I want to understand RegEx! (Part1)

Have you ever been a witness of such dialogues? Have you ever understood what the people talking about if they mention RegEx? Do you want to speak this language? Then, read this series of the blogs about RegEx.

RegEx is a huge part and we can talk about it a long time. There are a lot of good blogs and videos to this topic and it takes a lot of time to understand all of them.

In this article I want to give you a short introduction into "RegEx-World". I want you to understand what this mean and how you can use it. And If you decide to became a RegEx professional then you need to read more blogs or books also to watch more videos :).

But let's start step by step

Idea of RegEx:

Imagine you have data like this:
website.com/domain/orderpage.html?productcat=shoes&brand=12345 Moin St.&shoenumber=12345&color=black.www.bluewebsite.com/domain/orderpage.html?=Michle/productcat=shoes&brand=3456 Silvester St.&shoenumber=5678&color=www.bluewebsite1.com/domain/orderpage.html?=Jennifer/productcat=shoes&brand=3456 Silvester St.nike&shoenumber=123423&color=www.bluewebsite2.com/domain/orderpage.html?productcat=shoes&brand=nike&shoenumber=12345&color=red

And you want to extract all names, address, websites and colors. In order to do this, you need RegEx.

In other words you have to say your program:

"Look through the text and extract all names, addresses, websites and colors!"

Imagine the program, you are using, is a stranger and it doesn't speak your language. It understands only RegEx as a language.

At first I would like to extract all address (12345 Moin St.; 3456 Silvester St.) . Thus I'll say to the program:  "Look at all postal codes and Street Names"

In order to say something on RegEx language you have to use RegEx signs. 

Postal Codes: 12345

\d{1,5} (d for digit; 1,5 - The postal code is a number with min 1 and max 5 digits )

\s (for space)

Street Name:Moin St.

\w+ (for a word different length)

\s

\w+

\.

And this is my sentence in the RegEx language: 

\d{1,5}\s\w+\s\w+\.

Note!
Every single string is separated with \

Here are some basic RegEx signs for you:

/d   Represent any number
/D   Represent anything but a number
/s    Represent space
/S   Represent anything but space
/w   Represent any character
/W  Represent anything but character
/b   is a zero with assertion. That means it does not match a character, it matches a position with one thing on the left side and another thing on the right side. (A Cat)
\e   Escape
\f   Form Feed
\n   Newline
\r   Carriage Return
\t   Tab

?        you are looking for 0 or 1 repetitions
*        0 or more repetitions
{n}     you know exactly number of repetitions you are looking for (e.g. number of postal code)
[a-z]   you are looking for every single lowercase letter
[A-Z] you are looking for every single uppercase letter
[0-9]  you are looking for every single number


Examples:

You are looking for "Michle".
The RegEx for this: 'Michle\s'

You are looking for a dollar amount
$100.00
The RegEx for this: \$\d*\.\d{2}

I defenetly advise you to watch this tutorial.It helped me to understand RegEx:

• Learn RegEx

This links could be helpful:

• Become a regex regular & wrangle imperfect data
• RegEx Check
• Tutorial to RegEx

I hope you understand now how to use and speak RegEx....