normal mode, for example, I press the
esc key. This way, I stay in Vim.

Other Command mode commands

Other Command mode commands (some of which have already been
covered):

# Quit file
:q
# write changes to file
:w
# Save and quit
:wq
# Save and quit
:x
# Quit forcefully
:q!
# Save and exit forcefully
:wq!
# Go to first line of file
:1
# Set numbers to lines
:set nu
# Remove numbers from lines
:set nanu
# Specified line number, Same as :1 command, just a different number.
:<Specific line number>
# The command output will paste in current cursor position.
:r !date
# Executes shell command "ls" of current working directory in Terminal
:!ls

There is a lot more to Command mode, but this is a good start!

You can dig deeper in Vim by checking out the various Related Resources.

The vimtutor

By default, the Vim install includes a tutorial called vimtutor. It is
meant to help us learn the Vim basics hands-on. We can start the
vimtutor by running the following command in Terminal:

vimtutor

Related Resources

An introduction to the vi editor: RedHat
vim: warp
Vim Essentials: Tips and Tricks for Boosting Productivity: upspir
Vimrc Configuration Guide - How to Customize Your Vim Code Editor with Mappings, Vimscript, Status Line, and More: by Brandon Wallace, freecodecamp
Vim Editor Modes Explained: freecodecamp
A Guide to Vim Visual Mode: builtin

Setting your default browser via Command Line in macOS

Maria Campbell — Mon, 19 Aug 2024 09:57:03 +0000

Photo by Designecologist on pexels.com

This post was originally published on my personal blog mariadcampbell.com.

Installing the Homebrew package defaultbrowser
brew install defaultbrowser
Running the defaultbrowser safari command

Installing the Homebrew package defaultbrowser

In order to set my default browser in macOS via Command Line, I first
had to install the Homebrew package called defaultbrowser.

First, I ran the following commands, one after the other:

brew update
brew upgrade

This is similar to what we do in Linux Mint when we run
sudo apt update and sudo apt upgrade to make sure that all our
packages are up to date before installing a new one. We have to do
the same with Homebrew.

brew install defaultbrowser

Next, I run the following command to install the defaultbrowser
package:

brew install defaultbrowser

Running the defaultbrowser safari command

After it was successfully installed, I quit the active Terminal window
and opened up a new instance. And there, I ran the following command to
make Safari my default browser:

defaultbrowser safari

And that was it!

No more need to go into browser settings searching for the location
where to set a particular browser as your default browser. You can just
set it by typing a simple two word command in Terminal!

Clearing Terminal history in Linux and why it is important to do on occasion

Maria Campbell — Sat, 17 Aug 2024 19:13:44 +0000

Photo by Enes Bayraktar on pexels.com

This post was originally published on my personal blog mariadcampbell.com.

What is the history command?
history is not actually a command
history
Removing history
- Deleting a command by line number
- history -c
- Manually removing the contents of .bash_history
- Clearing .bash_history using the echo command
bash history, privacy and security
Related Resources

What is the history command?

The history command in Linux (and macOS) stores a list of commands
that have been used in Terminal sessions, and it permits us to reuse
them instead of retyping them.

history is not actually a command

If I run which history in Terminal, nothing is stdout. This confirms
that history is not actually a command. history is a built-in keyword
of our shell (Another example is the cd command. It also is a builtin
keyword and not a command). And because history is written into the
particular shell we are using at any given time, there can be a
difference in its behavior across shells. But since I use bash in
Linux, I will be discussing bash-specific history behavior in my
particular Linux distro (Linux Mint).

history

If I run history in Terminal, I get back 428 lines, each line containing
a command I have run in Terminal. The following is a sneak peak at
history stdout:'

  1 ls
  2 cd Desktop
  3 ls
  4 cd cron-job-scripts/
  5 ls
  6 mailx
  7 sudo apt update
  8 sudo apt upgrade
  9 sudo apt install mailx
  ...
428 history

If I wanted to run a specific command using its line number, I would
run the following:

!84

Which would return the following:

cd desktop-backup/

This is the command at line 84 in (Terminal) history. I could also
access and run this command by running the following:

!cd desktop-backup/

Sometimes, as in this case, we get back something like the
following:

cd desktop-backup/ desktop-backup/
bash cd: too many arguments

So I tried another one that does not result in any ambiguity:

!clear

It runs the clear command, clearing the Terminal window. Using !
before the command itself prompts history to search for the last command
that matches the pattern I provided. In this case, it is clear.

But I digress. Let's get to the task at hand.

Removing history

There are several ways to remove some or all commands saved to history.

Deleting a command by line number

If I want to delete a command saved to history by line number, I would
run the following command:

history -d 423

This removes the command at line 423. This is a great command to know
in case if you have mistyped a command, for example, and want to
remove it from history because it is essentially useless. But it can
also be used to remove specific commands containing
sensitive information. Why? What ifyou had to use history or
some other related tool or command in a presentation, and you wanted
to make sure that nothing sensitive would appear on the screen, and you
didn't want to completely remove your history. This would be one way
to do that.

history -c

The history -c command removes the contents of a specific Terminal
session's history. If I run history -c and then check to see if the
contents of my Terminal session's history was indeed completely
removed, I would run history again, and something like the following
would be returned:

1 history

Manually removing the contents of .bash_history

history stores the commands run in Terminal in a file called
.bash_history, which is located in a user's home directory. If, after
running history -c, I want to double check if all my history has
actually been removed, I can run vim .bash_history to open up the file
in Vim. And something like the following would appear:

# The contents of .bash_history contained 426 lines. I am truncating it.
...
which diff
diff -s secret_message.txt decrypted_super_secret.txt
sha512sum secret_message.txt

history -c only clears the history of a specific Terminal session, but
not the entire contents of .bash_history itself. Some articles state that
it completely removes all your history, but it does not. After running
history -c, your .bash_history still contains the history of the
commands you have run in Terminal.

