Wildcard character

Source: Wikipedia, the free encyclopedia.

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]

Telecommunication

In

telecommunications
, a wildcard is a character that may be substituted for any of a defined subset of all possible characters.

  • In
    alphanumeric
    characters.
  • Whether the wildcard character represents a single character or a 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.[2] Algorithms for matching wildcards have been developed in a number of recursive and non-recursive varieties.[3]

File and directory patterns

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

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.

Databases

In

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.

Regular expressions

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.

See also

References

  1. ^ "Using wildcard characters". Microsoft. Archived from the original on 2017-03-24. Retrieved 2018-01-23.
  2. ^ "What is a wildcard?". Computer Hope. Archived from the original on 2016-11-21. Retrieved 2016-11-21.
  3. ^ Cantatore, Alessandro (Apr 25, 2003). "Wildcard matching algorithms". Archived from the original on Oct 14, 2023.

External links