RegEX Cheat Sheet

REGEXP\_INSTR(expr, pat[, pos[, occurrence[, return\_option[, match\_type]]]])

#Examples

mysql> SELECT regexp_instr('aa aaa aaaa', 'a{3}');
2
mysql> SELECT regexp_instr('abba', 'b{2}', 2);
2
mysql> SELECT regexp_instr('abbabba', 'b{2}', 1, 2);
5
mysql> SELECT regexp_instr('abbabba', 'b{2}', 1, 3, 1);
7

REGEXP\_LIKE(expr, pat[, match\_type])

#Examples

mysql> SELECT regexp_like('aba', 'b+')
1
mysql> SELECT regexp_like('aba', 'b{2}')
0
mysql> # i: case-insensitive
mysql> SELECT regexp_like('Abba', 'ABBA', 'i');
1
mysql> # m: multi-line
mysql> SELECT regexp_like('a\nb\nc', '^b$', 'm');
1

REGEXP\_SUBSTR(expr, pat[, pos[, occurrence[, match\_type]]])

#Examples

mysql> SELECT REGEXP_SUBSTR('abc def ghi', '[a-z]+');
abc
mysql> SELECT REGEXP_SUBSTR('abc def ghi', '[a-z]+', 1, 3);
ghi

REGEXP\_REPLACE(expr, pat, repl[, pos[, occurrence[, match\_type]]])

#Examples

mysql> SELECT REGEXP_REPLACE('a b c', 'b', 'X');
a X c
mysql> SELECT REGEXP_REPLACE('abc ghi', '[a-z]+', 'X', 1, 2);
abc X

expr REGEXP pat 

#Examples

mysql> SELECT 'abc' REGEXP '^[a-d]';
1
mysql> SELECT name FROM cities WHERE name REGEXP '^A';
mysql> SELECT name FROM cities WHERE name NOT REGEXP '^A';
mysql> SELECT name FROM cities WHERE name REGEXP 'A|B|R';
mysql> SELECT 'a' REGEXP 'A', 'a' REGEXP BINARY 'A';
1   0

#Pattern

• Pattern compile(String regex [, int flags])
• boolean matches([String regex, ] CharSequence input)
• String[] split(String regex [, int limit])
• String quote(String s)

#Matcher

• int start([int group | String name])
• int end([int group | String name])
• boolean find([int start])
• String group([int group | String name])
• Matcher reset()

#String

• boolean matches(String regex)
• String replaceAll(String regex, String replacement)
• String[] split(String regex[, int limit]) There are more methods …

#First way

Pattern p = Pattern.compile(".s", Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher("aS");  
boolean s1 = m.matches();  
System.out.println(s1);   // Outputs: true

#Second way

boolean s2 = Pattern.compile("[0-9]+").matcher("123").matches();  
System.out.println(s2);   // Outputs: true

#Third way

boolean s3 = Pattern.matches(".s", "XXXX");  
System.out.println(s3);   // Outputs: false

$str = "Jane\tKate\nLucy Marion";
$regex = "@\s@";
// Output: Array("Jane", "Kate", "Lucy", "Marion")
print\_r(preg\_split($regex, $str));

$arr = ["Jane", "jane", "Joan", "JANE"];
$regex = "/Jane/";
// Output: Jane
echo preg\_grep($regex, $arr);

$regex = "/[a-zA-Z]+ (\d+)/";
$input\_str = "June 24, August 13, and December 30";
if (preg\_match\_all($regex, $input\_str, $matches\_out)) {
    // Output: 2
    echo count($matches\_out);
    // Output: 3
    echo count($matches\_out[0]);
    // Output: Array("June 24", "August 13", "December 30")
    print\_r($matches\_out[0]);
    // Output: Array("24", "13", "30")
    print\_r($matches\_out[1]);
}

$str = "Visit QuickRef";
$regex = "#quickref#i";
// Output: 1
echo preg\_match($regex, $str);

$str = "Visit Microsoft!";
$regex = "/microsoft/i";
// Output: Visit QuickRef!
echo preg\_replace($regex, "QuickRef", $str); 

let regex = /apples/gi;
let text = 'Here are apples and apPleS';
// Output: Here are mangoes and mangoes
let result = text.replaceAll(regex, "mangoes");
console.log(result);

let text = 'Do you like aPPles?';
let regex = /apples/i

// Output: Do you like mangoes?
let result = text.replace(regex, 'mangoes');
console.log(result);

let regex = /t(e)(st(\d?))/g;
let text = 'test1test2';
let array = [...text.matchAll(regex)];
// Output: ["test1", "e", "st1", "1"]
console.log(array[0]);
// Output: ["test2", "e", "st2", "2"]
console.log(array[1]);

let text = 'This 593 string will be brok294en at places where d1gits are.';
let regex = /\d+/g

// Output: [ "This ", " string will be brok", "en at places where d", "gits are." ] 
console.log(text.split(regex))

let text = 'Here are apples and apPleS';
let regex = /apples/gi;

// Output: [ "apples", "apPleS" ]
console.log(text.match(regex));

let text = 'Do you like apples?';
let regex= /apples/;

// Output: apples
console.log(regex.exec(text)[0]);

// Output: Do you like apples?
console.log(regex.exec(text).input);

let text = 'I like APPles very much';
let regexA = /apples/;
let regexB = /apples/i;

// Output: -1
console.log(text.search(regexA));

// Output: 7
console.log(text.search(regexB));

let textA = 'I like APPles very much';
let textB = 'I like APPles';
let regex = /apples$/i

// Output: false
console.log(regex.test(textA));

// Output: true
console.log(regex.test(textB));

#re.search()

>>> sentence = 'This is a sample string'
>>> bool(re.search(r'this', sentence, flags=re.I))
True
>>> bool(re.search(r'xyz', sentence))
False

#re.findall()

>>> re.findall(r'\bs?pare?\b', 'par spar apparent spare part pare')
['par', 'spar', 'spare', 'pare']
>>> re.findall(r'\b0\*[1-9]\d{2,}\b', '0501 035 154 12 26 98234')
['0501', '154', '98234']

#re.finditer()

>>> m_iter = re.finditer(r'[0-9]+', '45 349 651 593 4 204')
>>> [m[0] for m in m_iter if int(m[0]) < 350]
['45', '349', '4', '204']

#re.split()

>>> re.split(r'\d+', 'Sample123string42with777numbers')
['Sample', 'string', 'with', 'numbers']

#re.sub()

>>> ip_lines = "catapults\nconcatenate\ncat"
>>> print(re.sub(r'^', r'\* ', ip_lines, flags=re.M))
* catapults
* concatenate
* cat

#re.compile()

>>> pet = re.compile(r'dog')
>>> type(pet)
<class '\_sre.SRE\_Pattern'>
>>> bool(pet.search('They bought a dog'))
True
>>> bool(pet.search('A cat crossed their path'))
False

Match "Mr." or "Ms." if word "her" is later in string

M(?(?=.*?\bher\b)s|r)\.

requires lookaround for IF condition

If alternatives overlap, order longer to shorter.

Can lead to catastrophic backtracking.

• ^
• {
• +
• <
• [
• *
• )
• >
• .
• (
• |
• $
• \
• ? Escape these special characters with \

This is a quick cheat sheet to getting started with regular expressions.

• Regex in Python (quickref.me)
• Regex in JavaScript (quickref.me)
• Regex in PHP (quickref.me)
• Regex in Java (quickref.me)
• Regex in MySQL (quickref.me)
• Regex in Vim (quickref.me)
• Regex in Emacs (quickref.me)
• Online regex tester (regex101.com)