If I wanted to manually remove the contents of .bash_history, I would
have to open the file and manually delete the contents of the file.
I could open the file using open .bash_history inside my home directory
where the file resides, Control + A the file contents, and then hit the
delete key and remove the file contents.

I could also run vim .bash_history and be taken into the Vim interface.
There, I would do the following:

# First I go into Vim normal mode by hitting the `esc` key
# Next, I enter command mode by hitting Shift key + : (colon)
# To Select All, I hit the Shift Key + % (5 key) after the colon (:)
# to delete everything, I then hit the D key after %
# To save my changes, I hit the esc key followed by Shift key + : (colon) and then the X key. This saves my changes and takes me out of Vim.

If, after deleting the entire contents of .bash_history,
subsequent commands are not saved to .bash_history (it remains empty),
run the following command:

history > .bash_history

Then open up .bash_history, and you should see your stored Terminal
history reappear. That is because you have redirected history as
stdout to the .bash_history file.

Next, to doubly make sure that everything is working as it should,
run a few commands in Terminal, and then re-open .bash_history to
see if those commands are being saved to .bash_history. When I
did this and re-opened .bash_history, I saw that new commands were not
being added to .bash_history. Even when I quit Terminal and started a
new session. So I had to do the following to do a history "reset":

# I ran this inside my home directory /home/maria where my .bash_history resides
rm .bash_history
touch .bash_history

Once I re-created the .bash_history file, I saw that Terminal history
was saved to .bash_history, but commands from a Terminal session would
save to the .bash_history file when I would exit out of a Terminal
session and start a new one. But it worked just fine and as
expected!

Clearing .bash_history using the echo command

In order to remove to complete contents of the ~/.bash_history file, I
ran the following command:

# I did not have to add ~/ in front of .bash_history because I ran the command inside my home directory
echo > .bash_history

And when I opened up .bash_history using open .bash_history, the file
was completely empty. This is the ONLY command that successfully removed
the contents of my .bash_history file!

bash history, privacy and security

Clearing one's bash history is not just about keeping things "clean".
it's also about safeguarding one's privacy and security. By clearing
our bash history on a regular basis, we can help protect
sensitive information that we may have used in a command, such as
passwords or other confidential data.

Related Resources

How to use the history command in Linux: by Steve Morris, opensource.com
Select all in Vim / Vi: warp.dev
Clear Bash History: Bash Shell and Command Line Guide: I/O Flood
How to Clear the Terminal History in Linux: Geeks for Geeks

Setting up and using the mutt email client in Linux

Maria Campbell — Thu, 15 Aug 2024 13:41:29 +0000

This post was originally published on my personal blog mariadcampbell.com.

What is mutt?
Installing mutt
Sending an email locally to another user which contains an attachment
Other user receives email and saves email attachment locally
Asymmetric encryption and decryption series

What is mutt?

mutt is a powerful Command Line email client that sends and receives
emails via Terminal. I use it in addition to mailx, because unlike
mailx, it is able to send real email attachments as well as save
those attachments on a user's local machine.

mutt supports MIME, GPG, PGP, and threading, making it a
powerful tool for managing emails directly from the Linux Command Line.
mutt also allows system administrators to automate and streamline their
workflows with automated notifications. Email plays a critical role in
system security and can be used to deliver security alerts, confirm user
actions, and even recover lost passwords. By properly managing emails
using mutt, we can enhance the security of our Linux system.

There are many other uses for mutt. To learn more, please visit the
article entitled Mastering Mutt: How to Install Mutt Command in Linux.

Installing mutt

One thing to note: in whichever directory we initialize mutt is the
default directory where email attachments are saved.

mutt is not native to Linux. We have to install it. I am on the
Ubuntu derivative Linux Mint, so I can install it with the
following command(s):



sudo apt update
sudo apt upgrade
sudo apt install mutt

Since I only want to use it locally because I have Linux Mint
installed with VirtualBox and only have so much virtual (and hard)
disk space to work with, I decided to pass up on using an external
(gmail) email address to send and receive emails. My main reason for
wanting to use mutt was because of its ability to send
email attachments and save received attachments locally. There are many
other powerful features available, but this is the feature that grabbed
my attention.

Sending an email locally to another user which contains an attachment

I want to send a file to another user on the local network in Linux
using mutt. I would take the following steps:

First, I would cd into the directory where I first initialized mutt. In my case, it was my home directory, /home/maria.
Next, I would determine which email attachment I want to send to the other user.

Next, I will send a text file called email_attachment.txt to local user
magdala, which contains the text
This is some dummy text for the mutt email attachment demo I am creating for my post entitled "Setting up and using the mutt email client in Linux."
I run the following command in Terminal:



mutt -s "Sending Magdala the email_attachment.txt" -a email_attachment.txt -- magdala@maria-VirtualBox

This opens up the mutt interface in the nano text editor. it looks
something like the following:

Then I hit the Return key, and something like the following appears:

Next, I hit Return and the following appears:

The next part is very important to follow correctly. After I have
completed the body of my email, I hit Control + O (not zero) key and
then the Return key, and then the following appears:

As shown at the top of the window, I hit the y key to actually send
the email to user magdala. Then, at the bottom of the window, "Mail
sent" appears, and then I am taken back to the Terminal command prompt.

Other user receives email and saves email attachment locally

Next, user magdala opens her emails using the mutt command, and
something like the following appears:

Next, user magdala makes sure to select the email which contains the
attachment she wants to save to her local machine using the Up or
Down arrow key, and then she hits the V key. This results in
something like the following:

Next, user magdala hits the S key, and that is when the text
"Save to file: email_attachment.txt" appears. And then the following
appears after that:

Next, user magdala hits the Q key, and is taken back to the Terminal
command prompt:

And as also shown in the screenshot, she then runs the ls command to
make sure that the email_attachment.txt file has been saved to her home
directory. And it was!

We have now covered the basics of sending, receiving, and saving
email attachments using mutt.

