^ = starting of the line
$ = Ending of the line
. = (dot) match any single character
03.10.16
matches 03-10-16, 03/10/16, 30.10.16
* = (asterisk) match zero/more occurrence of previous character
| = combination of two
[ ] = Character class, either of two
Gr[eay] searches both Grey and Gray
<H[12345]>
Finds HTML headers
<H1> <H2> <H3> <H4> <H5>
Metacharacter - both the below are similar.
[0-9a-fA-F]
[0123456789abcdefABCDEF]
Negation - [^...]
[^1-6] → matches the character that is not 1 to 6
Alternation
uses the parentheses ‘(‘ ‘)’
to find first, 1st
(fir|1)st
^(from|subject|date):
matches the start of line and then from or subject or date
Word Boundaries
\< → start of the word
\> → End of word
/<cat/> → finds the word cat
/<cat → finds the word starts with cat
cat/> → word ends with cat
Optional items
?
attaches only to immediately to preceding item.
for matching color or colour
colou?r → u is optional in searching.
Repetition
+ → one or more immediately preceding item
* → any number, including zero.
Escape Character
\
match the dot → \.
match the parenthesis → \( \)
A span of characters
\{ \}
\{n\} -- exactly n occurrences
\{n,\} - atleast n occurrences.
\{n,m\} -- any occurrence between n and m will be matches
For ex
10\{2,4\}1
matches 1001, 10001, 100001
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