Nicolas Baptista

Use Crontab for automating recurring tasks on Fedora/CentOS

04/08/2021 Nicolas Baptista Fedora/CentOS/RedHat, Server Maintenance 0 Comments

You can use a tool that is called “Crontab” for recurring tasks automation. It is available for all the Linux systems and still the most used solution.

Edit the crontab configuration file

crontab -e

This will open vi, the default linux editor, that will allow you to edit the recurring tasks for a specific date and time. 

# Example of job definition:
# .---------------- minute (0 - 59)
# |  .------------- hour (0 - 23)
# |  |  .---------- day of month (1 - 31)
# |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# |  |  |  |  |
# *  *  *  *  *  user command to be executed

In vi the main commands used are:
– The escape key (:x! to save OR :q! to quit)
– a to append text
– i to insert text
– dd to remove the line
– x to delete the current selected character

Verify the date and time zone

You can verify the date and the time zone (most of the cloud machines are using the UTC time zone). you can use the following command “date”:

# date
Wed Aug  4 01:10:10 UTC 2021

Sort your result by distance – Node.JS

01/08/2021 Nicolas Baptista Javascript, JSON, Node.JS, REST API 0 Comments

Supposed that you return in your Node.JS backend a list of items, and you want to sort the results by distance.

For exemple, you do a GET /usersLocation and you have it:

[
   {
      name: "Paul",
      gender: "man",
      distance: 4.1
   },
   {
      name: "Philip",
      gender: "man",
      distance: 4.9
   },
   {
      name: "Elina",
      gender: "woman",
      distance: 2.5
   }
]

In your app you have the result to be listed by distance for exemple, so the user can know who is nearest first, and don’t have to scroll down to see that Elina is nearest. To do so, we can add this portion of code before returning the list of items:

    // items : variable containing all the items

    // SORT
    for(let a=items.length;a>0;a--)
    {
       for(let b=0;b<a-1;b++)
       {
          if(items[b].distance>items[b+1].distance) // we order by distance
          {
             // we swap the items
             tmp = items[b];
             items[b]=items[b+1];
             items[b+1]=tmp;
          }
       }
    }

    // returning the response for AWS Lambda
    const response = {
        statusCode: 200,
        body: JSON.stringify(items),
    };
    return response;
};

New response:

[
   {
      name: "Elina",
      gender: "woman",
      distance: 2.5
   },
   {
      name: "Paul",
      gender: "man",
      distance: 4.1
   },
   {
      name: "Philip",
      gender: "man",
      distance: 4.9
   }
]

Google Cloud Function VS AWS Lamdba (how to import)

13/07/2021 Nicolas Baptista AWS, Google Cloud 0 Comments

There are some differences between Google Cloud and AWS when you want to deploy your function for your API.

My point of view is that Google Cloud function may be a bit more simple to deploy but AWS is in a way the most reliable and complete cloud environnement nowadays.

On both cloud environnement you can upload the code with a ZIP, you can so use the same way to adjust your code for AWS:

We will upgrade the code with a repository that will be in a ZIP

Differences between Google Cloud functions and AWS Lambda (Node.JS)

THE DEPENDENCIES
– In Google Cloud, the dependencies are automatically installed from the package.json file
– In AWS, you need to install the dependencies with npm or yarn, that will build the node_modules folder
If you don’t have the node_modules folder, your Lamdba function will not work with the following error:

{
  "errorType": "Runtime.ImportModuleError",
  "errorMessage": "Error: Cannot find module 'MODULE'\nRequire stack:\n- /var/task/index.js\n- /var/runtime/UserFunction.js\n- /var/runtime/index.js",
  "trace": [
    "Runtime.ImportModuleError: Error: Cannot find module 'MODULE'",
...

THE MAIN FUNCTION

With Google Cloud, the example function looks like this:

exports.helloWorld = (req, res) => {

  res.status(200).send(message);
};
  • You use the res object with the send() method to send the response

With AWS, the example function looks like this:

exports.handler = async (event) => {

    const response = {
        statusCode: 200,
        body: JSON.stringify(jsonObj),
    };
    return response;
};
  • You return a JSON object response that should contains the body and the statusCode

So the same code will looks like this:

Using parameters

Let’s say now we want to use a parameter for our route, that will be number and the value will be 10, so we will call the route helloWorld?number=10

On GOOGLE CLOUD, to get the “number” parameter, we will use the req object :

exports.helloWorld = (req, res) => {
    let number = req.query.number;

On AWS, to get the “number” parameter, we will use the event object :

exports.handler = async (event) => {
    let number = event["params"]["number"];

Create quickly API with AWS – Lambda/API Gateway

13/07/2021 Nicolas Baptista AWS, Javascript, REST API 0 Comments
Amazon Web Services — Wikipédia

This article is dedicated to new users to AWS – Amazon Web Services – that wants to use this cloud instead for others (Azure, Google Cloud) which seems to be the best choice at the moment. Indeed, AWS is the most complete scalable and dynamic cloud solution.

