What are regular expression patterns

Regular Expressions provide a group of patterns in order to match characters. Basically they are categorized into 3 types,

1. Brackets: These are used to find a range of characters.

For example, below are some use cases,

1. [abc]: Used to find any of the characters between the brackets(a,b,c)

2. [0-9]: Used to find any of the digits between the brackets

3. (a|b): Used to find any of the alternatives separated with |

2. Metacharacters: These are characters with a special meaning.

For example, below are some use cases,

1. \\d: Used to find a digit

2. \\s: Used to find a whitespace character

3. \\b: Used to find a match at the beginning or ending of a word

3. Quantifiers: These are useful to define quantities.

For example, below are some use cases,

1. n+: Used to find matches for any string that contains at least one n

2. n\*: Used to find matches for any string that contains zero or more occurrences of n

3. n?: Used to find matches for any string that contains zero or one occurrences of n