| A | B |
|---|
| "Regular Expression" (abbreviated) | regex |
| metacharacter | character not taken literally |
| literal | normal text character |
| anchor | metacharacter matching a position |
| [... ] character class | matches any one of several characters |
| dash (-) between 2 chars in character class | indicates range of chars |
| [^...] negated character class | matches any char not listed |
| dot (.) | matches any character |
| or, bar (|) | separates alternative subexpressions |
| parentheses (...) | create subexpression (grouping) |
| quantifiers (?, +, *) | indicate number of occurences of previous item |
| ...? (question mark) | zero or one occurences of previous item |
| ...* (star, asterisk) | zero or more occurences of previous item |
| ...+ (plus) | at least one occurence of previous item |
| described by a regex | a set of strings satisfying certain constraints |
| ^... | begin of line (anchor) |
| ...$ | end of line (anchor) |
| \w (lower case) | part-of-word char [a-zA-Z0-9_] |
| \W (capital) | non-word char [^w] |
| \d (lower case) | digit [0-9] |
| \D (capital) | non digit [^0-9] |
| \s (lower case) | whitespace character [ \f\n\r\t\v] |
| \S (capital) | non-whitespace character [^\s] |
| escaping | neutralizing a metacharacter (reducing it to text) |
| \char (if combination is not metadescriptive) | escaped char |
| \t | tab character |
| \r | return character |
| \n | newline character |
| ...{min,max} | repeat previous at least min times, but not more than max times |
| ...{min,} (comma!) | repeat previous item at least min times |
| ...{num} (no comma) | repeat previous item num times |
| grouping | putting part of a regex between parentheses (creates a subexpression) |
| \ followed by a digit | back reference to the digith subexpression (between parentheses) |
