Cisco Cisco Email Security Appliance C160 Mode D'Emploi
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Cisco IronPort AsyncOS 7.1 for Email Advanced Configuration Guide
OL-22164-02
Chapter 5 Using Message Filters to Enforce Email Policies
Guide), or using a text editor to generate a file that is then imported into the
system. For more information, see
system. For more information, see
.
Guidelines for Using Regular Expressions
It is important to begin a regular expression with a caret (
^
) and end it with a dollar
sign (
$
) whenever you want to exactly match a string and not a prefix.
Note
When matching an empty string, do not use
“”
as that actually matches all strings.
Instead use
“^$”
. For an example, see the second example in
It is also important to remember that if you want to match a literal period, you
must use an escaped period in the regular expression. For example, the regular
expression
must use an escaped period in the regular expression. For example, the regular
expression
sun.com
matches the string
thegodsunocommando
, but the regular
expression
^sun\.com$
only matched the string
sun.com.
Technically, the style of regular expressions used are Python re Module style
regular expressions. For a more detailed discussion of Python style regular
expressions, consult the Python Regular Expression HOWTO, accessible from
regular expressions. For a more detailed discussion of Python style regular
expressions, consult the Python Regular Expression HOWTO, accessible from
:
http://www.python.org/doc/howto/
Regular Expression and Non-ASCII Character Sets
In some languages, the concepts of a word or word boundary, or case do not exist.
Complex regular expressions that depend on concepts like what is or is not a
character that would compose a word (represented as “
character that would compose a word (represented as “
\w
” in regex syntax) cause
problems when the locale is unknown or if the encoding is not known for certain.