This article relies largely or entirely on a
single source. (May 2016) |
In
software, a wildcard character is a kind of placeholder represented by a single
character, such as an
asterisk (*
), which can be interpreted as a number of literal characters or an
empty string. It is often used in file searches so the full name need not be typed.
[1]
In telecommunications, a wildcard is a character that may be substituted for any of a defined subset of all possible characters.
?
may be substituted for any one of the 36 upper-case
alphanumeric characters.In computer ( software) technology, a wildcard is a symbol used to replace or represent zero or more characters. [2] Algorithms for matching wildcards have been developed in a number of recursive and non-recursive varieties. [3]
When specifying file names (or paths) in
CP/M,
DOS,
Microsoft Windows, and
Unix-like
operating systems, the
asterisk character (*
, also called "star") matches zero or more characters. For example, doc*
matches doc
and document
but not dodo
. If files are named with a date stamp, wildcards can be used to match date ranges, such as 202403*.mp4
to select video recordings from March 2024, to facilitate file operations such as copying and moving.
In Unix-like and DOS operating systems, the
question mark ?
matches exactly one character. In DOS, if the question mark is placed at the end of the word, it will also match missing (zero) trailing characters; for example, the pattern 123?
will match 123
and 1234
, but not 12345
.
In
Unix shells and
Windows PowerShell, ranges of characters enclosed in
square brackets ( and
) match a single character within the set; for example,
[A-Za-z]
matches any single uppercase or lowercase letter. In Unix shells, a leading exclamation mark !
negates the set and matches only a character not within the list. In shells that interpret !
as a history substitution, a leading caret ^
can be used instead.
The operation of matching of wildcard patterns to multiple file or path names is referred to as globbing.
In
SQL, wildcard characters can be used in
LIKE expressions; the
percent sign %
matches zero or more characters, and
underscore _
a single character.
Transact-SQL also supports
square brackets ( and
) to list sets and ranges of characters to match, a leading caret
^
negates the set and matches only a character not within the list. In
Microsoft Access, the
asterisk sign *
matches zero or more characters, the
question mark ?
matches a single character, the
number sign #
matches a single digit (0–9), and square brackets can be used for sets or ranges of characters to match.
In
regular expressions, the
period (.
, also called "dot") is the wildcard pattern which matches any single character. Combined with the
asterisk operator .*
it will match any number of any characters.
In this case, the asterisk is also known as the Kleene star.