Wildcard
A wildcard is a pattern symbol or expression that matches unspecified or variable characters, values, names, types, or path segments.
F# in Action: A Revised Edition of Get Programming with F#
A wildcard is a pattern or placeholder that matches a value without binding or using its contents.
- How it is used
- Discards unwanted tuple elements and supplies fallback branches in F# pattern matches.
- How deep it goes
- Explains tuple discards, ordered fallback matching, compiler warnings, and maintenance consequences for discriminated unions.
- Examples
- Uses name-and-age tuple deconstruction, loan-decision rules, SMS contact methods, and instrument matching.
- What you can do after
- Apply it to discard unneeded values and choose explicit or fallback pattern-match cases deliberately.
Read how F# in Action: A Revised Edition of Get Programming with F# explains wildcard →
Go in Practice, Second Edition
A wildcard is a route-pattern element that matches a variable portion of a URL path.
- How it is used
- Routes requests whose URL paths contain variable values without registering every exact path.
- How deep it goes
- Works through ServeMux patterns and PathValue retrieval, then points to regular expressions for more complex matching.
- Examples
- Shows `/goodbye/` alongside `GET /goodbye/{name}` and contrasts PathValue with manual URL-path splitting.
- What you can do after
- Apply it via Go’s ServeMux to route a variable path and read its value in a handler.
MongoDB 8.0 in Action, Third Edition
A wildcard expression specifies a text-search pattern containing placeholder characters that match variable text.
- How it is used
- Finds records whose text fields fit a pattern despite unknown characters or incomplete information.
- How deep it goes
- Defines both placeholders and walks through an Atlas Search pipeline; briefly notes indexed-term matching without detailing its internals.
- Examples
- Uses a `business_name` query for `*L?CE*` and shows matching inspection records ordered by search score.
- What you can do after
- Apply it via Atlas Search to retrieve pattern-matching records and shape the returned results with aggregation stages.
Read how MongoDB 8.0 in Action, Third Edition explains wildcard →
Elasticsearch in Action, Second Edition
A wildcard is a pattern symbol representing one or more variable characters when selecting index names or matching terms.
- How it is used
- Selects groups of index names and matches terms with missing, leading, trailing, or internal characters.
- How deep it goes
- Explains both wildcard operators, analyzed versus keyword fields, and expensive-query concerns without detailing execution internals.
- Examples
- Uses ca*, mov*, stu*, god*, g*d, and go?ather for index selection and movie-title matching.
- What you can do after
- Apply wildcard patterns through Elasticsearch REST requests while accounting for field analysis and query cost.
Read how Elasticsearch in Action, Second Edition explains wildcard →
Learn SQL in a Month of Lunches
A percent wildcard (%) is an SQL pattern-matching character that matches any sequence of characters, including an empty string.
- How it is used
- Filters text columns by matching flexible patterns such as prefixes, suffixes, or contained character sequences.
- How deep it goes
- Explains percent matching, LIKE syntax, placement patterns, and the distinction from single-character underscore matching.
- Examples
- Demonstrates author-name searches for prefixes, suffixes, bounded patterns, and contained text.
- What you can do after
- Apply it via SQL LIKE to search text columns for flexible character patterns.
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Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS
A wildcard is a pattern-matching character or expression that represents one or more possible characters in a name or search.
- How it is used
- Supports discovering commands and supplying partial names wherever PowerShell parameters accept wildcard values.
- How deep it goes
- Demonstrates wildcard searches and partial paths but stops short of detailing pattern syntax or matching internals.
- Examples
- Uses Help *event*, Help *object*, event-command results, Help Register-ObjectEvent, and the partial path Down*.
- What you can do after
- Apply wildcards via Help and Get-Command to discover likely commands, then inspect their examples and full help.
API Design Patterns
A wildcard is a symbol or placeholder that stands for an unspecified value or set of values in a pattern or identifier.
- How it is used
- Uses the hyphen to route batch operations across resources belonging to multiple parents.
- How deep it goes
- Defines routing, conflict rejection, atomicity, and storage-distribution trade-offs, but does not develop wildcard syntax beyond parent identifiers.
- Examples
- Demonstrates /users/-/emails:archive and /chatRooms/-/messages:batchCreate for operations spanning multiple parents.
- What you can do after
- Apply it via HTTP API routes for multi-parent batch creation, retrieval, and archival while rejecting ambiguity.
Learn Haskell by Example
A wildcard pattern is a pattern that matches any input without binding that input to an identifier.
- How it is used
- Uses wildcard patterns to discard irrelevant inputs and provide catch-all cases in pattern matching.
- How deep it goes
- Defines wildcard matching, demonstrates discarded bindings, and notes exhaustive final patterns without developing error-safe fallbacks.
- Examples
- Uses filename-argument parsing and recursive line numbering as concrete wildcard examples.
- What you can do after
- Apply it via pattern matching to ignore values, simplify unused arguments, and close remaining pattern cases.
Related concepts
- regular expressioncontrasts with · A formal pattern notation that describes sets of strings and enables text to be matched, searched, extracted, or transformed.
- comparisonused by · A comparison is a language operation that tests a relationship between values or expressions, such as equality or ordering, and produces a result.
- routinguses · Routing is the selection of a path, destination, or processing component to direct an item, request, or flow toward an intended endpoint.
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