Asymmetric encryption and decryption series

Cron job that creates backups of a directory in Linux

Maria Campbell — Thu, 08 Aug 2024 03:26:00 +0000

Photo by Mikhail Nilov on pexels.com

This post was originally published on my personal blog mariadcampbell.com.

I just finished creating a cron job that backs up my Desktop directory daily in my Linux Mint OS. The name of the backup includes the date and time of the backup.

Creating the desktop-backup directory and the desktop_backup.sh shell script
Creating the delete_backups.sh shell script
Adding the shell scripts to the crontab file
Related Resources

Creating the desktop-backup directory and the desktop_backup.sh shell script

First, I created a backup directory called desktop-backups in my home directory (/home/maria), and then I created a shell script called desktop_backup.sh located in /home/maria/Desktop/cron-job-scripts/. And then I added the following:

#!/bin/bash

source_dir="/home/maria/Desktop"
backup_dir="/home/maria/desktop-backup"
timestamp=$(date +%Y%m%d%H%M%S)
backup_file="backup_$timestamp.tar.gz"
tar -czvf "$backup_dir/$backup_file" "$source_dir"

The first line in the script is very important. #! is referred to as shebang, and it tells the system which interpreter/command to use to execute the commands written inside the scripts. The interpreter here is bash, and the path to it is /bin/bash, which follows #!. #! is
interpreted by the execve(2) system call (which executes programs).

Next, and most important, is to change file permissions for the desktop_backup.sh file. By default, a newly created file does not contain execute permissions, which is necessary for executing shell script files. So next, I have to run the following in Terminal to add
execute permissions to desktop_backup.sh from inside the directory where it resides:

chmod +x desktop_backup.sh

chmod stands for change mode.

Then I check to make sure that execute permissions were added to desktop_backup.sh by running the ls -l command in Terminal, and the following is returned as a result:

-rwxrwxr-x 1 maria maria 208 Aug 7 13:10 desktop_backup.sh

When I create the delete_backups.sh file (coming up), I will have to change permissions in the same way as well.

If I run date +%Y%m%d%H%M%S in Terminal, something like the following is returned:

202400807161028

202400807 is the year, month and day. 161028 is the hour, minutes, and seconds in 24 hour format. After I run the shell script, something like the following appears in the desktop-backup directory:

backup_202400807161028.tar.gz

If I am inside the cron-job-scripts directory where desktop_backup.sh
resides, I run the following in Terminal:

./desktop_backup.sh

Which is how a shell script is run in Terminal. If I am not inside the
directory which contains the shell script, then I have to add the path
to it. ./ means that it is in the current directory.

Creating the delete_backups.sh shell script

But after a while, a lot of backups will take up the desktop-backup
directory, and I probably would want to remove older backups. I can create
a separate script for that.

I could create another shell script to remove older backups:

#!/bin/bash

find /home/maria/desktop-backup/* -type f -mtime +1 -delete

The find command looks for files in a directory hierarchy. In the
script above, it is searching for the files located in
/home/maria/desktop-backup/, and the wildcard * means anything
(any file) inside /home/maria/desktop-backup/. -type f means of
type file. -mtime is interpreted as the number of whole days in the
age of a file. And -mtime +n (in this case +1) means greater than n
(whole) days. -delete deletes what is inside the
/home/maria/desktop-backup/ directory.

Adding the shell scripts to the crontab file

After I created these two shell scripts, I added them to my crontab
file.

First, I ran crontab -e in Terminal. It took me into the crontab file, where
I added my cron jobs. Then I added the following to the bottom of the
file below all the commented lines:

00 06 * * * /home/maria/Desktop/cron-job-scripts/desktop_backup.sh
05 06 * * * /home/maria/Desktop/cron-job-scripts/delete_backups.sh

The meaning of the first line is that the cron job will take place at
6am every day. The meaning of the second cron job is that it will
take place at 6:05am every day. The * in the day position which
follows the hour position, means every day. The next * to the right
is in the month position and means every month. And the last * (to the
right) which represents the day of the week, means every dayof the
week.

Since I just set up this cron job today, I will probably not reap its
benefits until the day after tomorrow. I will update this post with
the results when the contents of the desktop-backup is deleted!

Related Resources

The Cron daemon in Linux and how to create a cron job: mariadcampbell.com
How to Create and Set Up a Cron Job in Linux: phoenixNap
How To Format Date For Display or Use In a Shell Script: by Vivek Gite, cyberciti.biz

The lsblk command in Linux and what it does

Maria Campbell — Tue, 30 Jul 2024 15:28:38 +0000

Photo by Iker Urteaga on unsplash.com

This post was originally published on my personal blog mariadcampbell.com.

lsblk introduction
What is the lsblk command and what does it do?
Installing util-linux if your distro does not have it by default
lsblk syntax
Running the lsblk command
Footnotes
Related Resources

lsblk introduction

The lsblk command comes as part of the util-linux package, which is a
package comprised of essential utilities for Linux systems. It provides
a wide range of functionality including tools for managing files, disks,
and system resources. util-linux comes installed with Linux Mint, for
example. According to the Linux Mint community,

(util-linux) contains a number of important utilities, most of which are
oriented towards maintenance of your system. Some of the more important
utilities included in this package allow you to view kernel messages, create
new filesystems, view block device information, interface with real time
clock, etc.

What is the lsblk command and what does it do?

The lsblk command stands for list block devices, and it provides detailed
information about block devices such as hard drives, solid state drives,
and other storage related devices that are connected to the computer. It
queries the /sys virtual filesystem and
udev db [^1] to obtain the information that it displays.

Installing util-linux if your distro does not have it by default

If by any chance you are not using Linux Mint, or Ubuntu or an
Ubuntu derivate for example, and your Linux distro does not contain the
util-linux package, you can install it:

# Debian/Ubuntu
sudo apt-get install util-linux
# in Linux Mint, I have installed my packages doing sudo apt install packagename. But util-linus is already installed in Linux Mint anyway.

lsblk syntax

The syntax for the lsblk command is the following:

lsblk [options] [device]

[options] refers to the flags available to the lsblk command. [device]
refers to the specific block devices that we want to list. If no device
is specified, lsblk will list all block devices.

