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RegEx (Regular Expressions)...

Powerful, expressive and flexible.. ..

 


RegEx > Basic RegEx Syntax


Regular expresions programs can get complex, dirty and scary - just admit it, the language doesn't look very friendly - when you first stumble across it, it's like looking into an unflushed toilet (what, ugghh...yuck, nasty).

But once, you've realised, the language is actually very compact and beautiful (once you've mastered LaTeX you look at it a different way) The syntax only looks scary as you don't know it yet! It's fast, minimalistic and (super) powerful (and dangerous).

The following gives you an overview of the syntax, symbols and their meaning.


do not be overwhelmed and let it get messy
Don't get overwhelmed by regular expressios and let things get messy! They're actually very logical



Regular expressions (regex) use a special set of symbols and characters to describe patterns in text.

Here are some key components:

1. Literals: Regular letters and numbers match themselves. For example, the regex cat will match the sequence of characters "cat" in a text.

2. Metacharacters: Special characters with special meanings. Examples include:

  • . (dot): Matches any single character except for a newline.
  • ^: Anchors the regex at the start of a line.
  • $: Anchors the regex at the end of a line.

3. Character Classes: Square brackets [] are used to define a set of characters. For instance, [aeiou] matches any vowel. You can also specify ranges like [0-9] to match any digit.

4. Quantifiers: Control the number of times a character or group of characters can appear.

  • *: Matches zero or more occurrences.
  • +: Matches one or more occurrences.
  • ?: Matches zero or one occurrence.
  • {n}: Matches exactly n occurrences.
  • {n,}: Matches n or more occurrences.
  • {n,m}: Matches between n and m occurrences.

5. Anchors: Characters that anchor the regex to the start or end of a line.

  • ^: Matches the start of a line.
  • $: Matches the end of a line.

6. Groups and Capture: Parentheses () are used to group parts of a pattern. They also help capture specific portions of the matched text for further use.

7. Escape Characters: Some characters have special meanings, but you might want to match them literally. Use a backslash \ to escape them. For example, \. will match a literal dot.

8. Alternation: The pipe | allows you to match either the pattern on its left or the pattern on its right. For example, cat|dog will match either "cat" or "dog."

These are the fundamental building blocks of regular expressions. When combined, they allow you to create powerful patterns for searching, matching, and manipulating text in a flexible and efficient way. Regular expressions might look a bit cryptic at first, but with practice, they become a handy tool in your coding toolkit.

Remember, regex might look a bit cryptic at first, but it becomes a powerful tool for searching and manipulating text!


















 
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