Keyword expressions can be:
-
Groups of literal text characters
-
Patterns, defined using symbols (regular expressions) that describe a range of possible groupings of text
-
A mixture of literal text and symbolic patterns
For example, a keyword expression might be a single word, a
phrase, or even a substring; or it might be a pattern that defines a more general
grouping of text, such as an asterisk used as a wildcard to stand in for any text
of
one or more characters in length.
Regular expressions, often called regexes, are sets of symbols and
syntactic elements used to match patterns of text. The symbols stand in for
character patterns or define how the expression is to be evaluated. Using regular
expressions is sophisticated way to search for complex character patterns in large
blocks of text. For example, suppose you want to search for the occurrence of an
email address—any email address—in a block of text. You can build a regular
expression that will match any pattern of text that has any valid name string,
followed by an @ character, followed by any valid domain name string, followed by
a
period, followed by any valid domain suffix string.
Cloud Email Gateway
Protection uses a subset of POSIX
regular expression syntax.
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TipIf your expression includes the characters \ | ( ) { } [ ] . ^
$ * + or ?, you must escape them by using a \ immediately before the character.
Otherwise, they will be assumed to be regular expression operators rather than
literal characters.
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This help system contains a brief summary of common regex
elements, but a thorough guide to regular expression syntax is beyond the scope of
this help system. However, there are many sources of reference information available
on the Web or in books.