Running the lsblk command

If I run lsblk in Terminal, it returns the following:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda      8:0    0   50G  0 disk
├─sda1   8:1    0    1M  0 part
├─sda2   8:2    0  513M  0 part /boot/efi
└─sda3   8:3    0 49.5G  0 part /
sr0     11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

If I want to get all block devices including empty ones, I would run the
following:

lsblk -a

Which for me returns:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0    0B  0 loop
loop1    7:1    0    0B  0 loop
loop2    7:2    0    0B  0 loop
loop3    7:3    0    0B  0 loop
loop4    7:4    0    0B  0 loop
loop5    7:5    0    0B  0 loop
loop6    7:6    0    0B  0 loop
loop7    7:7    0    0B  0 loop
sda      8:0    0   50G  0 disk
├─sda1   8:1    0    1M  0 part
├─sda2   8:2    0  513M  0 part /boot/efi
└─sda3   8:3    0 49.5G  0 part /
sr0     11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

If I want to print out the information in list format, I would run the
following:

lsblk -l

Which for me returns:

NAME MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda    8:0    0   50G  0 disk
sda1   8:1    0    1M  0 part
sda2   8:2    0  513M  0 part /boot/efi
sda3   8:3    0 49.5G  0 part /
sr0   11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

Now devices are listed without showing which ones are related to
each other like with the lsblk command.

If I run the following command in Terminal:

lsblk -p

For me, it returns the following:

NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
/dev/sda      8:0    0   50G  0 disk
├─/dev/sda1   8:1    0    1M  0 part
├─/dev/sda2   8:2    0  513M  0 part /boot/efi
└─/dev/sda3   8:3    0 49.5G  0 part /
/dev/sr0     11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

The -p flag produces output in key value pairs. The big difference here
is the absolute path to the device as well as the relationships between
related devices is also displayed. To learn more about lsblk, run
man lsblk in Terminal.

Footnotes

[^1]: udev (db) or
user /dev is systemd's device manager for the Linux kernel. It manages device
nodes in /dev and handles all user space actions when adding or removing
devices.

According to man udev, udev supplies the system software with device events,
manages permissions of device nodes and may create additional symlinks in the
/dev/ directory, or renames network interfaces. The kernel usually just assigns
unpredictable device names based on the order of discovery. Meaningful symlinks
or network device names provide a way to reliably identify devices based on
their properties or current configuration.

The udev daemon,
systemd-udevd.service(8),
receives device uevents directly from the kernel whenever a device is added or
removed from the system, or it changes its state. When udev receives a device
event, it matches its configured set of rules against various device attributes
to identify the device. Rules that match may provide additional device
information to be stored in the udev database or to be used to create meaningful
symlink names.

All device information udev processes is stored in the udev database and sent
out to possible event subscribers. Access to all stored data and the event
sources is provided by the library libudev.

Related Resources

The Linux Filesystem Hierarchy: mariadcampbell.com
How to List All Block Devices in Linux | lsblk Command: Geeks for Geeks

The script command in Linux and Unix (macOS)

Maria Campbell — Sun, 28 Jul 2024 09:38:00 +0000

Photo by Pixabay on pexels.com

This post was originally published on my personal blog mariadcampbell.com.

In my article The pipe (|) and tee commands in Linux and Unix (macOS),
I talk about how one can save the stdout resulting from a command using pipe
(|) and tee. In this article, I discuss the Linux script command. The
script command records all Terminal activity.

Running the (default) script command in Linux and Unix (macOS)

When I run the script command by typing "script" in Terminal followed by
the Return (Enter) key, the following is returned in Terminal in both
Linux and Unix (macOS):

Script started, output log file is 'typescript'

And if I run ls on the home directory (~), the typescript file appears in
my current working directory. When I run the script command without any
args, a file called typescript is automatically created by default.
This file saves all Terminal related activity information in the
current Terminal session.

For example, if I open up the typescript file with the vim command in
Linux, it looks something like the following:

Script started on 2024-07-14 19:29:11-04:00 {TERM="xterm-256color" TTY="dev/pts/2" COLUMNS="80" LINES="24"]
^[[?2004h^[]0;maria@maria-VirtualBox: ~^G^[01;32mmaria@maria-VirtualBox^[[00m:^[[01;34m~^[[00m$ ls^M
^[[?2004l^M^[[0m^[[01;34mDesktop^[[00m  ^[[01;34mDownloads^[[00m  ^[[01;34mPictures^[[00m ^[[01;34mTemplates^[[00m  ^[[01;34mVideos^]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]...
[[5;3H^[[30m^[[47m| Please select the mail server configuration type that best meets your   ^[[97m^[[40m ^[[6;3H^[[30m^[[47m| needs.[[97m^[[40m ^[[7;3H^[[30m^[[47m|
                                              ^[[97m
                                        1872,643-553  Bot

It is a long file, and I was not able to export the typescript file from
Linux Mint in VirtualBox into Windows 11. If anyone knows of a way of
doing that, let me know! I tried to install a an email server package, but
couldn't get beyond the configuration step. I couldn't configure it in
Terminal and couldn't exit the package configuration either.

It is basically the same process to start the script command in Unix
(macOS).

