Cisco ASA 5508-X, Configuration Manual

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12-16
Cisco ASA Series Firewall CLI Configuration Guide
Chapter 12 Getting Started with Application Layer Protocol Inspection
Configure Regular Expressions
Procedure
Step 1
Test a regular expression to make sure it matches what you think it will match.
* Asterisk A quantifier that indicates that there are 0, 1 or any
number of the previous expression. For example,
lo*se
matches lse, lose, loose, and so on.
+ Plus A quantifier that indicates that there is at least 1 of the
previous expression. For example,
lo+se matches lose
and loose, but not lse.
{ x } or { x ,} Minimum repeat quantifier Repeat at least x times. For example, ab(xy){2,}z
matches abxyxyz, abxyxyxyz, and so on.
[ abc ] Character class Matches any character in the brackets. For example,
[abc] matches a, b, or c.
[^ abc ] Negated character class Matches a single character that is not contained within
the brackets. For example,
[^abc] matches any character
other than a, b, or c. [^A-Z] matches any single
character that is not an uppercase letter.
[ a - c ] Character range class Matches any character in the range. [a-z] matches any
lowercase letter. You can mix characters and ranges:
[abcq-z] matches a, b, c, q, r, s, t, u, v, w, x, y, z, and so
does [ a-cq-z] .
The dash (-) character is literal only if it is the last or the
first character within the brackets:
[abc-] or [-abc] .
“” Quotation marks Preserves trailing or leading spaces in the string. For
example,
“ test” preserves the leading space when it
looks for a match.
^ Caret Specifies the beginning of a line.
\ Escape character When used with a metacharacter, matches a literal
character. For example,
\[ matches the left square
bracket.
char Character When character is not a metacharacter, matches the
literal character.
\r Carriage return Matches a carriage return 0x0d.
\n Newline Matches a new line 0x0a.
\t Tab Matches a tab 0x09.
\f Formfeed Matches a form feed 0x0c.
\x NN Escaped hexadecimal number Matches an ASCII character using hexadecimal (exactly
two digits).
\ NNN Escaped octal number Matches an ASCII character as octal (exactly three
digits). For example, the character 040 represents a
space.
Table 12-3 Regular Expression Metacharacters (continued)
Character Description Notes