bash: Pattern Matching
3.5.8.1 Pattern Matching
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Any character that appears in a pattern, other than the special pattern
characters described below, matches itself. The NUL character may not
occur in a pattern. A backslash escapes the following character; the
escaping backslash is discarded when matching. The special pattern
characters must be quoted if they are to be matched literally.
The special pattern characters have the following meanings:
'*'
Matches any string, including the null string. When the 'globstar'
shell option is enabled, and '*' is used in a filename expansion
context, two adjacent '*'s used as a single pattern will match all
files and zero or more directories and subdirectories. If followed
by a '/', two adjacent '*'s will match only directories and
subdirectories.
'?'
Matches any single character.
'[...]'
Matches any one of the enclosed characters. A pair of characters
separated by a hyphen denotes a RANGE EXPRESSION; any character
that falls between those two characters, inclusive, using the
current locale's collating sequence and character set, is matched.
If the first character following the '[' is a '!' or a '^' then any
character not enclosed is matched. A '-' may be matched by
including it as the first or last character in the set. A ']' may
be matched by including it as the first character in the set. The
sorting order of characters in range expressions is determined by
the current locale and the values of the 'LC_COLLATE' and 'LC_ALL'
shell variables, if set.
For example, in the default C locale, '[a-dx-z]' is equivalent to
'[abcdxyz]'. Many locales sort characters in dictionary order, and
in these locales '[a-dx-z]' is typically not equivalent to
'[abcdxyz]'; it might be equivalent to '[aBbCcDdxXyYz]', for
example. To obtain the traditional interpretation of ranges in
bracket expressions, you can force the use of the C locale by
setting the 'LC_COLLATE' or 'LC_ALL' environment variable to the
value 'C', or enable the 'globasciiranges' shell option.
Within '[' and ']', CHARACTER CLASSES can be specified using the
syntax '[:'CLASS':]', where CLASS is one of the following classes
defined in the POSIX standard:
alnum alpha ascii blank cntrl digit graph lower
print punct space upper word xdigit
A character class matches any character belonging to that class.
The 'word' character class matches letters, digits, and the
character '_'.
Within '[' and ']', an EQUIVALENCE CLASS can be specified using the
syntax '[='C'=]', which matches all characters with the same
collation weight (as defined by the current locale) as the
character C.
Within '[' and ']', the syntax '[.'SYMBOL'.]' matches the collating
symbol SYMBOL.
If the 'extglob' shell option is enabled using the 'shopt' builtin,
several extended pattern matching operators are recognized. In the
following description, a PATTERN-LIST is a list of one or more patterns
separated by a '|'. Composite patterns may be formed using one or more
of the following sub-patterns:
'?(PATTERN-LIST)'
Matches zero or one occurrence of the given patterns.
'*(PATTERN-LIST)'
Matches zero or more occurrences of the given patterns.
'+(PATTERN-LIST)'
Matches one or more occurrences of the given patterns.
'@(PATTERN-LIST)'
Matches one of the given patterns.
'!(PATTERN-LIST)'
Matches anything except one of the given patterns.
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