Let's say I just run the script command without any args from inside
mariadcampbell.com's local repository directory:

script

This resulted in the following:

mariacam@Marias-MBP  ~/Development/nextjs-and-react-complete-guide/fullstack-blog   main  script

Script started, output file is typescript

And a file called "typescript" was created inside this directory:

ls

# the following was returned:

?[38                                    jest.config.js
?[?1049l?[?25h?[                        jest.setup.js
?[?2004l??                              lib
4                                       list-directory.txt?[39m?[36D?[39m
LICENSE                                 list-directory.txt?[39m?[36D?[39m-?[39m
README.md                               list-directory.txt?[39m?[36D?[39m=?[39m
__mocks__                               next.config.js
__tests__                               node_modules
c?[38                                   package-lock.json
c?]10                                   package.json
certificates                            pages
components                              postcss.config.js
coverage                                public
data                                    scripts
demo.txt                                started
done,                                   started,
exit                                    styles
fullstack-blog-script                   tailwind.config.js
helpers                                 typescript
hooks

The stdout of typescript looked like the following:

Script started on Mon Jul 15 12:25:21 2024
[1G[0K[1G[0K/Users/mariacam/.zshrc:110: command not found: pyenv
]1337;RemoteHost=mariacam@Marias-MBP]1337;CurrentDir=/Users/mariacam/Development/nextjs-and-react-complete-guide/fullstack-blog]1337;ShellIntegrationVersion=11;shell=zsh/Users/mariacam/.zshrc:114: command not found: pyenv
[1m[7m%[27m[1m[0m

]2;mariacam@Marias-MBP: ~/Development/nextjs-and-react-complete-guide/fullstack-blog]1;..ullstack-blog]133;D;0]1337;RemoteHost=mariacam@Marias-MBP]1337;CurrentDir=/Users/mariacam/Development/nextjs-and-react-complete-guide/fullstack-blog
[0m[27m[24m[J]133;A[39m[0m[49m[40m[39m mariacam@Marias-MBP [44m[30m[30m ~/Development/nextjs-and-react-complete-guide/fullstack-blog [43m[34m[30m  main [49m[33m[39m ]133;B[K[?1h=[?2004hll[90ms[39ml[39ms[?1l>[?2004l

]2;ls -G]1;ls]133;C;?[38                                    jest.config.js
?[?1049l?[?25h?[                        jest.setup.js
?[?2004l??                              [1m[36mlib[39;49m[0m
4                                       list-directory.txt?[39m?[36D?[39m
LICENSE                                 list-directory.txt?[39m?[36D?[39m-?[39m
README.md                               list-directory.txt?[39m?[36D?[39m=?[39m
[1m[36m__mocks__[39;49m[0m                               next.config.js
[1m[36m__tests__[39;49m[0m                               [1m[36mnode_modules[39;49m[0m
c?[38                                   package-lock.json
c?]10                                   package.json
[1m[36mcertificates[39;49m[0m                            [1m[36mpages[39;49m[0m
[1m[36mcomponents[39;49m[0m                              postcss.config.js
[1m[36mcoverage[39;49m[0m                                [1m[36mpublic[39;49m[0m
[1m[36mdata[39;49m[0m                                    [1m[36mscripts[39;49m[0m
demo.txt                                started
done,                                   started,
exit                                    [1m[36mstyles[39;49m[0m
[31mfullstack-blog-script[39;49m[0m                   tailwind.config.js
[1m[36mhelpers[39;49m[0m                                 typescript
[1m[36mhooks[39;49m[0m
[1m[7m%[27m[1m[0m

]2;mariacam@Marias-MBP: ~/Development/nextjs-and-react-complete-guide/fullstack-blog]1;..ullstack-blog]133;D;0]1337;RemoteHost=mariacam@Marias-MBP]1337;CurrentDir=/Users/mariacam/Development/nextjs-and-react-complete-guide/fullstack-blog
[0m[27m[24m[J]133;A[39m[0m[49m[40m[39m mariacam@Marias-MBP [44m[30m[30m ~/Development/nextjs-and-react-complete-guide/fullstack-blog [43m[34m[30m  main [49m[33m[39m ]133;B[K[?1h=[?2004h 90mc -l fullstack-blog-scr[90mi[90mpt[39m[K[A[93Cw[39mc[39m [39m-[39ml[39m [39mt[K[1B
[K[A[102Cypescript[?1l>[?2004l[1B

If I wanted to find out how many lines typescript contains, I ran the
following command:

wc -l typescript

which returns:

24 typescript

This means that the file contains 24 lines. And if I run the exit command,
the following is returned:

Script done, output file is typescript

And if I then run wc -l typescript again, it returns the following:

28 typescript

That is because the exit command is appended to the end of the
typescript file.

]2;wc -l typescript]1;wc]133;C;      24 typescript
[1m[7m%[27m[1m[0m

]2;mariacam@Marias-MBP: ~/Development/nextjs-and-react-complete-guide/fullstack-blog]1;..ullstack-blog]133;D;0]1337;RemoteHost=mariacam@Marias-MBP]1337;CurrentDir=/Users/mariacam/Development/nextjs-and-react-complete-guide/fullstack-blog
[0m[27m[24m[J]133;A[39m[0m[49m[40m[39m mariacam@Marias-MBP [44m[30m[30m ~/Development/nextjs-and-react-complete-guide/fullstack-blog [43m[34m[30m  main [49m[33m[39m ]133;B[K[?1h=[?2004hee[90mxit[39me[39mx[39mi[39mt[?1l>[?2004l

]2;exit]1;exit]133;C;
Script done on Mon Jul 15 12:29:28 2024

Running custom scripts in Unix (macOS)

Now let's say I want to do things a bit differently, follow a different script
(other than script itself) inside my fullstack-blog directory which houses
the local repo for mariadcampbell.com:

npm run dev 2>&1 | tee ~/desktop/full-stack-blog.txt

Instead of using the script command, I am using a "custom script". In
fact, it is an npm local script located in my package.json file for
mariadcampbell.com. The following then is returned in Terminal:

 fullstack-blog@0.1.0 dev
> next dev

  ▲ Next.js 14.2.4
  - Local:        http://localhost:3000
  - Environments: .env.development.local, .env.local, .env

 ✓ Starting...
 ✓ Ready in 1241ms

The custom script resulted in first running the npm run dev command
and starting up the development server for fullstack-blog in the
browser, and the stdout to Terminal is the following above. But since I
also use pipe | and tee, it resulted in the creation of a file
called fullstack-blog.txt on the desktop, and it contained the
following:


> fullstack-blog@0.1.0 dev
> next dev

  ▲ Next.js 14.2.4
  - Local:        http://localhost:3000
  - Environments: .env.development.local, .env.local, .env

 ✓ Starting...
 ✓ Ready in 1241ms

which is the same as stdout to Terminal!

