[:
... :]
)
If the syntax bit RE_CHARACTER_CLASSES
is set, then Regex
recognizes character class expressions inside lists. A character
class expression matches one character from a given class. You form a
character class expression by putting a character class name between an
open-character-class operator (represented by `[:') and a
close-character-class operator (represented by `:]'). The
character class names and their meanings are:
alnum
alpha
blank
cntrl
digit
graph
print
except omits space
lower
print
punct
space
upper
xdigit
0
--9
, a
--f
, A
--F
These correspond to the definitions in the C library's `<ctype.h>'
facility. For example, `[:alpha:]' corresponds to the standard
facility isalpha
. Regex recognizes character class expressions
only inside of lists; so `[[:alpha:]]' matches any letter, but
`[:alpha:]' outside of a bracket expression and not followed by a
repetition operator matches just itself.
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