Regular Expression Features

Regular Expression Features

The features of patterns used in regular expression can be grouped into serveral categories.

Literals

In a general sense, literals may be considered as printable or unprintable characters. Literals used in regular expression can be any single character of alphanumeric characters, ACSII characters, octal characters, hexadecimal character, UNICODE character, or other special escaped characters. A regular expression engine tries to match each individual literal with the searched string. An individual literal is used for matching one literal to one single substring only. In other words, each literal in the expression should match with one character of the searched string accordingly.

• Alphanumericto matches alphabetical and numerical characters literally and accordingly. i.e. A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
• \* to matches the special metacharacter * literally.
• \+ to matches the special metacharacter + literally.
• \? to matches the special metacharacter ? literally.
• \^ to matches the special metacharacter ^ literally.
• \$ to matches the special metacharacter $ literally.
• \. to matches the special metacharacter . literally.
• \| to matches the special metacharacter | literally.
• \{ to matches the special metacharacter { literally.
• \} to matches the special metacharacter } literally.
• \\ to matches the special metacharacter \ literally.
• \[ to matches the special metacharacter [ literally.
• \] to matches the special metacharacter ] literally.
• \( to matches the special metacharacter ( literally.
• \) to matches the special metacharacter ) literally.
• \f to matches a nonprinting form feed character
• \n to matches a nonprinting new line character
• \r to matches a nonprinting carriage return character
• \t to matches a nonprinting horizontal tab character
• \v to matches a nonprinting vertical tab character
• \xn to matches the ASCII character specified by n literally. n must be a hexadecimal escape value of an ASCII code with exactly two digits.  i.e. \x00-\xFF
• \cx to matches the ASCII control character specified by x literally. x must be in the range of A-Z or a-z, otherwise c is assumed to be a literal "c" character, that is a simple escaped character. i.e. \cA-\cZ and \ca-\cz. The range of represented ASCII characters is equivalent to \x01-\x1A. Lowercase letter is equivalent to Uppercase letter with no difference in meaning.
• \nml to matches the extended ASCII character specified by nml literally unless there is a backreference corresponding to the specified number. As an octal escape character, nml must be an octal escape value of an extended ASCII character. i.e. 0-377 or 000-377
• \un to matches the Unicode character specified by n literally. n must be a hexadecimal escape value of a Unicode code with exactly four digits. i.e. 0000-FFFF

A table of extended ASCII literals can be compared as following and n/a stands for not applicable.

