The term wildcard character has several meanings.
- In high-frequency (HF) radio automatic link establishment, the wildcard character "?" may be substituted for any one of the 36 characters, "A" through "Z" and "0" through "9."
- Whether the wildcard character represents a single character or a string of characters must be specified.
File and directory patterns
In Unix-like and DOS operating systems, the question mark ("?") matches exactly one character; in DOS, it will also match missing (zero) trailing characters. For example, in DOS, the pattern
123??? will match
12313, but not
In Unix shells and Windows PowerShell, ranges of characters enclosed in square brackets ("[" and "]") match a single character within the range; for example,
[A-Za-z] matches any single uppercase or lowercase letter. Unix shells allow negation of the specified character set by using a leading "!" (e.g.,
foo.[!ch], which will match names like
foo.o). In shells that interpret "!" as a history substitution, a leading "^" can be used instead of "!" to negate the character set.
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 (^) matches only a character not specified within the brackets. In Microsoft Access, wildcard characters can be used in "LIKE" expressions; the asterisk sign (*) matches zero or more characters, and the question mark (?) matches a single character.
In regular expressions, the period (".", also called "dot") is the wildcard pattern character that matches a single character. Combined with the asterisk operator (.*) it will match any number of characters.
- 12px This article incorporates public domain material from the General Services Administration document [[[:Template:If empty]] "Template:If empty"] (in support of MIL-STD-188).