However, this is not so simple to understand all the concepts, if you look for simplicity you may be interested by Google Cloud that I used before.

In order to use API Gateway and Lamdba, you should add them in favorite in the Services:

Create your API functions in AWS Lambda

We can use AWS Lamdba to create routes that can be used for our applications.

So, you can click Create function, in order to see the form bellow.
Let’s say we want to create a route to list the products of our app, it will be a GET method and we will call it getProducts.
We will use Node.JS because I have to habit to use Javascript and Typescript but you can choose the runtime you are in ease.

Then you can click Create function, we don’t need the others settings.

You should be now able to see the function overview with the default example in the code editor:

You can try the example it will show the string “Hello from Lambda”, the response that is returned in the example.
We can now write our own function from scratch here or alternatively we can upload our code from a ZIP file.

Create our API Gateway route (HTTP)

In the overview of the Lambda function you can see the button Add trigger, you can use it to add the API event that will call our function.

Click “Add trigger”
Select “Create API”, then “HTTP API” (best for cost) and “Open” the endpoint so your app can use it

You can then click Save and so you should see your new trigger, the API Gateway trigger:

Now you can try it by going on the API endpoint link in the details.
You can use it like it in your application or you can change it by adding your own domain, for exemple api.myapp.com/getProducts
You can do that in Custom Domain Names or directly in your domain provider, in the DNS configuration, making a redirection.

Creating an API Gateway (REST API)

You could also, if you need it, use multiple methods such GET, POST, UPDATE, DELETE, … if you created a REST API Gateway :

You can then use your Lambda function for each methods you want to use.

Color picker with React.JS

01/07/2021 Nicolas Baptista Hooks, Javascript, Material UI 0 Comments
Example of a color picker made with React.JS

In order to have a color picker on our React.JS application, we can use the SketchPicker library

Full example

Color: <TextField variant="outlined" id="standard-basic" style={{padding: 5, width: '90%', background: color}} value={color?color:''} onChange={(e) => { setColor(e.target.value); }} />
<SketchPicker 
   color={ color?color:'#fff' }
   onChangeComplete={ (colorSelected) => {
         setColor(`${colorSelected.hex}${decimalToHex(colorSelected.rgb.a)}`);
      } 
   }
   presetColors={['#D0021B', '#F5A623', '#F8E71C', '#8B572A', '#7ED321', '#417505', '#BD10E0', '#9013FE', '#4A90E2', '#50E3C2', '#B8E986', '#000000', '#4A4A4A', '#9B9B9B', '#FFFFFF']}
/>

Alerting user with a small messaga bubble – Snackbar – React.JS

01/07/2021 Nicolas Baptista Hooks, Javascript, Material UI 0 Comments

In your web app, you will have to notice the user when he is doing some actions in your user interface. We can do it with a small message bubble called Snackbar, here is what it looks like:

How we will do it

setSnackSeverity("error");
setSnackMessage("The last cell cannot be deleted.");
setOpenError(true);

In your code, we will use these 3 lines to:
– Set the severity “error”, there are 4 types of severity

– Set the error message that will be displayed “The last cell cannot be deleted.”
– Show the error message (during few seconds)

Full example

import Snackbar from '@material-ui/core/Snackbar';
import MuiAlert, { AlertProps } from '@material-ui/lab/Alert';
function Alert(props) {
  return <MuiAlert elevation={6} variant="filled" {...props} />;
}
...
const [snackSeverity, setSnackSeverity] = useState('error');
const [openError, setOpenError] = useState(false);
const [snackMessage,setSnackMessage] = useState('Error');
...
setSnackSeverity("error");
setSnackMessage("The last cell cannot be deleted.");
setOpenError(true);
...
<Snackbar
   anchorOrigin={{ vertical: 'bottom', horizontal: 'right' }}
   open={openError}
   onClose={(e)=>setOpenError(false)}
   autoHideDuration={3000} 
   >
     <Alert onClose={(e)=>setOpenError(false)} severity={snackSeverity}>
       {snackMessage}
     </Alert>
</Snackbar>

React.JS • Full list of all icons

17/06/2021 Nicolas Baptista Hooks, Javascript, React.JS 0 Comments

Examples of listing the icons in React.JS / React Native

Listing all the icons

List of all the icons

Searching icons name

Searching an icon name

How to do it ?