			literals
DEC	Description of Unprintable Control Codes	SYM	char	escaped char	HEX \xn	\cx	OCT \nml	UNICODE \un
0	Null char	NUL			00		000	0000
1	Start of Heading	SOH			01	A, a	001	0001
2	Start of Text	STX			02	B,b	002	0002
3	End of Text	ETX			03	C,c	003	0003
4	End of Transmission	EOT			04	D,d	004	0004
5	Enquiry	ENQ			05	E,e	005	0005
6	Acknowledgment	ACK			06	F,f	006	0006
7	Bell	BEL			07	G,g	007	0007
8	Back Space	BS			08	H,h	010	0008
9	Horizontal Tab	HT		\t	09	I,i	011	0009
10	Line Feed	LF		\n	0A	J,j	012	000A
11	Vertical Tab	VT		\v	0B	K,k	013	000B
12	Form Feed	FF		\f	0C	L,l	014	000C
13	Carriage Return	CR		\r	0D	M,m	015	000D
14	Shift Out / X-On	SO			0E	N,n	016	000E
15	Shift In / X-Off	SI			0F	O,o	017	000F
16	Data Line Escape	DLE			10	P,p	020	0010
17	Device Control 1 (oft. XON)	DC1			11	Q,q	021	0011
18	Device Control 2	DC2			12	R,r	022	0012
19	Device Control 3 (oft. XOFF)	DC3			13	S,s	023	0013
20	Device Control 4	DC4			14	T,t	024	0014
21	Negative Acknowledgement	NAK			15	U,u	025	0015
22	Synchronous Idle	SYN			16	V,v	026	0016
23	End of Transmit Block	ETB			17	W,w	027	0017
24	Cancel	CAN			18	X,x	030	0018
25	End of Medium	EM			19	Y,y	031	0019
26	Substitute	SUB			1A	Z,z	032	001A
27	Escape	ESC			1B		033	001B
28	File Separator	FS			1C		034	001C
29	Group Separator	GS			1D		035	001D
30	Record Separator	RS			1E		036	001E
31	Unit Separator	US			1F		037	001F
DEC	Description of Printable Codes except char 127	SYM	char	escaped char	HEX \xn	\cx	OCT \nml	UNICODE \un
32	Space				20		040	0020
33	Exclamation mark	!			21		041	0021
34	Double quotes (or speech marks)	"			22		042	0022
35	Number	#			23		043	0023
36	Dollar	$		\$	24		044	0024
37	Procenttecken	%			25		045	0025
38	Ampersand	&			26		046	0026
39	Single quote	'			27		047	0027
40	Open parenthesis (or open bracket)	(		\(	28		050	0028
41	Close parenthesis (or close bracket)	)		\)	29		051	0029
42	Asterisk	*		\*	2A		052	002A
43	Plus	+		\+	2B		053	002B
44	Comma	,			2C		054	002C
45	Hyphen	-			2D		055	002D
46	Period, dot or full stop	.		\.	2E		056	002E
47	Slash or divide	/			2F		057	002F
48	Zero	0	0	n/a	30		060	0030
49	One	1	1	n/a	31		061	0031
50	Two	2	2	n/a	32		062	0032
51	Three	3	3	n/a	33		063	0033
52	Four	4	4	n/a	34		064	0034
53	Five	5	5	n/a	35		065	0035
54	Six	6	6	n/a	36		066	0036
55	Seven	7	7	n/a	37		067	0037
56	Eight	8	8	n/a	38		070	0038
57	Nine	9	9	n/a	39		071	0039
58	Colon	:			3A		072	003A
59	Semicolon	;			3B		073	003B
60	Less than (or open angled bracket)	<			3C		074	003C
61	Equals	=			3D		075	003D
62	Greater than (or close angled bracket)	>			3E		076	003E
63	Question mark	?		\?	3F		077	003F
64	At SYM	@			40		100	0040
65	Uppercase A	A	A		41		101	0041
66	Uppercase B	B	B	n/a	42		102	0042
67	Uppercase C	C	C		43		103	0043
68	Uppercase D	D	D	n/a	44		104	0044
69	Uppercase E	E	E		45		105	0045
70	Uppercase F	F	F		46		106	0046
71	Uppercase G	G	G		47		107	0047
72	Uppercase H	H	H		48		110	0048
73	Uppercase I	I	I		49		111	0049
74	Uppercase J	J	J		4A		112	004A
75	Uppercase K	K	K		4B		113	004B
76	Uppercase L	L	L		4C		114	004C
77	Uppercase M	M	M		4D		115	004D
78	Uppercase N	N	N		4E		116	004E
79	Uppercase O	O	O		4F		117	004F
80	Uppercase P	P	P		50		120	0050
81	Uppercase Q	Q	Q		51		121	0051
82	Uppercase R	R	R		52		122	0052
83	Uppercase S	S	S	n/a	53		123	0053
84	Uppercase T	T	T		54		124	0054
85	Uppercase U	U	U		55		125	0055
86	Uppercase V	V	V		56		126	0056
87	Uppercase W	W	W	n/a	57		127	0057
88	Uppercase X	X	X		58		130	0058
89	Uppercase Y	Y	Y		59		131	0059
90	Uppercase Z	Z	Z		5A		132	005A
91	Opening bracket	[		\[	5B		133	005B
92	Backslash	\		\\	5C		134	005C
93	Closing bracket	]		\]	5D		135	005D
94	Caret - circumflex	^		\^	5E		136	005E
95	Underscore	_			5F		137	005F
