© 2024 R-Tools Technology Inc.
All rights reserved.
Regular expression is a notation for patterns of text, as opposed to exact strings of characters. The notation uses literal characters and metacharacters. Every character which does not have special meaning in the regular-expression syntax is a literal character and matches an occurrence of that character. For example, letters and numbers are literal characters. A metacharacter is a symbol with special meaning (an operator or delimiter) in the regular-expression syntax.
. |
Wildcard: any character |
* |
Repeat: zero or more occurrences of previous character or class |
^ |
Line position: beginning of line |
$ |
Line position: end of line |
[class] |
Character class: any character in the set |
[^class] |
Inverse class: any character not in the set |
[x-y] |
Range: any characters within the specified range |
\x |
Escape: literal use of metacharacter x |
\<xyz |
Word position: beginning of the word |
xyz\> |
Word position: end of the word |
For example, the following regular expression .* matches any string of characters, ^a matches any string beginning with character a.