In addition, I am redirecting any errors that may occur to
fullstack-blog.txt as well. 2 points to stderr. 1 points to stdout.
And 2>&1 redirects npm run dev stdout and stderr to
fullstack-blog.txt. Specifically, 2>&1 means redirect stderr to
stdout, and both are stdin for the tee command, which basically copies
and pastes stdout to a specified file. In this case, fullstack-blog.txt.

Let's say I wanted to stop npm run dev, thereby stop redirecting it to
the fullstack-blog.txt file. I simply press the Control key + C key like I
would normally when I want to stop running the development server. But if
I simply ran npm run dev afterwards, the stdout to Terminal would no
longer be redirected to fullstack-blog.txt. I would have to re-run
npm run dev 2>&1 | tee ~/desktop/full-stack-blog.txt. And if I want to
append new stdout to the end of the file instead of overwriting it,
the default behavior of the tee command, I would run the following
instead:

npm run dev 2>&1 | tee -a ~/desktop/full-stack-blog.txt

And now the stdout of fullstack-blog.txt is the following:

> fullstack-blog@0.1.0 dev
> next dev

  ▲ Next.js 14.2.4
  - Local:        http://localhost:3000
  - Environments: .env.development.local, .env.local, .env

 ✓ Starting...
 ✓ Ready in 1241ms

> fullstack-blog@0.1.0 dev
> next dev

  ▲ Next.js 14.2.4
  - Local:        http://localhost:3000
  - Environments: .env.development.local, .env.local, .env

 ✓ Starting...
 ✓ Ready in 1154ms

The same can be done with any script that you want to save to a file.
This way, if you want to be able to refer back to the
logging information and find out what went wrong, for example, or
perhaps what went right, you could refer to the .txt file that the
stdout was redirected to, written to, and saved. For
nextjs developers, for example, or developers in general, doing this
with the build script, the production server post-build, the
test script, any linting scripts, etc., is very useful.

If I make my way around my nextjs application in the browser, this is
logged as well. I visited a couple of pages and posts, and since I was using
the -a or --append flag, the new stdout was added to the end of the
fullstack-blog.txt file:

> fullstack-blog@0.1.0 dev
> next dev

  ▲ Next.js 14.2.4
  - Local:        http://localhost:3000
  - Environments: .env.development.local, .env.local, .env

 ✓ Starting...
 ✓ Ready in 1241ms

> fullstack-blog@0.1.0 dev
> next dev

  ▲ Next.js 14.2.4
  - Local:        http://localhost:3000
  - Environments: .env.development.local, .env.local, .env

 ✓ Starting...
 ✓ Ready in 1154ms
 ○ Compiling / ...
 ✓ Compiled / in 618ms (816 modules)
Warning: data for page "/" is 132 kB which exceeds the threshold of 128 kB, this amount of data can reduce performance.
See more info here: https://nextjs.org/docs/messages/large-page-data
 GET / 200 in 926ms
 ✓ Compiled /about in 185ms (823 modules)
 ✓ Compiled /blog in 163ms (839 modules)
Warning: data for page "/blog" is 1.28 MB which exceeds the threshold of 128 kB, this amount of data can reduce performance.
See more info here: https://nextjs.org/docs/messages/large-page-data
 GET /_next/data/development/blog.json 200 in 104ms
 ✓ Compiled /_error in 71ms (841 modules)
 GET /images/blog/the-script-command-in-linux-and-unix-macos/undefined 404 in 103ms
 ⨯ The requested resource isn't a valid image for /images/blog/the-script-command-in-linux-and-unix-macos/undefined received text/html; charset=utf-8
Warning: data for page "/" is 132 kB which exceeds the threshold of 128 kB, this amount of data can reduce performance.
See more info here: https://nextjs.org/docs/messages/large-page-data
 GET /_next/data/development/index.json 200 in 51ms
 ○ Compiling /blog/[slug] ...
 ✓ Compiled /blog/[slug] in 644ms (1644 modules)
 GET /_next/data/development/blog/using-pipe-and-grep-in-linux-and-unix-macos.json?slug=using-pipe-and-grep-in-linux-and-unix-macos 200 in 1036ms
Warning: data for page "/blog" is 1.28 MB which exceeds the threshold of 128 kB, this amount of data can reduce performance.
See more info here: https://nextjs.org/docs/messages/large-page-data
 GET /_next/data/development/blog.json 200 in 143ms
 GET /images/blog/the-script-command-in-linux-and-unix-macos/undefined 404 in 7ms
 ⨯ The requested resource isn't a valid image for /images/blog/the-script-command-in-linux-and-unix-macos/undefined received text/html; charset=utf-8
 GET /_next/data/development/blog/the-script-command-in-linux-and-unix-macos.json?slug=the-script-command-in-linux-and-unix-macos 200 in 16ms

This is much longer than the previous stdout I shared here!

Related Resources

How to Save Terminal Output to a File for Future Reference:
mariadcampbell.com
script command in Linux with Examples:
Geeks for Geeks

Some Important Terms to Know in Linux

Maria Campbell — Sun, 28 Jul 2024 09:31:00 +0000

Photo by Karolina Kaboompics on pexels.com

This post was originally published on my personal blog mariadcampbell.com.

In order to be able to understand what Linux is all about, there are certain
Linux terms you should become familiar with from the get go.

The Linux kernel

First an foremost, you should know what is meant by the
Linux Kernel.

The Linux® kernel is the main component of a Linux operating system (OS)
and is the core interface between a computer’s hardware and its
processes. It communicates between the 2, managing resources as efficiently
as possible.

