Wildcard character

Wildcard ( Wildcard from the English, a playing card poker ), Joker (after Joker, a playing card ) or wildcards designated computer area a placeholder for other characters. This concept is referred to frequently as globbing.

More details

Many command line interpreter and other programs allow the use of such placeholder to address, for example, groups of files that have similar names. Also search functions in text editors familiar with such a placeholder.

Placeholder often used are:

• The question mark (?) ( more common than common abbreviation in library catalogs ) or the underscore ( _) for exactly one character
• The asterisk ( *) and the percent sign (%) for any number (including zero) characters
• The hash mark ( #) to a numeric value.

• A search of finds all strings that end in and before have any character; Examples would be home, house, mouse, and get out. The search for a * provides other hand out also about.

Some programs, such as POSIX -compliant UNIX shells, programming and expand the wildcard principle on regular expressions by allowing more than one character at one point: these brackets are used. So is about [ HMr ] from for home, mouse in and out. Also letter areas can be given in the brackets: [a- zA -Z] * will search for all files whose names consist only of the 26 letters from A to Z ( in large and small).

The database language SQL uses the underscore (_ ) as a wildcard for one character and the percent sign (% ) as a wildcard for any number of characters.