How deeply does Go in Action, Second Edition cover fmt.Fprintf?

Explains the destination distinction from fmt.Printf and demonstrates one formatted write, stopping short of deeper formatting details.

Fmt.Fprintf

As explained in Go in Action, Second Edition

fmt.Fprintf is a Go standard-library function that formats text according to a format string and writes it to an io.Writer.

fmt.Fprintf formats text from a format string and writes the result to any io.Writer. Unlike fmt.Printf, it does not require standard output, so the same output logic can target files, buffers, screens, or network connections. section 10.3

This decouples formatting from the destination. A process can accept an io.Writer and send status or error messages wherever the caller chooses, supporting flexible CLI tools and logging systems. section 10.3

Writing a status message

Set writer to os.Stdout or another io.Writer, then call fmt.Fprintf(writer, "Output written to: %s\n", outputFile). The same call can write to a file, buffer, or other supported destination. section 10.3

How Go in Action, Second Edition covers it

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Related concepts

io.Writeruses · io.Writer is a Go interface whose Write method accepts a byte sequence and returns the number of bytes written and any error.
http.ResponseWriteruses · http.ResponseWriter is the Go interface through which an HTTP handler constructs a response by writing its headers, status, and body.
testing.T.Runused by · testing.T.Run is a Go testing method that creates and executes a named subtest and reports its result to the parent test.

This explainer was generated by Manning's knowledge graph from the text of Go in Action, Second Edition. The section links point to the parts of the book it draws on.