Regex
Contents
Syntax
This section is under construction. |
Metacharacters
Definitions | Examples | ||
---|---|---|---|
MChar | Definition | Pattern | Sample Matches |
^ | Start of a string. | ^abc | abc, abcdefg, abc123, ... |
$ | End of a string. | abc$ | abc, endsinabc, 123abc, ... |
. | Any character (except \n newline) | a.c | abc, aac, acc, adc, aec, ... |
| | Alternation. | bill|ted | ted, bill |
{...} | Explicit quantifier notation. | ab{2}c | abbc |
[...] | Explicit set of characters to match. | a[bB]c | abc, aBc |
(...) | Logical grouping of part of an expression. | (abc){2} | abcabc |
* | 0 or more of previous expression. | ab*c | ac, abc, abbc, abbbc, ... |
+ | 1 or more of previous expression. | ab+c | abc, abbc, abbbc, ... |
? | 0 or 1 of previous expression; also forces minimal matching when an expression might match several strings within a search string. |
ab?c | ac, abc |
\ | Preceding one of the above, it makes it a literal instead of a special character. Preceding a special matching character, see below. |
a\sc | a c |
Character Escapes
Escaped Char | Description |
---|---|
Ordinary Characters | Characters other than $ . ^ { [ ( | ) ] } * + ? \ match themselves. |
\a | Matches a bell (alarm) \u0007. |
\b | Matches a backspace \u0008 if in a [ ]; otherwise matches a word boundary (between \w and \W characters). |
\t | Matches a tab \u0009. |
\r | Matches a carriage return \u000D. |
\v | Matches a vertical tab \u000B. |
\f | Matches a form feed \u000C. |
\n | Matches a new line \u000A. |
\e | Matches an escape \u001B. |
\040 | Matches an ASCII character as octal (up to three digits); numbers with no leading zero are backreferences if they have only one digit or if they correspond to a capturing group number. For example, the character \040 represents a space. |
\x20 | Matches an ASCII character using hexadecimal representation (exactly two digits). |
\cC | Matches an ASCII control character; for example \cC is control-C. |
\u0020 | Matches a Unicode character using a hexadecimal representation (exactly four digits). |
\* | When followed by a character that is not recognized as an escaped character, matches that character. For example, \* is the same as \x2A. |
Character Classes
Char Class | Description |
---|---|
. | Matches any character except \n. If modified by the Singleline option, a period character matches any character. |
[aeiou] | Matches any single character included in the specified set of characters. |
[^aeiou] | Matches any single character not in the specified set of characters. |
[0-9a-fA-F] | Use of a hyphen (–) allows specification of contiguous character ranges. |
\p{name} | Matches any character in the named character class specified by {name}. Supported names are Unicode groups and block ranges. For example, Ll, Nd, Z, IsGreek, IsBoxDrawing. |
\P{name} | Matches text not included in groups and block ranges specified in {name}. |
\w | Matches any word character. Equivalent to the Unicode character categories [\p{Ll}\p{Lu}\p{Lt}\p{Lo}\p{Nd}\p{Pc}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \w is equivalent to [a-zA-Z_0-9]. |
\W | Matches any nonword character. Equivalent to the Unicode categories [^\p{Ll}\p{Lu}\p{Lt}\p{Lo}\p{Nd}\p{Pc}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \W is equivalent to [^a-zA-Z_0-9]. |
\s | Matches any white-space character. Equivalent to the Unicode character categories [\f\n\r\t\v\x85\p{Z}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \s is equivalent to [ \f\n\r\t\v]. |
\S | Matches any non-white-space character. Equivalent to the Unicode character categories [^\f\n\r\t\v\x85\p{Z}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \S is equivalent to [^ \f\n\r\t\v]. |
\d | Matches any decimal digit. Equivalent to \p{Nd} for Unicode and [0-9] for non-Unicode, ECMAScript behavior. |
\D | Matches any nondigit. Equivalent to \P{Nd} for Unicode and [^0-9] for non-Unicode, ECMAScript behavior. |
More Examples
Symbol | Function |
---|---|
[\^$.|?*+() | Special characters any other will match themselves |
\ | Escapes special characters and treat as literal |
* | Repeat the previous item zero or more times |
. | Single character except line break characters |
.* | Match zero or more characters |
^ | Match at the start of a line/string |
$ | Match at the end of a line/string |
.$ | Match a single character at the end of line/string |
^ $ | Match line with a single space |
[^A-Z] | Match any line beginning with any char from A to Z |
Examples
Samples
- Matching specific value from output
Source: pythex.org:
%Cpu(s): 0.3 us, 0.1 sy, 0.0 ni, 99.3 id, 0.2 wa, 0.0 hi, 0.0 si, 0.1 st %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,1.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
Regex:
([0-9]{3}.[0-9]|[0-9]{2}.[0-9]|[0-9].[0-9])(?=\sid)
Explanation:
[0-9]{3} => 3 digits | => OR [0-9]{2} => 2 digits . => any character (Dot here) (?=\sid) => select non-greedy output before 'id' ? => non-greedy \s => Space id => 'id' character
IP Addresses
- To Match upto 999.999.999.999:
\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b
OR shortened with a quantifier to:
\b(?:\d{1,3}\.){3}\d{1,3}\b
- To match exactly upto 255.255.255.255:
\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b
OR shortened with a quantifier to:
\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b
Credit Card numbers
Visa card numbers start with a 4. New cards have 16 digits. Old cards have 13:
^4[0-9]{12}(?:[0-9]{3})?$
MasterCard numbers start with the numbers 51 through 55. All have 16 digits:
^5[1-5][0-9]{14}$
Misc Examples
- Match 2 characters/numbers only:
^[0-9a-zA-Z]{2}$
- Simple URL Verification:
(http|https):\/\/([a-z])\w+\.(com|net|org)