DEV Community: Mohammad Moallemi

How to accept command line arguments in Node.js scripts?

Mohammad Moallemi — Sun, 02 May 2021 20:34:35 +0000

How to accept command line arguments in Node.js scripts?

In this short blog post, we’re going to see how we can write a Node.js script that accepts command line arguments and named arguments.

As we know in any Node.js script we have an object called process which contains a lot of information about the current running process from environment variables to PID and etc...

One of the available keys in process object is argv and we can easily access it via process.argv.

The two first items are Node.js executable path and JavaScript file path followed by provided command-line arguments unless you run it in an interactive Node.js shell.

// From script file named main.js  
console.log(process.argv)  
[ '/usr/bin/node', '/home/mmoallemi/main.js' ]  

// From interactive node  
❯ node  
Welcome to Node.js v15.14.0.  
Type ".help" for more information.  
> process.argv  
[ '/usr/bin/node' ]

We should use process.argv.slice(2) instead:

node main.js first second third  

~   
❯ node main.js  first second third  
[  
  'first',  
  'second',  
  'third'  
]

Great! So far we have achieved to pass positional arguments to our script but if we want to use named arguments or some kind of flags?

node main.js extract --input=test.txt --output=results.txt  
[  
  'extract',  
  '--input=test.txt',  
  '--output=results.txt'  
]

We passed one positional argument and two named arguments, we can go ahead and clean the values and split them by = and this kind of stuff, but let's do it right.

Install minimist using your favorite package manager, I use yarn:

yarn add minimist

and then pass arguments to minimist to parse it:

// node main.js extract --input=test.txt --output=results.txt  
// main.js script  
const minimist = require('minimist')  

const args = process.argv.slice(2)  

const parsedArgs = minimist(args)  

console.log('Parsed Arguments:', parsedArgs)  

console.log('Input:', parsedArgs.input)  
console.log('Output:', parsedArgs.output)  

console.table(parsedArgs)

Enjoy the results!

Parsed Arguments: { _: [ 'extract' ], input: 'test.txt', output: 'results.txt' }  

Input: test.txt  
Output: results.txt  

┌─────────┬───────────┬───────────────┐  
│ (index) │     ۰     │    Values     │  
├─────────┼───────────┼───────────────┤  
│    _    │ 'extract' │               │  
│  input  │           │  'test.txt'   │  
│ output  │           │ 'results.txt' │  
└─────────┴───────────┴───────────────┘

Happy scripting!

Originally published at https://mmoallemi99.com on May 2, 2021.

How to auto mount NVMe EBS Volumes on EC2?

Mohammad Moallemi — Thu, 29 Apr 2021 08:38:01 +0000

Image used from AWS youtube channel: https://www.youtube.com/watch?v=77qLAl-lRpo

In this tutorial, we’re going to mount an NVMe EBS volume to an EC2 instance and add it to /etc/fstab so it automatically mounts the volume after reboots.

First list block devices using lsblk:
sudo lsblk

You will see a result similar to this:

List block devices in order to see all available NVMe devices

The NVMe volumes names follow the pattern below:

/dev/nvme0n1
/dev/nvme1n1
/dev/nvme2n1
.
.
.
/dev/nvme\[0-26\]n1

Then build a Linux file system of your choice, I picked ext4 here:

sudo mkfs -t ext4 /dev/nvme1n1

Verify the build using the file command and copy the UUID value:

sudo file -s /dev/nvme1n1

The result is something like this:

/dev/nvme1n1: Linux rev 1.0 ext4 filesystem data, UUID=

Now edit /etc/fstab with the editor of your choice (I prefer nano xD) and add the following line to it:

UUID="<copied-uuid-value>" <mount-directory-path> ext4 defaults 0 0

Now we use the mount utility to verify and mount the volume.

sudo mount -a

You can checkout your mounted volumes using:

The result is something like this:

Getting a report of mounted file systems and disk space usage

I hope you enjoyed it, feel free to drop a comment if you have any questions.

Happy Engineering!

Originally published at https://mmoallemi99.com on April 28, 2021.

Serverless Micro Django | Lightweight, yet powerful Python utility for lambda functions

Mohammad Moallemi — Thu, 25 Feb 2021 16:05:25 +0000

https://github.com/mmoallemi99/serverless-micro-django/

A couple of weeks ago I had this task in agileful to refactor and improve some AWS lambda functions.

There was a bunch of pure SQL queries written alongside python codes which made me think, what if we could use standalone Django ORM in our python lambda functions?

