Common Regular Expression Grammar Quick Reference Table

Expression	Name/Description	Example	Matches
.	Any single character except newline	a.b	aab, acb, a b
[aeiou]	Character set: matches any one character inside brackets	[aeiou]	a, e, I
[^0-9]	Negated set: matches any character not inside brackets	[^0-9]	a, #, (space)
\d	Matches any digit. Same as `[0-9]`	\d	0, 1, 9
\w	Matches any word character. Same as `[a-zA-Z0-9_]`	\w	a, B, 5, _
\s	Matches any whitespace (space, tab, form-feed, etc.)	\s	`, \t, \n
^	Matches the start of the string	^hello	hello world
$	Matches the end of the string	world$	hello world
*	Matches preceding element zero or more times	a*	"" (empty), a, aaa
+	Matches preceding element one or more times	a+	a, aaa
?	Matches preceding element zero or one time	a?	"" (empty), a
{n}	Matches preceding element exactly n times	\d{3}	123, 456
{n,}	Matches preceding element at least n times	\d{2,}	12, 123, 1234
{n,m}	Matches preceding element at least n but no more than m times	\d{2,4}	12, 1234
( )	Group, treats expression inside as a single unit	(ab)+	ab, abab

Common Examples

Email Address

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

Phone Number (CN)

^1[3-9]\d{9}$

ID Card (CN)

^\d{15}$ |\d{18}$

Common Modifiers

i (case-insensitive)

Ignores case while matching. /hello/i matches Hello, HELLO, hello.

g (global)

Finds all matches, not just the first. /a/g matches three 'a's in 'banana'.

m (multiline)

Makes `^` and `$` match line start/end instead of string start/end.

s (single-line/dot-all)

Makes `.` match newlines as well.

Usage Tips

Use online tools (like RegexToolBox) to test and debug patterns in real time. Start simple and build up complexity. Remember to escape backslashes in string literals depending on your programming language.

Common Regular Expression Grammar Quick Reference Table

Common Examples

Email Address

Phone Number (CN)

ID Card (CN)

Common Modifiers

i (case-insensitive)

g (global)

m (multiline)

s (single-line/dot-all)

Usage Tips

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