The following list highlights characters and operators most frequently
used in regular expressions:
- \
- Quotes the character that follows it, which treats that character
as a literal character or operator (not a regular expression). When
you want the following characters to be treated as literal, you must
precede them with a backslash:
* ? + [ ( ) { } ^ $ | \ . /
In
other words, use a backslash followed by a forward slash (\/)
to include a forward slash in a URI filter. Use a backslash followed
by a period (\.) to include a period in a URI filter.
Example: to specify the URI pattern
http://www.ibm.com/,
use the following regular expression:
http:\/\/www\.ibm\.com\/
To
specify all URIs that begin with
http://www.ibm.com/,
use the following regular expression:
http:\/\/www\.ibm\.com\/.*
- .
- Matches any one character.
Example: to match both ibm2 and ibm3 within
a string, use ibm. such as in the following example: http:\/\/www\.ibm.\.com\/
- (?: … )
- Non-capturing parentheses. Groups the included pattern, but does
not provide capturing of matching text. Somewhat more efficient than
capturing parentheses.
Example: you can use the non-capturing
parenthesis to group expressions to form more complicated regular
expressions. To match a URI that starts with one of the following
URLs:
http://www.ibm.com/marketing/ or
http://www.ibm.com/sales/,
you would do a grouping with a pipe sign (|) (represents
or):
http://www.ibm.com/(?:marketing)|(?:sales)/
- *
- Matches the preceding element zero or more times. You must quote
this character.
Example: the expression, ca*t,
matches cat, caat, ct,
and caaaaat. The term cabt, would
not return as a match.