Wildcard character - AbsoluteAstronomy.com

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

s, a wildcard character is a character

Character (computing)

In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....

that may be substituted for any of a defined subset of all possible characters.

In high-frequency (HF) radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

automatic link establishment
Automatic link establishment
Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system, that enables the radio station to make contact, or initiate a circuit, between...

, 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
String (computer science)
In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....

of characters must be specified.

Computing

In computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

(software) technology, a wildcard character can be used to substitute for any other character or characters in a string.

Files and directories

When specifying file names (or paths) in CP/M

CP/M

CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...

, DOS

DOS

DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

, Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

and Unix-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

s, the asterisk character ("*")

Asterisk

An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...

substitutes for any zero or more characters, and the question mark ("?")

Question mark

The question mark , is a punctuation mark that replaces the full stop at the end of an interrogative sentence in English and many other languages. The question mark is not used for indirect questions...

substitutes for any one character or less but not more than the amount of question marks. For example 123??? will match 1231 or 12313 but not 1239919991. In Unix shell

Unix shell

A Unix shell is a command-line interpreter or shell that provides a traditional user interface for the Unix operating system and for Unix-like systems...

s and Windows PowerShell

Windows PowerShell

Windows PowerShell is Microsoft's task automation framework, consisting of a command-line shell and associated scripting language built on top of, and integrated with the .NET Framework...

, ranges of characters enclosed in square brackets ("[" and "]") substitute for all the characters in their ranges; for example, [A-Za-z] substitutes for any single capitalized or lowercase letter. Unix shells allow negation of the specified characters within brackets by using a leading "!". Matching wildcard patterns to multiple files or paths is referred to as glob expansion.

Databases

In SQL

SQL

SQL is a programming language designed for managing data in relational database management systems ....

, wildcard characters can be used in "LIKE" expressions; the percent sign (%) matches zero or more characters, and underscore

Underscore

The underscore [ _ ] is a character that originally appeared on the typewriter and was primarily used to underline words...

(_) a single character. Transact-SQL

Transact-SQL

Transact-SQL is Microsoft's and Sybase's proprietary extension to SQL. SQL, often expanded to Structured Query Language, is a standardized computer language that was originally developed by IBM for querying, altering and defining relational databases, using declarative statements...

also supports square brackets ("[" and "]") to list sets and ranges of characters to match, a leading ^ matches only a character not specified within the brackets. In Microsoft Access

Microsoft Access

Microsoft Office Access, previously known as Microsoft Access, is a relational database management system from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software-development tools. It is a member of the Microsoft Office suite of...

, wildcard characters can be used in "LIKE" expressions; the asterisk

Asterisk

An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...

sign (*) matches zero or more characters, and question mark

Question mark

(?) a single character.

In SAP the plus-sign (+) matches exactly one character.

Regular expressions

In regular expression

Regular expression

In computing, a regular expression provides a concise and flexible means for "matching" strings of text, such as particular characters, words, or patterns of characters. Abbreviations for "regular expression" include "regex" and "regexp"...

s, the period

Full stop

A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people...

(.) is the wildcard character for a single character. Combined with the asterisk

Asterisk

An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...

operator (.*) it will match any number of characters.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Telecommunication

Computing

Files and directories

Databases

Regular expressions

See also

External links