The kernel is so named because—like a seed inside a hard shell—it exists
within the OS and controls all the major functions of the hardware, whether
it’s a phone, laptop, server, or any other kind of computer. -- What is the
Linux kernel?,
RedHat

The Linux kernel accomplishes 4 tasks:

Memory management: keeps track of how much memory is used to store what and where
Process management: determines which processes can use the central processing unit (CPU), and for how long.
Device drivers: acts as a mediator/interpreter between the hardware and the processes.
System calls and security: receives requests for service from processes.

The kernel works invisibly in the kernel space, where it
allocates memory and keeps track of where everything is stored. The
user sees things like web browsers and files, and these live in the
user space. These applications interact with the kernel via a
system call interface (SCI).

GNU

GNU, or "GNU's Not Unix", is a collection of open source tools that
anyone can use for free to develop their own apps and
operating systems.

The GNU Project, founded by Richard Stallman, develops and
distributes software for free and provides every developer with
open-source tools to do the same.

The Linux kernel is licensed under GNU's GPL (General Public License)
and is known as GNU/Linux. Any operating system developed using
open-source GNU tools and the Linux kernel falls under the category
of Linux distributions.

Linux distribution

A Linux distribution (or distro) is an operating system (OS) compiled
from components developed by open source projects/programmers.

Each distribution includes:

the Linux kernel (the core of the OS),
GNU (GNU's Not Unix) shell utilities (terminal interface and commands),
the X server (a graphical desktop),
the desktop environment,
package management system,
an installer,
other services

Distributions also include an internet browser, management tools, and
other software such as the KVM (Kernel-based Virtual Machine) hypervisor
[^1]. A single Linux distribution may contain thousands of
software packages, utilities, and applications.

Linux package managers

Package managers are programs that manage packages on a Linux system. It
allows us to add or delete packages from sources such as our distribution's
repositories or third party repositories.

APT, RPM, and pacman are the three most popular package managers
used by Linux distributions. Debian and Ubuntu-based distributions
use the APT package manager. Fedora, CentOS, and RHEL have the RPM
package manager. Arch Linux and its derivatives ship with pacman.

Source and binary packages

A Linux package is a compressed software archive file containing all the
files comprising a software application that provides a
particular functionality.

Linux software ere usually distributed as packages, and there are
two types of packages available: source and binary.

Source packages contain program source code that a user has to manually
compile and install in order to run the software.

Binary packages contain pre-built and pre-compiled executables for the
software.

Linux repositories

Software repositories are remote servers that store a collection of
packages along with related metadata [^3]. Every
Linux distribution either has its own repositories or uses
repositories of its parent distribution to provide software to the
users.

Linux Boot loader

A boot loader is is program which loads the OS into RAM during the
boot process [^2]. The boot loader helps load the correct
operating system during boot time and adds initial processes into
memory (RAM).

Linux services

A Linux service
(cron daemon is a
service) is a process or application that runs in the background, either
doing some predefined task or waiting for some event. systemd, which is
a system and service manager for Linux, is the first process to run in
the system.

Linux filesystem

At a high level, the Linux filesystem follows the
Filesystem Hierarchy Standard (FHS). This standard describes the
common layout conventions used by most UNIX and UNIX-like systems. It
consists of a single primary or root directory with multiple branching
sub-directories.

/ represents the root of the Linux filesystem. It is under this
root directory that all other files and directories reside. The
Filesystem Hierarchy Standard
(FHS) describes the different directories and what files are located
in which directories.

If you have Ubuntu or a Ubuntu derivative installed (like Linux Mint for
example), you can install a package called tree by running the
following command in Terminal:

# to update current packages. updates the list of available packages and their versions, but it does not install or upgrade any packages.
sudo apt update
# actually installs newer versions of the packages you have. After updating the lists, the package manager knows about available updates for the software you have installed. This is why you first want to update.
sudo apt upgrade
# now you are ready to install tree
sudo apt install tree

Now you can run a command like the following:

tree /

The tree command lists contents of directories in a tree-like format in
Linux. With no args, it lists the files and sub-directories in
the current directory. With directory args (such as / or ~), tree
lists all the files and/or directories found in the
given directories. When completing the list of all files and
directories found, tree returns the total number of files and/or
directories listed.

If you want a short list of files and directories in root (/), for
example, you can run something like the following instead:

# run from root directory `/`
tree -L 1 /

What this command essentially is doing is it shows only the first level
of the directory tree starting at root (/). The -L option tells
tree how many levels down we want to see. Here, we indicate
1 level.

Types of files in Linux

In Linux and Unix systems, everything is considered a file. If it
isn't, it's a running process. Basically, files fall under three different
categories in Linux:

Regular files: these include text files, photos, videos, programs, and executable files.
Directories: in Linux, directories are also considered files since they provide storage for other files and sub-directories.
Special files: device files that are made up of symbolic links, block files, socket files, and named pipe files.

I will discuss the Linux Filesystem Tree in greater detail in an upcoming
article. It's too lengthy to include here.

root directory vs root user

The root (/) directory, mentioned previously, represents the root of
the Linux filesystem. It is under this root directory that all other
files and directories reside.

The root user, or superuser, or just root, is the user that has all
administrative privileges. The root user can read, write/edit, and
delete any file, make changes to the system or other users, and even
delete the whole directory tree. root is the Linux user with the
highest level of control. To learn a bit more about root and related
sudo, sudo su, and su commands, please visit my article
The su command in Linux and Unix (macOS).

X Window System

The X Window System
provides the base technology for developing graphical user interfaces.

Linux desktop environment

A Linux desktop environment bundles together various components to provide
common graphical user interface elements such as icons, toolbars,
wallpapers, and desktop widgets. And most desktop environments include a
set of integrated applications and utilities. It is the
desktop environment that permits us to use Linux graphically using a
mouse and keyboard like we do in other OS like Windows or macOS.

Linux Command Line Interface

The Linux Command Line Interface (also available in other OS like Windows
and macOS) is what we use to interact with a computer's OS using the
computer keyboard. We can enter text commands to navigate,
run programs, or configure our computer system. All operating systems
(OS), including Windows, Linux and macOS, provide a CLI in
addition to a graphical user interface (GUI).

