Posix Character Classes - Cisco CS-MARS-20-K9 - Security MARS 20 User Manual

Appendix B Regular Expression Reference
The minus (hyphen) character can be used to specify a range of characters in a character class. For
example, [d-m] matches any letter between d and m, inclusive. If a minus character is required in a class,
it must be escaped with a backslash or appear in a position where it cannot be interpreted as indicating
a range, typically as the first or last character in the class.
It is not possible to have the literal character "]" as the end character of a range. A pattern such as [W-]46]
is interpreted as a class of two characters ("W" and "-") followed by a literal string "46]", so it would
match "W46]" or "-46]". However, if the "]" is escaped with a backslash it is interpreted as the end of
range, so [W-\]46] is interpreted as a class containing a range followed by two other characters. The octal
or hexadecimal representation of "]" can also be used to end a range.
Ranges operate in the collating sequence of character values. They can also be used for characters
specified numerically, for example [\000-\037]. In UTF-8 mode, ranges can include characters whose
values are greater than 255, for example [\x{100}-\x{2ff}].
If a range that includes letters is used when caseless matching is set, it matches the letters in either case.
For example, [W-c] is equivalent to [][\\^_`wxyzabc], matched caselessly, and in non-UTF-8 mode, if
character tables for the "fr_FR" locale are in use, [\xc8-\xcb] matches accented E characters in both
cases. In UTF-8 mode, PCRE supports the concept of case for characters with values greater than 128
only when it is compiled with Unicode property support.
The character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear in a character class, and add the
characters that they match to the class. For example, [\dABCDEF] matches any hexadecimal digit. A
circumflex can conveniently be used with the upper case character types to specify a more restricted set
of characters than the matching lower case type. For example, the class [^\W_] matches any letter or
digit, but not underscore.
The only metacharacters that are recognized in character classes are backslash, hyphen (only where it
can be interpreted as specifying a range), circumflex (only at the start), opening square bracket (only
when it can be interpreted as introducing a POSIX class name - see the next section), and the terminating
closing square bracket. However, escaping other non-alphanumeric characters does no harm.

Posix Character Classes

Perl supports the POSIX notation for character classes. This uses names enclosed by [: and :] within the
enclosing square brackets. PCRE also supports this notation. For example,
matches "0", "1", any alphabetic character, or "%". The supported class names are
78-17020-01
[01[:alpha:]%]
alnum letters and digits
alpha letters
ascii character codes 0 - 127
blank space or tab only
cntrl control characters
digit decimal digits (same as \d)
graph printing characters, excluding space
lower lower case letters
print printing characters, including space
punct printing characters, excluding letters and digits
space white space (not quite the same as \s)
upper upper case letters
word "word" characters (same as \w)
xdigit hexadecimal digits
User Guide for Cisco Security MARS Local Controller
Posix Character Classes
B-9