. |
Any character except newline. |
\. |
A period (and so on for \*, \(, \\, etc.) |
^ |
The start of the string. |
$ |
The end of the string. |
\d,\w,\s |
A digit, word character [A-Za-z0-9_], or whitespace. |
\D,\W,\S |
Anything except a digit, word character, or whitespace. |
[abc] |
Character a, b, or c. |
[a-z] |
a through z. |
[^abc] |
Any character except a, b, or c. |
aa|bb |
Either aa or bb. |
? |
Zero or one of the preceding element. |
* |
Zero or more of the preceding element. |
+ |
One or more of the preceding element. |
{n} |
Exactly n of the preceding element. |
{n,} |
n or more of the preceding element. |
{m,n} |
Between m and n of the preceding element. |
??,*?,+?,
{n}?, etc. |
Same as above, but as few times as possible. |
(expr) |
Capture expr for use with \1, etc. |
(?:expr) |
Non-capturing group. |
(?=expr) |
Followed by expr. |
(?!expr) |
Not followed by expr. |