Regular Expressions by Everett Benzel

a sequence of characters that specifies a match pattern in text - Wikipedia

Some patterns to consider...

Alternates

• ab|d - or
• [abe] - one of
• [^abe] - anything but
• [a-c] - range

Anchors

• ^a - start of string
• $a - end of string

Lookarounds

• a(?=c) - followed by
• a(?!c) - not followed by
• (?<=b)c - preceded by
• (?< !b)c - not preceded by

Quantifiers

• a? - zero or one a
• a* - zero or more a
• a+ - one or more a
• a{n} - exactly n a
• a{n,} - n or more a