Importing all the icons

Import the CSS your icons in /public/index.html

<link rel="stylesheet" href="http://cdn.materialdesignicons.com/5.4.55/css/materialdesignicons.min.css" />

Use it in your source code

Use your icons in the code source in /src/App.js like that:

<span> 
   <i class={`mdi mdi-${icon?icon:''}`} aria-hidden="true"></i>
</span>

Loop on all icons

If you want a list of icons then you can loop on the list of icons, let’s say you have put all your icons in a file called iconlist.js 

export const icons = [
"ab-testing",
"abjad-arabic",
"abjad-hebrew",
"abugida-devanagari",
"abugida-thai",
"access-point",
"access-point-check",
"access-point-minus",
"access-point-network",
"access-point-network-off",
"access-point-off",
"access-point-plus",
"access-point-remove",
"account",
"account-alert",
"account-alert-outline",
"account-arrow-left",
"account-arrow-left-outline",
"account-arrow-right",
"account-arrow-right-outline",
"account-box",
"account-box-multiple",
"account-box-multiple-outline",
"account-box-outline",
"account-cancel",
"account-cancel-outline",
"account-cash",
"account-cash-outline",
"account-check",
...
];

Then you can import the icons in you App.js and use it:

import { icons } from './icons';
...
{ icons.map((icon, index) => (
   <div style={{fontWeight: 'bold'}}> <i class={`mdi mdi-${icon}`} aria-hidden="true"></i> {icon} </div>
))}

You can then add a filter if you want to check that the icons contain part of the string name :

const [searchIcon, setSearchIcon] = useState(null);
...
{ icons.filter(icon => icon.includes(searchIcon) ).map((icon, index) => (
    <div style={{fontWeight: 'bold'}}> <i class={`mdi mdi-${icon}`} aria-hidden="true"></i> {icon} </div>
  )
)}

List of the FCA (UK) regulated Forex brokers

16/06/2021 Nicolas Baptista MetaTrader 0 Comments

Here is the full list of this date (JUN 2021) of the brokers regulated by the FCA (UK), one of the most reliable regulator in the world for forex trading.

NAMECOUNTRYREGULATORS LISTTYPE
Doo PrimeVanuatuFCA (UK), VFSC (Vanuatu), FSC (Mauritius)STP, ECN, NDD
Key To MarketsUnited KingdomFCA (UK), DMCC (Dubai)ECN
FxProUnited KingdomFCA (UK), CySEC (Cyprus), SCB (The Bahamas), FSCA (South Africa)NDD
PepperstoneAustraliaFCA (UK), CySEC (Cyprus), ASIC (Australia)STP, ECN, DMA
FxviewCyprusCySEC (Cyprus), FCA (UK), BaFIN (Germany), CONSOB (Italy)STP, ECN, DMA
FOREX.comUnited StatesNFA (US), CFTC (US), FCA (UK), FSA (Japan),
ASIC (Australia), CIMA (Cayman Islands)		Market Maker
AxiAustraliaFCA (UK), ASIC (Australia), FSCA (South Africa), DFSA (Denmark)Market Maker
ForexTimeCyprusCySEC (Cyprus), FCA (UK), IFSC (Belize), FSCA (South Africa)STP, ECN, Market Maker
TickmillUnited KingdomFCA (UK), CySEC (Cyprus), FSCA (South Africa), LFSA (Labuan),
FSA (Seychelles)		STP, NDD

ReactJS • Responsive UI interface

13/06/2021 Nicolas Baptista Javascript, React.JS 0 Comments

You are making a React application and you want to have a responsive user interface that works both on laptop and mobile phone ?

A solution can be to use Material UI with several layout components such :

  • Container
  • Grid
  • Hidden

The grid looks like this:

<Grid container spacing={3}>
        <Grid item xs={12}>
          <Paper className={classes.paper}>xs=12</Paper>
        </Grid>
        <Grid item xs={6}>
          <Paper className={classes.paper}>xs=6</Paper>
        </Grid>
        <Grid item xs={6}>
          <Paper className={classes.paper}>xs=6</Paper>
        </Grid>
        <Grid item xs={3}>
          <Paper className={classes.paper}>xs=3</Paper>
        </Grid>
        <Grid item xs={3}>
          <Paper className={classes.paper}>xs=3</Paper>
        </Grid>
        <Grid item xs={3}>
          <Paper className={classes.paper}>xs=3</Paper>
        </Grid>
        <Grid item xs={3}>
          <Paper className={classes.paper}>xs=3</Paper>
        </Grid>
      </Grid>

As you can see, the full width of the page is xs=12. It means the full width size is equal to 12.


