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cheatsheets.pdf's Introduction
Regular Expression Cheat Sheet - PCRE
| Anchor |
Description |
Example |
Valid match |
Invalid |
| ^ |
start of string or line |
^foam |
foam |
bath foam |
| \A |
start of string in any match mode |
\Afoam |
foam |
bath foam |
| $ |
end of string or line |
finish$ |
finish |
finnish |
| \Z |
end of string, or char before last new line in any match mode |
finish\Z |
finish |
finnish |
| \z |
end of string, in any match mode. |
|
|
|
| \G |
end of the previous match or the start of the string for the first match |
^(get|set)|\G\w+$ |
setValue |
seValue |
| \b |
word boundary; position between a word character (\w), and a nonword character (\W) |
\bis\b |
This island is beautiful |
This island isn't beautiful |
| \B |
not-word-boundary. |
\Bland |
island |
peninsula |
| Assertion |
Description |
Example |
Valid match |
Invalid |
| (?=...) |
positive lookahead |
question(?=s) |
questions |
question |
| (?!...) |
negative lookahead |
answer(?!s) |
answer |
answers |
| (?<=...) |
positive look-behind |
(?<=appl)e |
apple |
application |
| (?<!...) |
negative look-behind |
(?<!goo)d |
mood |
good |
| Char class |
Description |
Example |
Valid match |
Invalid |
| [ ] |
class definition |
[axf] |
a, x, f |
b |
| [ - ] |
class definition range |
[a-c] |
a, b, c |
d |
| [ \ ] |
escape inside class |
[a-f.] |
a, b, . |
g |
| [^ ] |
Not in class |
[^abc] |
d, e |
a |
| [:class:] |
POSIX class |
[:alpha:] |
string |
0101 |
| . |
match any chars except new line |
b.ttle |
battle, bottle |
bttle |
| \s |
white space, [\n\r\f\t ] |
good\smorning |
good morning |
good.morning |
| \S |
no-white space, [^\n\r\f\t] |
good\Smorning |
goodmorning |
good morning |
| \d |
digit |
\d{2} |
23 |
1a |
| \D |
non-digit |
\D{3} |
foo, bar |
fo1 |
| \w |
word, [a-z-A-Z0-9_] |
\w{4} |
v411 |
v4.1 |
| \W |
non word, [^a-z-A-Z0-9_] |
.$%? |
.$%? |
.ab? |
| Special character |
Description |
| |general escape |
|
| \n |
new line |
| \r |
carriage return |
| \t |
tab |
| \v |
vertical tab |
| \f |
form feed |
| \a |
alarm |
| [\b] |
backspace |
| \e |
escape |
| \cchar |
Ctrl + char(ie:\cc is Ctrl+c) |
| \ooo |
three digit octal (ie: \123) |
| \xhh |
one or two digit hexadecimal (ie: \x10) |
| \x{hex} |
any hexadecimal code (ie: \x{1234}) |
| \p{xx} |
char with unicode property (ie: \p{Arabic} |
| \P{xx} |
char without unicode property |
| Sequence |
Description |
Example |
Valid match |
Invalid |
| | |
alternation |
apple|orange |
apple, orange |
melon |
| ( ) |
subpattern |
foot(er|ball) |
footer or footbal |
footpath |
| (?P<name>...) |
subpattern, and capture submatch into name |
(?P<greeting>hello) |
hello |
hallo |
| (?:...) |
subpattern, but does not capture submatch |
(?:hello) |
hello |
hallo |
| + |
one or more quantifier |
ye+ah |
yeah, yeeeah |
yah |
| * |
zero or more quantifier |
ye*ah |
yeeah, yeeeah, yah |
yeh |
| ? |
zero or one quantifier |
yes? |
yes, ye |
yess |
| ?? |
zero or one, as few times as possible (lazy) |
yea??h |
yeah |
yeaah |
| +? |
one or more lazy |
/<.+?>/g |
<P>foo</P> matches only <P> and </P> |
|
| *? |
zero or more, lazy |
/<.*?>/g |
<html> |
|
| {n} |
n times exactly |
fo{2} |
foo |
fooo |
| {n,m} |
from n to m times |
go{2,3}d |
good,goood |
gooood |
| {n,} |
at least n times |
go{2,} |
goo, gooo |
go |
| (?(condition)...) |
if-then pattern |
(<)?[p](?(1)>) |
<p>, p |
<p |
| (?(condition)...|...) |
if-then-else pattern |
`^(?(?=q)que |
ans)` |
question, answer |
| Pattern modifier |
Description |
| g |
global match |
| i |
case-insensitiv, match both uppercase and lowercase |
| m |
multiple lines |
| s |
single line (by default) |
| x |
ingore whitespace allows comments |
| A |
anchored, the pattern is forced to ^ |
| D |
dollar end only, a dollar metacharacter matches only at the end |
| S |
extra analysis performed, useful for non-anchored patterns |
| U |
ungreedy, greedy patterns becomes lazy by default |
| X |
additional functionality of PCRE (PCRE extra) |
| J |
allow duplicate names for subpatterns |
| u |
unicode, pattern and subject strings are treated as UTF-8 |
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