96	Grave accent	`			60		140	0060
97	Lowercase a	a	a		61		141	0061
98	Lowercase b	b	b	n/a	62		142	0062
99	Lowercase c	c	c	n/a	63		143	0063
100	Lowercase d	d	d	n/a	64		144	0064
101	Lowercase e	e	e		65		145	0065
102	Lowercase f	f	f	n/a	66		146	0066
103	Lowercase g	g	g		67		147	0067
104	Lowercase h	h	h		68		150	0068
105	Lowercase i	i	i		69		151	0069
106	Lowercase j	j	j		6A		152	006A
107	Lowercase k	k	k		6B		153	006B
108	Lowercase l	l	l		6C		154	006C
109	Lowercase m	m	m		6D		155	006D
110	Lowercase n	n	n	n/a	6E		156	006E
111	Lowercase o	o	o		6F		157	006F
112	Lowercase p	p	p		70		160	0070
113	Lowercase q	q	q		71		161	0071
114	Lowercase r	r	r	n/a	72		162	0072
115	Lowercase s	s	s	n/s	73		163	0073
116	Lowercase t	t	t	n/a	74		164	0074
117	Lowercase u	u	u	n/a	75		165	0075
118	Lowercase v	v	v	n/a	76		166	0076
119	Lowercase w	w	w	n/a	77		167	0077
120	Lowercase x	x	x	n/a	78		170	0078
121	Lowercase y	y	y		79		171	0079
122	Lowercase z	z	z		7A		172	007A
123	Opening brace	{		\{	7B		173	007B
124	Vertical bar	|		\|	7C		174	007C
125	Closing brace	}		\}	7D		175	007D
126	Equivalency sign - tilde	~			7E		176	007E
127	Delete				7F		177	007F
DEC	Description of extended ASCII codes (Windows-1252 & ISO 8859-1)	SYM	char	escaped char	HEX \xn	\cx	OCT \nml	UNICODE \un
128	Euro sign	€			80		200	20AC
129					81		201
130	Single low-9 quotation mark	‚			82		202	201A
131	Latin small letter f with hook	ƒ			83		203	0192
132	Double low-9 quotation mark	„			84		204	201E
133	Horizontal ellipsis	…			85		205	2026
134	Dagger	†			86		206	2020
135	Double dagger	‡			87		207	2021
136	Modifier letter circumflex accent	ˆ			88		210	02C6
137	Per mille sign	‰			89		211
138	Latin capital letter S with caron	Š			8A		212
139	Single left-pointing angle quotation	‹			8B		213
140	Latin capital ligature OE	Œ			8C		214
141					8D		215
142	Latin captial letter Z with caron	Ž			8E		216
143					8F		217
144					90		220
145	Left single quotation mark	‘			91		221
146	Right single quotation mark	’			92		222
147	Left double quotation mark	“			93		223
148	Right double quotation mark	”			94		224
149	Bullet	•			95		225
150	En dash	–			96		226
151	Em dash	—			97		227
152	Small tilde	˜			98		230
153	Trade mark sign	™			99		231
154	Latin small letter S with caron	š			9A		232
155	Single right-pointing angle quotation mark	›			9B		233
156	Latin small ligature oe	œ			9C		234
157					9D		235
158	Latin small letter z with caron	ž			9E		236
159	Latin capital letter Y with diaeresis	Ÿ			9F		237
160	Non-breaking space				A0		240	00A0
161	Inverted exclamation mark	¡			A1		241	00A1
162	Cent sign	¢			A2		242	00A2
163	Pound sign	£			A3		243	00A3
164	Currency sign	¤			A4		244	00A4
165	Yen sign	¥			A5		245	00A5
166	Pipe, Broken vertical bar	¦			A6		246	00A6
167	Section sign	§			A7		247	00A7
168	Spacing diaeresis - umlaut	¨			A8		250	00A8
169	Copyright sign	©			A9		251	00A9
170	Feminine ordinal indicator	ª			AA		252	00AA
171	Left double angle quotes	«			AB		253	00AB
172	Not sign	¬			AC		254	00AC
173	Soft hyphen	­			AD		255	00AD
174	Registered trade mark sign	®			AE		256	00AE
175	Spacing macron - overline	¯			AF		257	00AF
176	Degree sign	°			B0		260	00B0
177	Plus-or-minus sign	±			B1		261	00B1
178	Superscript two - squared	²			B2		262	00B2
179	Superscript three - cubed	³			B3		263	00B3
180	Acute accent - spacing acute	´			B4		264	00B4
181	Micro sign	µ			B5		265	00B5
182	Pilcrow sign - paragraph sign	¶			B6		266	00B6
183	Middle dot - Georgian comma	·			B7		267	00B7
184	Spacing cedilla	¸			B8		270	00B8
185	Superscript one	¹			B9		271	00B9
186	Masculine ordinal indicator	º			BA		272	00BA
187	Right double angle quotes	»			BB		273	00BB
