Io.Writer
io.Writer is a Go interface whose Write method accepts a byte sequence and returns the number of bytes written and any error.
Go by Example
io.Writer is a Go interface whose Write method accepts a byte sequence and returns the number of bytes written and an error.
- How it is used
- Decouples command-line output from global streams so production code and tests can supply different destinations.
- How deep it goes
- Defines Write’s byte-slice contract and explains partial writes, caller-managed memory, and pointer-based Builder satisfaction.
- Examples
- Uses stdout and stderr injection, strings.Builder output capture, FlagSet.SetOutput, io.Discard, and a byte-counting custom Writer exercise.
- What you can do after
- Apply it via standard-library Writers to make command-line output configurable and directly testable.
Go in Action, Second Edition
io.Writer is the Go interface for writing byte data to a destination.
- How it is used
- Uses io.Writer to build flexible I/O and CLI code that targets files, screens, buffers, network connections, or other destinations.
- How deep it goes
- Explains interface-based destination selection, formatted output, and composition, but stops short of detailing the Writer method signature.
- Examples
- Demonstrates file and screen output, fmt.Fprintf status messages, a JSON/XML conversion CLI, and simultaneous output with io.MultiWriter.
- What you can do after
- Apply io.Writer with fmt.Fprintf to route formatted output through interchangeable destinations.
Related concepts
- os.Fileimplemented by · os.File is a Go standard-library type representing an open file or other operating-system file handle and providing associated file operations.
- write operationhas part · A write operation transfers data to a destination or changes stored data or other state.
- contractkind of · An API contract is a specification of the operations, data, and behavioral expectations that govern interactions between software components.
- io.Copyused by · io.Copy is a Go standard-library function that copies bytes from an io.Reader to an io.Writer until input is exhausted or an error occurs.
- http.ResponseWriterincludes · http.ResponseWriter is the Go interface through which an HTTP handler constructs a response by writing its headers, status, and body.
- natural language interfacekind of · A natural language interface enables interaction with a system through human-language text or speech.
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