Regular expressions

You can use several ordinary and special characters in a regular expression.
Table 1. Special characters and their meanings
Character Meaning Example
^ Matches the beginning of the string "^abc" matches strings starting with abc
$ Matches the end of the string "abc$" matches strings ending with abc
. Matches any single character "a.c$" matches strings containing abc, axc, and so on
* Matches zero or more of the immediately preceding expression "ab*c$" matches strings containing ac, abc, abbc, and so on
+ Matches one or more of the immediately preceding expression "a+c$" matches strings containing abc, abbc, aggc, but not ac
? Matches zero or one of the immediately preceding expression "ab?c" matches strings containing ac or abc
| Matches either the preceding or following expression. "a|b|c" matches strings containing a, b, or c
[ ] Matches any single character listed between brackets "[ab]c" matches strings containing ac or bc
[^ ] Matches any single character not listed between brackets. "a[^b]c" matches strings containing axc for any replacement of x except for b
\ Escapes the character which immediately follows. To embed a backslash character in a string, the string literal must contain two consecutive backslashes. "a\.c$" matches strings containing a.c, and "a\\c$" matches strings containing a\c
( ) Delimits subexpressions "a(b|c)*d*" matches strings containing a followed by any number of bs or cs followed by d, such as "ad" or "acbbccd"

Feedback