Oftentimes Terminal, Command Line, Console, or Shell are used
interchangeably. However, they are not all exactly the same.

A "Terminal" is a text input/output (I/O) environment.

A Terminal window, aka Terminal emulator, is a text only window that
emulates a user's Console in a Graphical User Interface (GUI).

A Terminal is a program that allows us to run a shell. It is a
device with a human readable display that accepts a stream of
characters and displays them. They are used frequently in networking and
device debugging interfaces.

A Console is a physical Terminal. It is an instrument panel with
computer controls. It is a type of terminal, and is a window which
contains active text-mode programs. The Console recognizes
key presses (stdin) and is aware of its width and height.
Full screen mode is available.

A Shell is a command line interpreter. It processes commands (stdin) and
outputs the results (stdout). A Shell is a layer that sits on top
of the kernel:

It interprets and processes the commands entered by the user. Users don't have access to the kernel, but the shell does. Users can only gain access to the kernel by using a shell and entering commands or running programs.
System calls are used by programs to gain access to the kernel's functionality.

The Command Line is an area to the right of the command prompt in the
Terminal window where a user enters commands and data. This is
the line where we type our commands.

Linux Shells

Linux shells can be either be a command line interpreter like Terminal
or a graphical interpreter like GNOME Shell. We can also install
different shells in Linux. Examples include Bash, Zsh,
Fish, sh, and Ksh.

The following are two ways one can list the shells currently available
in one's Linux distribution:

Using the cat command:

cat /etc/shells
# which returns:
# /etc/shells: valid login shells
/bin/sh
/bin/Bash
/usr/bin/bash
/bin/rbash
/usr/bin/rbash
/usr/bin/sh
/bin/dash
/usr/bin/dash

Using grep:

grep -v '^#' /etc/shells
# which returns the same as with cat command except for the message:
/bin/sh
/bin/Bash
/usr/bin/bash
/bin/rbash
/usr/bin/rbash
/usr/bin/sh
/bin/dash
/usr/bin/dash

cat /etc/shells displays the contents of /etx/shells.

grep -v '^#' /etc/shells allows to filter and display only the lines
that contain valid shell entries. The regular expression ^ character
means beginning of the line, and # means to search for lines
that begin with #. But the -v flag, or --invert-match, means to select
non-matching lines, so lines that don't begin with #, which
would represent a comment. That is why the comment
# /etc/shells: valid login shells does not appear here.

Linux shell scripting

Shell scripting (not just in Linux) refers to the process of
writing scripts using (Linux) commands, which are then interpreted
by the shell installed in Linux. Batch scripts in Windows are the
equivalent to shell scripts in Linux.

The most popular form of shell scripting in Linux is Bash scripting,
which means writing and executing scripts using the Bash shell.
Shell scripts are used to automate tasks and are added to
crontab files as cron jobs. To learn how to set up a basic cron job
using the Cron daemon, please visit my article entitled
The Cron daemon in Linux and how to create a cron job.
I will be adding more articles regarding creating different cron jobs in
the near future.

Footnotes

[^1]: a
hypervisor is a
program that separates a computer's OS and applications from the underlying
physical hardware. This is what enables virtualization and cloud computing
solutions for modern IT infrastructures.

A hypervisor allows the physical host machine to operate multiple virtual
machines (VMs like VirtualBox, for example) as guests. This increases the
effectiveness of computing resources such as memory, network bandwidth, disk
space and CPU cycles.

VMs can run on the same physical hardware, but they are logically separated from
each other, preventing a failure in one VM from affecting other VMs on the same
physical machine.

A hypervisor creates, runs, and manages virtual machines.

[^2]: The boot process is the process of loading an OS. It starts when we
turn on a computer and ends when the OS is loaded into memory.

[^3]: Linux package metadata describes a package for its consumers: who
wrote it, where its repository is, and what versions of it have been published.
It also contains a description of each version of a package present in the
registry, listing its dependencies, giving the url of its tarball, etc.

Related Resources

How to Install and Use Popular Linux Bootloaders:
baeldung.com
Computer Boot Process Explained:
baeldung.com
The Linux Filesystem:
by perfectogo, medium.com
Classic SysAdmin: The Linux Filesystem Explained:
The Linux Foundation
Linux command line for you and me!¶:
LYM
Difference between Terminal, Console, Shell, and Command Line:
Geeks for Geeks
15 Linux Terms, Jargons, and Lingo You Should Know About:_
makeuseof_

DEV Community: Maria Campbell

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Copying an application from one Django project into another

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Configuring the polls app in cast-votes

Conclusion

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Table of Contents

So why this article?

What does Vim stand for?

Configuring Vim

The vim command

Vim modes

Normal mode

The (lowercase) gg shortcut

The (uppercase) G shortcut

The # (number) G shortcut

The (lowercase) h shortcut

The (lowercase) j shortcut

The (lowercase) k shortcut

The (lowercase) l shortcut

The # (number) j shortcut

The # (number) k shortcut

The (lowercase) w shortcut

The (lowercase) b shortcut

The (lowercase) e shortcut

The (uppercase) W shortcut

The (uppercase) B shortcut

The (uppercase) E shortcut

The 0 (zero) shortcut

The ^ (caret) shortcut

The (dollar sign) $ shortcut

The (lowercase) r shortcut

The (lowercase) x shortcut

The (uppercase) X shortcut

The (lowercase) dw shortcut

The (lowercase) cw shortcut

The (lowercase) s shortcut

The (uppercase) S shortcut

The (uppercase) D shortcut

The (lowercase) dd shortcut

The (uppercase) C shortcut

The (lowercase) yy shortcut

The (lowercase) p shortcut

The (uppercase) P shortcut

The (lowercase) u shortcut

The Control + r shortcut

Repeating commands

Repeating a command using a count

Insert mode

Entering Insert mode