RegEx (Regular Expressions Basic Primer)
00:00 Intro
00:24 Where its used
02:31 RegEx how to create
03:10 Understanding RegEx with the examples
Utilize metacharacters to define patterns. Some common metacharacters:
= . (dot): Matches any single character except a newline.
= *: Matches zero or more occurrences of the preceding element.
= +: Matches one or more occurrences of the preceding element.
= ?: Matches zero or one occurrence of the preceding element.
= (): Create a group for matching and capturing.
= []: Defines a character class to match any character from the set.
= {}: Specify a quantifier to match a specific number of occurrences.
= |: Acts as an OR operator, allowing you to match one of several alternatives.
Examples
1. Matching a Specific Word:
Regex: apple
Explanation: This regex matches the exact word "apple" in a text.
2. Matching Digits:
Regex: [0-9]
Explanation: This regex matches any single digit from 0 to 9.
3. Matching Multiple Digits:
Regex: [0-9]+
Explanation: This regex matches one or more consecutive digits.
4. Matching Alphanumeric Characters:
Regex: [a-zA-Z0-9]
Explanation: This regex matches any single alphanumeric character (letters and digits).
5. Matching Email Addresses (Simplified):
Regex: [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
Explanation: This regex matches a simplified form of email addresses. It checks for the basic structure of an email with one "@" symbol and a valid domain.
6. Matching Dates in YYYY-MM-DD Format:
Regex: \d{4}-\d{2}-\d{2}
Explanation: This regex matches dates in the format YYYY-MM-DD, where \d represents any digit.
7. Matching URLs (Simplified):
Regex: https?://[^\s]+
Explanation: This regex matches simplified URLs starting with "http://" or "https://". [^\s]+ matches one or more characters that are not whitespace.
8. Matching Phone Numbers (US Format):
Regex: \(\d{3}\) \d{3}-\d{4}
Explanation: This regex matches US phone numbers in the format (123) 456-7890. It uses escaped parentheses \( and \), and \d to match digits.
9. Matching Words with Hyphens:
Regex: [a-zA-Z]+-?[a-zA-Z]+
Explanation: This regex matches words that may contain a single hyphen, allowing for words like "self-contained" or "test."
10. Matching Whitespace Characters:
Regex: \s+
Explanation: This regex matches one or more whitespace characters (spaces, tabs, or line breaks).