Creating Regular Expressions online, use this site.
For more look here.
| Character | Legend | Example | Sample Match |
|---|
| \d | Most engines: one digit from 0 to 9 | file_\d\d | file_25 |
| \d | .NET, Python 3: one Unicode digit in any script | file_\d\d | file_9੩ |
| \w | Most engines: “word character”: ASCII letter, digit or underscore | \w-\w\w\w | A-b_1 |
| \w | .Python 3: “word character”: Unicode letter, ideogram, digit, or underscore | \w-\w\w\w | 字-ま_۳ |
| \w | .NET: “word character”: Unicode letter, ideogram, digit, or connector | \w-\w\w\w | 字-ま‿۳ |
| \s | Most engines: “whitespace character”: space, tab, newline, carriage return, vertical tab | a\sb\sc | a b c |
| \s | .NET, Python 3, JavaScript: “whitespace character”: any Unicode separator | a\sb\sc | a b c |
| \D | One character that is not a digit as defined by your engine’s \d | \D\D\D | ABC |
| \W | One character that is not a word character as defined by your engine’s \w | \W\W\W\W\W | *-+=) |
| \S | One character that is not a whitespace character as defined by your engine’s \s | \S\S\S\S | Yoyo |
| Quantifier | Legend | Example | Sample Match |
|---|
| + | One or more | Version \w-\w+ | Version A-b1_1 |
| {3} | Exactly three times | \D{3} | ABC |
| {2,4} | Two to four times | \d{2,4} | 156 |
| {3,} | Three or more times | \w{3,} | regex_tutorial |
| * | Zero or more times | ABC* | AAACC |
| ? | Once or none | plurals? | plural |
| Character | Legend | Example | Sample Match |
|---|
| . | Any character except line break | a.c | abc |
| . | Any character except line break | .* | whatever, man. |
| . | A period (special character: needs to be escaped by a ) | a.c | a.c |
| \ | Escapes a special character | .*+? $^/\ | .*+? $^/\ |
| \ | Escapes a special character | [{()}] | [{()}] |
| Logic | Legend | Example | Sample Match |
|---|
| | | Alternation / OR operand | 22|33 | 33 |
| ( … ) | Capturing group | A(nt|pple) | Apple (captures “pple”) |
| \1 | Contents of Group 1 | r(\w)g\1x | regex |
| \2 | Contents of Group 2 | (\d\d)+(\d\d)=\2+\1 | 12+65=65+12 |
| (?: … ) | Non-capturing group | A(?:nt|pple) | Apple |
| Character | Legend | Example | Sample Match |
|---|
| \t | Tab | T\t\w{2} | T ab |
| \r | Carriage return character | see below | |
| \n | Line feed character | see below | |
| \r\n | Line separator on Windows | AB\r\nCD | ABCD |
| \N | Perl, PCRE (C, PHP, R…): one character that is not a line break | \N+ | ABC |
| \h | Perl, PCRE (C, PHP, R…), Java: one horizontal whitespace character: tab or Unicode space separator | | |
| \H | One character that is not a horizontal whitespace | | |
| \v | .NET, JavaScript, Python, Ruby: vertical tab | | |
| \v | Perl, PCRE (C, PHP, R…), Java: one vertical whitespace character: line feed, carriage return, vertical tab, form feed, paragraph or line separator | | |
| \V | Perl, PCRE (C, PHP, R…), Java: any character that is not a vertical whitespace | | |
| \R | Perl, PCRE (C, PHP, R…), Java: one line break (carriage return + line feed pair, and all the characters matched by \v) | | |
| Quantifier | Legend | Example | Sample Match |
|---|
| + | The + (one or more) is “greedy” | \d+ | 12345 |
| ? | Makes quantifiers “lazy” | \d+? | 1 in 12345 |
| * | The * (zero or more) is “greedy” | A* | AAA |
| ? | Makes quantifiers “lazy” | A*? | empty in AAA |
| {2,4} | Two to four times, “greedy” | \w{2,4} | abcd |
| ? | Makes quantifiers “lazy” | \w{2,4}? | ab in abcd |
| Character | Legend | Example | Sample Match |
|---|
| [ … ] | One of the characters in the brackets | [AEIOU] | One uppercase vowel |
| [ … ] | One of the characters in the brackets | T[ao]p | Tap or Top |
| - | Range indicator | [a-z] | One lowercase letter |
| [x-y] | One of the characters in the range from x to y | [A-Z]+ | GREAT |
| [ … ] | One of the characters in the brackets | [AB1-5w-z] | One of either: A,B,1,2,3,4,5,w,x,y,z |
| [x-y] | One of the characters in the range from x to y | [ -~]+ | Characters in the printable section of the ASCII table. |
| [^x] | One character that is not x | [^a-z]{3} | A1! |
| [^x-y] | One of the characters not in the range from x to y | [^ -~]+ | Characters that are not in the printable section of the ASCII table. |
| [\d\D] | One character that is a digit or a non-digit | [\d\D]+ | Any characters, including new lines, which the regular dot doesn’t match |
| [\x41] | Matches the character at hexadecimal position 41 in the ASCII table, i.e. A | [\x41-\x45]{3} | ABE |
grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b"
$ nmcli | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b"
10.10.10.32
0.0.0.0
10.10.10.0
169.254.0.0
grep -o '[^/]*\.<domain>\.com'
(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9]))\.){3}(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])
