Regular expression reference table list
| Regular Expression | Explanation |
|---|---|
| a-z | matches small letters starting from 'a' - 'z' |
| A-Z | matches capital letters starting from 'A' - 'Z' |
| . | dot(.) represents single wildcard character (joker in a card game) |
| \ | escape character. To escape the actual representation and represent actual character |
| ^ | is used to negate a batch of character like [^a-z] -- matches the characters other than 'a' - 'z' |
| \d | digits |
| {m, n} | m, n are integers here. represents any preceding character appears atleast 'm' times and atmost 'n' times. ex: a[1, 3] 'a' can appear 1-3 times |
| * | represents the preceding expression can occur from 0 to any number of times. ex: \d* any digit can appear from 0 to any number of times |
| + | represents the preceding expression will occur atleast once. ex: \d+ - digit will appear atleast once. |
| ? | represents the preceding character is optional(it may occur). ex: a? -- the match may have 'a' & ab?c -- 'b' is optional. |
| \w | represents alphanumeric [a-zA-Z0-9_] |
| - | space |
| \t | tab |
| \n | newline |
| \r | carriage return |
| \s | space (represents space, tab, newline or carriage return) |
| ^....$ | ^ starting an expressiong and $ represents ending of the expression |
| () | capturing part |
| | | OR (cats|dogs|birds) - cats or dogs or birds |
| \b | boundary between a word and a non-word character. |
| Any expression written in CAPITAL LETTER represents opposite of actual definition ex: \D - non digits \W - non alphanumeric \S - non whitespace |
|
| Referencing any captured groups using parenthesis('()') --- there can be many groups clubbed together and to refer each group use ex: (\d*\.([,\d*]?))*$ \0 - full matched text \1 - group 1 \2 - group 2 |