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Common Policy Objects
Each character class designates a set of characters equivalent to the corresponding
standard C isXXX function. For example, [:alpha:] designates those characters for which
isalpha() returns true (example: any alphabetic character). Character classes must be
within bracket expression.
CHARACTER CLASS DESCRIPTION
[:alpha:] Alphabetic characters
[:digit:] Digits
[:alnum:] Alphabetic characters and numeric characters
[:cntrl:] Control character
[:blank:] Space and tab
[:space:] All white space characters
[:graph:] Non-blank (not spaces, control characters, or the
like)
[:print:] Like [:graph:], but includes the space character
[:punct:] Punctuation characters
[:lower:] Lowercase alphabetic
[:upper:] Uppercase alphabetic
[:xdigit:] Digits allowed in a hexadecimal number (0-9a-fA-F)
For a case-insensitive expression, [:lower:] and [:upper:] are equivalent to [:alpha:].
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