RegEx never ending story….

Regex is an essential tool in every developer’s tool-bag. It helps you perform a search in strings. Regex is used everywhere from compilers to word processors.

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Problem with SQL IN(…)

It is an example to use Regexp to prepare SQL data for SELECT/UPDATE operation. Regexp: /^.*/gm and substitution: '�',

Explanation

1. ^ asserts position at start of a line
2. .* matches any character (except for line terminators)
3. * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
4. Global pattern flags
   1. >g modifier: global. All matches (don’t return after first match)
   2. m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)

Example how to use it

This example simple replaces MBS to ,'MBS'. For example, when you have many selected values in SQL (in one column) and need to convert it to running query.

SELECT * FROM TABLE WHERE ID IN( AAA AAB AAC ...)

Convert it to:

SELECT * FROM TABLE WHERE ID IN( 'AAA', 'AAB', 'AAC')

Example in practice: https://regex101.com/r/34repv/1 or https://extendsclass.com/regex-tester.html#MTkxMTI1MTNkZTM5MmRjYWY1

solution

Try to find playlist in YouTube URL

(?:https?:\/\/)?(?:youtu\.be\/|(?:www\.|m\.)?youtube\.com\/(?:playlist|list|embed)(?:\.php)?(?:\?.*list=|\/))([a-zA-Z0-9\-_]+)

Test this example

1. https://regex101.com/r/p8x4GU/2

Good tools for testing regex

• https://regex101.com/ and here is this example: https://regex101.com/r/34repv/1
• https://extendsclass.com/regex-tester.html#MTkxMTI1MTNkZTM5MmRjYWY1 (very good graphics explanation)
• https://pythonium.net/regex 
• https://regexr.com/
• https://rustexp.lpil.uk/

How is run in editors and system?

Visual Code 

• https://marketplace.visualstudio.com/items?itemName=chrmarti.regex
• https://github.com/roberthgnz/visual-regex

Try to use Ubuntu in WSL2 | in Medium on W10 or Cygwin there are tools line grep, sed ect.

Regular Expressions Cheat Sheet

A regular expression specifies a set of strings that matches it. This cheat sheet is based off Python 3’s Regular Expressions (http://docs.python.org/3/library/re.html) but is designed for searches within Sublime Text. Simple example:

grep -E "^(regular|expressions)$" regex.txt grep -E "(re)gular expssions" regex.txt grep -E '^([0-9]{4}[- ]?){3}[0-9]{4} credit-card.txt grep '^[[:space:]]* regex.txt grep -E '\<([[:alpha:]]+)[[:space:]]+\>' regex.txt

more you can find in https://linuxconfig.org/understanding-regular-expressions