#regularexpression

[chidrestechtutorials]

Quantifiers in Regular Expression JavaScript:

- Learn how to use Quantifiers with Regular Expressions in JavaScript

Visit: https://youtu.be/Tegfrydjn84

[kindsonthegenius]

Day 28 - Regex, Patterns and Introduction to Databases - HackerRank 30 D...

[gauravchowmean]

Log parsing in python using regular expressions.

Log parsing in python using regular expressions.

Log parsing is a very basic problem for DevOps and SREs and we have a post on this regarding log parsing. You can find the post here

https://learnsteps.com/log-parsing-in-python-read-how-you-can-do-it/

In the earlier post, I have not used regex and have used only string manipulations to parse the logs.

What is a regular expression?

Regular expressions are a sequence of…

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[superaakash24]

JavaScript Regular Expression - How to Create & Write them in JavaScript - DataFlair

Get all the concepts clear related to JavaScript Regular Expression. Learn how to create and write Regular Expression in JavaScript with examples.

[smartcherryposts]

Regular Expression s

Regular Expression s Are Used For Representing  Certain Sets Of Strings In A Algebraic Function.  

Rules

1) Any Terminal Symbol i.e Symbols ε, Σ Including ∧(Empty) And Φ(Phi) Are Regular Expresions. Example:- Input Symbols Like a,b,1,0,∧,Φ Are Regular Expresions   2) The Union Of Two Regular Expresions Is Also A Regular Expresion. Example-R1,R2 (R1,R2) Is A Regular Expresion.   3) The Concatenation Of Two Regular Expressions Is Also A Regular Expresion. Example- R1,R2---->(R1.R2)   4) The Iteration(Or Closure) Of A Regular Expresion Is Also A Regular Expresion. Example-R--->R*(Closure Of R Is R*) Example 2-a--->a* a*={a,a,aa,aaa,......}   If 'a' Is The Regular Expresion a* Is The Closure Of 'a'(Regular Expresion) a* Means The Set Of Strings Formed By 'a', Infinite Strings, See Below. a*={∧,a,aa,aaa,aaaa,...} //   ∧ Is Empty String If 'a' Is Regular Expresion Then Its Closure 'a*' Will Also Be Regular Expresion.   5) The Regular Expression Over Σ Are Precisely Those Obtained Recursively By The Application Of The Above Rules Once Or Several Times. Means This Rule Say's "All The Regular Expressions Over Sigma(Σ) What Are They? They Are Simply The Regular Expresions That Are Obtained By Applying The Rules 1,2,3,4 Which Are Given Above Once Or Many Times. When We Do The Union Of Regular Expresion (or) Concatenation (or) Closure, We Will Get New Regular Expresions.   Read the full article

[milindjagre]

So I just became klout identified expert in scripting language and regular expression 🤘🏼😎 #klout_instagram #klout #expert #regularexpression #scriptinglanguage #developer #coder #studentlife (at Ford NA Learning & Development)

[whatsthatwei-blog]

Regular Expression.  Why.

Have you ever encountered the same solution to a problem time after time again, never fully grasping why it works, but accepting that it does?  And because this magical solution works so well and you’ve got bigger fish to fry, you put off researching why it works and choose to just accept that it’s magic and you shouldn’t question it?

That’s what regular expression is to me.  Up until last week, when Gee slacked me “I’ve actually been interested in learning more about regex, like regular expression,” I didn’t realize that “regular expression” was what this magic was called.

The first time I ever (unknowingly) used regex, was when I was trying to make myself a contact form for my personal website back in 2010 and I needed a way to make sure that the email was valid.

Here is part of the javascript email validation I used in my code.:

var hasError = false; var emailReg = /^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$/; var emailFromVal = $("#emailFrom").val(); if(emailFromVal == '') { $("#emailFrom").after('Please enter a valid email address.'); hasError = true; } else if(!emailReg.test(emailFromVal)) { $("#emailFrom").after('Please enter a valid email address.'); hasError = true; }

/^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}$/;

How does one get from that gibberish to email validation??

I ran into Regular Expression a few more times since then, most notably in the Ruby labs we had to do at the Flatiron School.  For example, one of our labs instructed us to be able to break a paragraph string into sentences.  To do so, we needed to find a way to identify punctuation.

So, I turned to stack overflow:

string = "I am a lion. Hear me roar! Where is my cub? Never mind, found him." string.gsub(/[.?!]/, '\0|') # "I am a lion.| Hear me roar!| Where is my cub?| Never mind, found him.|"

Okay, I can kind of begin to understand what's gong on.  I think.  It’s obvious to me that, /[.?!]/ is basically searching for punctuation in the string.  Which makes a lot of sense, because Regular Expression (regex) is “a special text string for describing a search pattern.”  A wildcard on steroids, if you will.

https://www.reddit.com/r/explainlikeimfive/comments/w1e0p/eli5_how_do_regexeswork/c59gb18/

Regular Expression basically gives you a list of things to look for in a particular sequence with forward slashes often encapsulating the regex.  /hello/ - look for an ‘h’ followed by ‘e’ followed by ‘l,’ and so on.  Where it gets complex is when factor in special characters that give things special meanings.

And suddenly the gibberish from above makes sense!

/^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}$/;

/.../ - surrounds the regex used.  ^ and $ are anchor characters signifying start-of-string and end-of-string.  The [ .. ] looks for any character listed or in the range specified, followed by + which is basically looking for one or more of any character in the brackets.  So basically, this expression is looking for a collection of any of the characters in the bracket (A-Z and a-z, numbers, and some select symbols) followed by an @ sign, followed by another collection of characters (A-Z and a-z, numbers, ‘-’ and ‘.’ which takes into account subdomains), a “.” (the literal since it’s escaped by a backslash), and another collection of characters (A-Z and a-z) that is greater than 2.

[sarutc]

ignore case search in vi editor

Today tip

which  “SED” command you can use  s/[reg pattern]/i   for search / replace ignore case  but when you want to search on vi  you have to use \c on any position of string 

example use vi editor open mysql dump file and search “InnoDB” 

/innodb/i <--- wrong 

/\cinnodb  <--- correct