So I did some digging on how we can use my beloved ORM in python scripts despite the serverless stuff, there were some vague and old answers but I managed to make something out of it.
It’s as simple as defining a database connection settings and calling django.setup().

Standalone Django ORM

Here is the minimal python code needed to use standalone Django ORM:

handler.py

serverless_micro_django/settings.py

Plus these two files you need to create your desired Django app models. (e.g. videos_app/models.py)

There is one downside in this way of using Django and that is the lack of manage.py!
I haven’t got time to try adding manage.py commands so I added some helper scripts like the ones below:

makemigrations.py / migrate.py

So even if you just need Django ORM without all the serverless and fancy stuff use the codes above and you’re good to go. Or check out the GitHub repository:
https://github.com/mmoallemi99/serverless-micro -django

Serverless Micro Django!

So let’s make it Serverless!
As we know lambda functions must accept two function parameters: event, context.

As SMD (Serverless Micro Django) is supposed to be lightweight and micro! it doesn’t support any REST API like Django & Flask. Just function!

Hence when you are invoking the function you must pass your desired action/event in lambda event argument:

test_lambda.py

And in the end, I developed a ModelController so I can execute the events. Which I’m not going to get into and talk about.

I’ve also done some event input validations and modeling using PyDantic which you can find in the project’s GitHub repository.

I know there is a long way for SMD to become mature and production-ready. I would gladly accept and be open to contributions and feedback. (Documenting, Development, Content Writing, etc…)

GitHub Repository:
https://github.com/mmoallemi99/serverless-micro-django

Originally published at https://mmoallemi99.com

How to upgrade to Python 3.9.0 on Ubuntu 18.04 LTS without internal bleeding!

Mohammad Moallemi — Thu, 25 Feb 2021 15:45:04 +0000

SPOILER ALERT:
Upgrading the Python version on Ubuntu breaks some packages like apt and pip in your system!
[Bleeding SysAdmin crawling]

In this article we’re going to upgrade python and fix the issues.

Start reading this article and executing the instruction:
How to upgrade to Python 3.9.0 on Ubuntu 18.04 LTS
It will guide you through updating the repo and basic updating stuff.

After that, try running sudo apt update.
See!

ModuleNotFoundError: No module named ‘apt_pkg’

or event a simple pip3 install virtualenv:

ImportError: cannot import name ‘sysconfig’ from ‘distutils’ (/usr/lib/python3.9/distutils/init.py)

Well, that’s a lot of errors!
BUT:
This is GNU/Linux bruh! We always have solutions! [D’Oh!]

At first, you need to resync old python packages to new corresponding paths, we’ll first navigate to python3 dist-packages folder and use ln command to make links.

Linking old python packages to new ones

If you consider your old python version 3.6 and the new one 3.9 the ln command would be something like above: (change 36 and 39 numbers accordingly)

Then uninstall any existing python-apt packages using two apt purge commands and reinstall them just like a normal apt package

Reinstalling python-apt package

BEWARE: using apt with --reinstall flag doesn't work!
Now run sudo apt update.

YaY! It’s fixed! [Mic Drop!]

But wait a second, I still can’t install pip packages!
Just run this command and you’ll be good to go:
sudo apt install python3.9-distutils python3.9-dev

Happy SysAdminning!

Thanks to the free software community for this beautiful world we’re living in!

Sources:
How to upgrade to Python 3.9.0 on Ubuntu 18.04 LTS
StackOverFlow: python-dev installation error: ImportError: No module named apt_pkg
AskUbuntu: ImportError: cannot import name ‘sysconfig’ from ‘distutils’ (/usr/lib/python3.9/distutils/init.py)

https://stackoverflow.com/questions/13708180/python-dev-installation-error-importerror-no-module-named-apt-pkg

Originally published at https://mmoallemi99.com on February 17, 2021.

How to get a job as a Python/Django backend developer roadmap

Mohammad Moallemi — Tue, 06 Oct 2020 18:43:26 +0000

A while ago I designed a Django Developer Career Roadmap for those who wish to start in this field and enter the software industry market.

I’ve recently created a GitHub repository and updated it with some new stuff.
Check out the repository if you wish to become a Django developer or strive to improve your existing skills!
https://github.com/mmoallemi99/developer-career-roadmap/

p.s. this roadmap assumes you have knowledge in python and programming fundamentals

If you have any suggestion or you wish to improve the roadmap, feel free to open a pull request in GitHub!

Happy coding 🙂

Source:
https://mmoallemi99.com/blog/how-to-get-a-job-as-a-python-django-backend-developer-roadmap/