188	Fraction one quarter	¼			BC		274	00BC
189	Fraction one half	½			BD		275	00BD
190	Fraction three quarters	¾			BE		276	00BE
191	Inverted question mark	¿			BF		277	00BF
192	Latin capital letter A with grave	À			C0		300	000C
193	Latin capital letter A with acute	Á			C1		301	00C1
194	Latin capital letter A with circumflex	Â			C2		302	00C2
195	Latin capital letter A with tilde	Ã			C3		303	00C3
196	Latin capital letter A with diaeresis	Ä			C4		304	00C4
197	Latin capital letter A with ring above	Å			C5		305	00C5
198	Latin capital letter AE	Æ			C6		306	00C6
199	Latin capital letter C with cedilla	Ç			C7		307	00C7
200	Latin capital letter E with grave	È			C8		310	00C8
201	Latin capital letter E with acute	É			C9		311	00C9
202	Latin capital letter E with circumflex	Ê			CA		312	00CA
203	Latin capital letter E with diaeresis	Ë			CB		313	00CB
204	Latin capital letter I with grave	Ì			CC		314	00CC
205	Latin capital letter I with acute	Í			CD		315	00CD
206	Latin capital letter I with circumflex	Î			CE		316	00CE
207	Latin capital letter I with diaeresis	Ï			CF		317	00CF
208	Latin capital letter ETH	Ð			D0		320	00D0
209	Latin capital letter N with tilde	Ñ			D1		321	00D1
210	Latin capital letter O with grave	Ò			D2		322	00D2
211	Latin capital letter O with acute	Ó			D3		323	00D3
212	Latin capital letter O with circumflex	Ô			D4		324	00D4
213	Latin capital letter O with tilde	Õ			D5		325	00D5
214	Latin capital letter O with diaeresis	Ö			D6		326	00D6
215	Multiplication sign	×			D7		327	00D7
216	Latin capital letter O with slash	Ø			D8		330	00D8
217	Latin capital letter U with grave	Ù			D9		331	00D9
218	Latin capital letter U with acute	Ú			DA		332	00DA
219	Latin capital letter U with circumflex	Û			DB		333	00DB
220	Latin capital letter U with diaeresis	Ü			DC		334	00DC
221	Latin capital letter Y with acute	Ý			DD		335	00DD
222	Latin capital letter THORN	Þ			DE		336	00DE
223	Latin small letter sharp s - ess-zed	ß			DF		337	00DF
224	Latin small letter a with grave	à			E0		340	00E0
225	Latin small letter a with acute	á			E1		341	00E1
226	Latin small letter a with circumflex	â			E2		342	00E2
227	Latin small letter a with tilde	ã			E3		343	00E3
228	Latin small letter a with diaeresis	ä			E4		344	00E4
229	Latin small letter a with ring above	å			E5		345	00E5
230	Latin small letter ae	æ			E6		346	00E6
231	Latin small letter c with cedilla	ç			E7		347	00E7
232	Latin small letter e with grave	è			E8		350	00E8
233	Latin small letter e with acute	é			E9		351	00E9
234	Latin small letter e with circumflex	ê			EA		352	00EA
235	Latin small letter e with diaeresis	ë			EB		353	00EB
236	Latin small letter i with grave	ì			EC		354	00EC
237	Latin small letter i with acute	í			ED		355	00ED
238	Latin small letter i with circumflex	î			EE		356	00EE
239	Latin small letter i with diaeresis	ï			EF		357	00EF
240	Latin small letter eth	ð			F0		360	00F0
241	Latin small letter n with tilde	ñ			F1		361	00F1
242	Latin small letter o with grave	ò			F2		362	00F2
243	Latin small letter o with acute	ó			F3		363	00F3
244	Latin small letter o with circumflex	ô			F4		364	00F4
245	Latin small letter o with tilde	õ			F5		365	00F5
246	Latin small letter o with diaeresis	ö			F6		366	00F6
247	Division sign	÷			F7		367	00F7
248	Latin small letter o with slash	ø			F8		370	00F8
249	Latin small letter u with grave	ù			F9		371	00F9
250	Latin small letter u with acute	ú			FA		372	00FA
251	Latin small letter u with circumflex	û			FB		373	00FB
252	Latin small letter u with diaeresis	ü			FC		374	00FC
253	Latin small letter y with acute	ý			FD		375	00FD
254	Latin small letter thorn	þ			FE		376	00FE
255	Latin small letter y with diaeresis	ÿ			FF		377	00FF