Editing Wildcard character

{{short description|Character used to substitute for any other character/s in a string}}
{{for|wildcard characters within the Wikipedia search engine|Help:Wildcard|selfref=y}}
{{one source|date=May 2016}}

In [[software]], a '''wildcard character''' is a kind of '''placeholder''' represented by a single [[character (computing)|character]], such as an [[asterisk]] ({{code|*}}), 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.<ref>{{Cite web|url=https://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/find_c_search_wildcard.mspx?mfr=true|title=Using wildcard characters |website=Microsoft |access-date=2018-01-23|url-status=dead |archive-url=https://web.archive.org/web/20170324204434/http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/find_c_search_wildcard.mspx?mfr=true|archive-date=2017-03-24}}</ref>

==Telecommunication==
In [[telecommunications]], a wildcard is a character that may be substituted for any of a defined subset of all possible characters.

* In [[high-frequency]] (HF) [[radio]] [[automatic link establishment]], the wildcard character {{code|?}} may be substituted for any one of the 36 upper-case [[alphanumeric]] characters.
* Whether the wildcard character represents a single character or a [[String (computer science)|string]] of characters must be specified.

==Computing==
In [[computer]] ([[software]]) technology, a wildcard is a symbol used to replace or represent zero or more characters.<ref>{{Cite news|url=http://www.computerhope.com/jargon/w/wildcard.htm|title=What is a wildcard? |website=Computer Hope |access-date=2016-11-21|url-status=live|archive-url=https://web.archive.org/web/20161121171416/http://www.computerhope.com/jargon/w/wildcard.htm|archive-date=2016-11-21}}</ref> [[Matching wildcards|Algorithms for matching wildcards]] have been developed in a number of [[recursion|recursive]] and non-recursive varieties.<ref>{{cite web| last=Cantatore| first=Alessandro| title=Wildcard matching algorithms| date=Apr 25, 2003| url=http://xoomer.virgilio.it/acantato/dev/wildcard/wildmatch.html |url-status=live |archive-url=https://web.archive.org/web/20231014125822/https://xoomer.virgilio.it/acantato/dev/wildcard/wildmatch.html |archive-date= Oct 14, 2023 }}</ref>

===File and directory patterns===
When specifying file names (or paths) in [[CP/M]], [[DOS]], [[Microsoft Windows]], and [[Unix-like]] [[operating system]]s, the [[asterisk]] character ({{code|*}}, also called "star") matches zero or more characters. For example, {{code|doc*}} matches {{code|doc}} and {{code|document}} but not {{code|dodo}}. If files are named with a date stamp, wildcards can be used to match date ranges, such as <code>{{#time:Ym}}*.mp4</code> to select video recordings from {{#time:F}} {{#time:Y}}, to facilitate file operations such as copying and moving.

In Unix-like and DOS operating systems, the [[question mark]] {{code|?}} 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 {{code|123?}} will match {{code|123}} and {{code|1234}}, but not {{code|12345}}.

In [[Unix shell]]s and [[Windows PowerShell]], ranges of characters enclosed in [[square brackets]] ({{code|[}} and {{code|]}}) match a single character within the set; for example, {{code|[A-Za-z]}} matches any single uppercase or lowercase letter. In Unix shells, a leading exclamation mark {{code|!}} negates the set and matches only a character not within the list. In shells that interpret {{code|!}} as a history substitution, a leading caret {{code|^}} can be used instead.

The operation of matching of wildcard patterns to multiple file or path names is referred to as [[glob (programming)|''globbing'']].

===Databases===
In [[SQL]], wildcard characters can be used in LIKE expressions; the [[percent]] sign {{code|%}} matches zero or more characters, and [[underscore]] {{code|_}} a single character. [[Transact-SQL]] also supports [[square brackets]] ({{code|[}} and {{code|]}}) to list sets and ranges of characters to match, a leading caret {{code|^}} negates the set and matches only a character not within the list. In [[Microsoft Access]], the [[asterisk]] sign {{code|*}} matches zero or more characters, the [[question mark]] {{code|?}} matches a single character, the [[number sign]] {{code|#}} matches a single digit (0–9), and square brackets can be used for sets or ranges of characters to match.

===Regular expressions===
In [[regular expression]]s, the [[Full stop|period]] ({{code|.}}, also called "dot") is the wildcard pattern which matches any single character. Followed by the [[Kleene star]] operator, which is denoted as an [[asterisk]] ({{code|*}}), we obtain {{code|.*}}, which will match zero or more arbitrary characters.

==See also==
* [[glob (programming)]]
* [[Pattern matching]]
* [[Query by Example]]
* [[Wild card (cards)]]
* [[Wildcard DNS record]]
* [[wildmat]]

==References==
<references />
*{{FS1037C MS188}}

==External links==
*[http://www.linfo.org/wildcard.html How to Use Wildcards]

[[Category:Computer file formats]]
[[Category:Pattern matching]]