You can see so that with 2 grid items of xs=6, it will be two components.
And so 4 will be 3 components on the line and 3 will be 4 components on the line.

You can use this grid items when you want to display block of contents on the page, if you know Bootstrap, it’s the same.

You can put any content inside your <Grid>, it can be a <div> for example.

Using XS, SM, MD, LG and XL

Grid SizeDeviceWeb browser width
XSMobile phone screens 0px ► 600x
SMMobile phone and tablets600px ► 960px
MDLaptop960px ► 1280px
LGLaptop1280px ► 1920px
XLDesktop1920px ► …

Using breakpoints

Using breakpoints allow you to have different grid size for different devices, which allows you to have a grid adapted for mobile phone for exemple:

You can se the size 6 for laptop (SM=6 and higher) and size is 12 for mobile phone (XS=12)

Using Hidden

You can use the <Hidden> element from Material UI to hide specific items for XS/SM/MD/LG/XL items.

<Hidden only="lg">
    <Paper className={classes.paper}>Hidden on lg</Paper>
</Hidden>

Git commands on production server & Git issues

16/05/2021 Nicolas Baptista Git, Server Maintenance 0 Comments

The following commands can be used on a production server.
In the case of a local machine development, use free software like GIT DESKTOP / SourceTree

First deployment in a folder

git clone <URL GITLAB/GITHUB HTTPS>

Updating / Getting last changes

git pull

The following commands respond to particular problems that may arise.

Changing the URL of a GIT Repository

This problem can occur if you are using GITLAB or GITHUB with SSH and you want to switch to HTTPS or vice versa, or following problems with the rights of an SSH key such as “remote: The project you were looking for could not be found.” and “fatal: Could not read from remote repository.”

Checking the repository URL:

git remote -v

Changing the URL of the repository:

git remote set-url origin <URL>

You cannot pull the changes “You have unstaged changes”

You may get the following error, indicating that some files have changed and need to be committed when you haven’t touched anything and just want to update the server:

Cannot pull with rebase: You have unstaged changes. 
Please commit or stash them.

In order the solve this problem we should remove all the unstaged changes:

git reset --hard

You can now use the git pull command.

Back to the previous commit

git reset --hard HEAD^

Back to a specific commit

git reset --hard <ID COMMIT>

The commit ID is usually 7 digits and hexadecimal letters, example:
26b47fa

You can find it in the history tab of your GIT DESKTOP

Deleting a Commit in the Middle of the History

The two previous commands can delete commits but they are removing from the begining (the most recents commits). It is possible that we want for example to keep the most recent commit and delete a commit in the middle of the history. Replace “sha1-commit-hash” with the ID of the commit BEFORE the first commit you want to delete. For example, if you want to delete the 2nd, 3rd commit in a chronological order, then put the ID of the 4th commit, in a way to see the 3 commits in the editor.

git rebase -i <sha1-commit-hash>

This will open the editor. On the line of the commit you want to remove, change the text “pick” to “drop“.

drop ab12345678 feat: feature to delete # empty
pick cd12345678 feat: important feature

# Rebase ab12345678..cd12345678 onto ef12345678 (2 commands)
#
# Commands:
# p, pick <commit> = use commit
# r, reword <commit> = use commit, but edit the commit message
# e, edit <commit> = use commit, but stop for amending
# s, squash <commit> = use commit, but meld into previous commit
# f, fixup [-C | -c] <commit> = like "squash" but keep only the previous
#                    commit's log message, unless -C is used, in which case
#                    keep only this commit's message; -c is same as -C but
#                    opens the editor
# x, exec <command> = run command (the rest of the line) using shell
# b, break = stop here (continue rebase later with 'git rebase --continue')
# d, drop <commit> = remove commit
:x!

Use :x! to save your modifications and then check it in Git Desktop history or git log command.

Tips: if you have several commits to delete, you can use 2,$s/pick/drop/c to replace (it will ask if you want to replace with “Y” yes or “N” no)

Then you can git push –force to push it on the remote repository.

Overwrite changes on the distant repository (local > remote)

git push --force origin master

Caution, delete on the distant repository, useful if you want to “delete” a commit that has been pushed.

Overwrite changes on the local repository (remote > local)

git reset --hard origin/master

Caution, deletes all the changes made not pushed to the remote git, useful if you want to “delete” the commits locally to have the same thing as on the remote git.

Nicolas BAPTISTA