Regex: List of Metacharacters
Positional
| Metacharacter | Description |
|---|---|
^ |
Beginning of line |
$ |
End of line |
\A |
Beginning of string |
\z |
End of string |
\Z |
End of string (excluding line endings) |
\b |
Word boundaries |
\B |
Non-word boundaries |
- The
^and$are used as “beginning and end of line” but this is the case in multiline mode (usually this is the default). In single-line mode, it is the beginning or end of the entire string.
Special characters
| Metacharacter | Description |
|---|---|
\ |
Escape |
\t |
Tab |
\n |
Newline (CR) |
\r |
Newline (LF) |
\f |
New page |
\d |
Digits |
\D |
Non-digits |
\s |
Whitespace (space, tab, neewline and new page) |
\S |
Non-whitespace |
\w |
Word (alphanumeric characters plus ”_“) |
\W |
Non-word |
Wildcards and repetition (quantity specifiers)
| Default | Lazy | Greedy | Description |
|---|---|---|---|
. |
Any one character (excluding line feed code) | ||
* |
*? |
*+ |
0 or more occurrences of the preceding item |
+ |
+? |
++ |
1 or more occurrences of the preceding item |
? |
?? |
?+ |
0 or 1 occurrences of the preceding item |
{n} |
{n}? |
{n}+ |
n occurrences of the preceding item |
{n,} |
{n,}? |
{n,}+ |
n or more occurrences of the preceding item |
{n,m} |
{n,m}? |
{n,m}+ |
n or more and not more than m occurrences of the preceding item |
Default
Match the longest part that matches the condition. Preference is given to matching the entire pattern.
Lazy
Match the shortest part that matches the condition.
Greedy
Match the longest part that matches the condition. No preference is given to matching the entire pattern.
e.g. abcXdefX
| Regex | Result | |
|---|---|---|
| Default | ^.*X |
abcXdefX |
| Lazy | ^.*?X |
abcX |
| Greedy | ^.*+X |
Not match.* |
| Greedy | ^.*+ |
abcXdefX |
(*) ^.*+ matches all “abcXdefX”, so the last X does not match.
Select from candidates
| Metacharacter | Description |
|---|---|
() |
Blocking |
| |
Or (strings) |
[] |
Or (one character) |
e.g. |
| Metacharacter | Description |
|---|---|
abc|mno|xyz |
Simple abc, mno, or xyz |
abc.*X|m+o|xy?z |
Include metachar in candidates abcXXX, mXo, xz, etc. |
(abc|mno|xyz)X |
Combine with other strings abcX, mnoX, or xyzX |
(abc|mno|xyz)* |
Combine with quantity specifiers abcabc, mnoabcxyz, etc. |
e.g. []
| Metacharacter | Description |
|---|---|
[abc] |
Simple (a, b, or c) |
[^abc] |
Negation (Other than a, b, c) |
[a-z] |
Range (lowercase) |
[A-Z] |
Range (uppercase) |
[0-9] |
Range (digits) |
[a-zA-Z] |
Or (a to z or A to Z) |
[a-z&&[d-f]] |
And (a to z and d to f) |
[a-z&&[^d-f]] |
Subtraction (a to z excluding d to f) |
Lookahead and Lookbehind
| Meta | Description | e.g. | Description |
|---|---|---|---|
?= |
Positive lookahead | foo(?=bar) |
Matches “foo” followed by “bar”. |
?! |
Negative lookahead | foo(?!bar) |
Matches “foo” not followed by “bar”. |
?<= |
Positive lookbehind | (?<=bar)foo |
Matches “foo” preceded by “bar”. |
?<! |
Negative lookbehind | (?<!bar)foo |
Matches “foo” not preceded by “bar”. |