The Building Blocks of Regular Expressions

Regular expressions are constructed from a combination of elements, each with a specific purpose:

• Literals: These are characters or sequences of characters that are matched exactly as they appear in the regular expression. For example, the regex abc will match the sequence "abc" within a string.
• Metacharacters: These are special characters that have a reserved meaning within regular expressions. Some common metacharacters include:
  • . (Dot): Matches any single character except newline.
  • \: Escapes a metacharacter, allowing it to be treated as a literal.
  • [ ]: Matches any one of the characters inside the brackets.
• Quantifiers: These specify how many occurrences of the preceding element are allowed. They include:
  • *: 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.
  ...