src/fmt/example_test.go

// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package fmt_test

import (
	"fmt"
	"io"
	"os"
	"strings"
)

// The Errorf function lets us use formatting features
// to create descriptive error messages.
func ExampleErrorf() {
	const name, id = "bueller", 17
	err := fmt.Errorf("user %q (id %d) not found", name, id)
	fmt.Println(err.Error())
	// Output: user "bueller" (id 17) not found
}

func ExampleFscanf() {
	var (
		i int
		b bool
		s string
	)
	r := strings.NewReader("5 true gophers")
	n, err := fmt.Fscanf(r, "%d %t %s", &i, &b, &s)
	if err != nil {
		panic(err)
	}
	fmt.Println(i, b, s)
	fmt.Println(n)
	// Output:
	// 5 true gophers
	// 3
}

func ExampleSprintf() {
	i := 30
	s := "Aug"
	sf := fmt.Sprintf("Today is %d %s", i, s)
	fmt.Println(sf)
	fmt.Println(len(sf))
	// Output:
	// Today is 30 Aug
	// 15
}

func ExamplePrint() {
	n, err := fmt.Print("there", "are", 99, "gophers", "\n")
	if err != nil {
		panic(err)
	}
	fmt.Print(n)
	// Output:
	// thereare99gophers
	// 18
}

func ExamplePrintln() {
	n, err := fmt.Println("there", "are", 99, "gophers")
	if err != nil {
		panic(err)
	}
	fmt.Print(n)
	// Output:
	// there are 99 gophers
	// 21
}

func ExampleSprintln() {
	s := "Aug"
	sl := fmt.Sprintln("Today is 30", s)
	fmt.Printf("%q", sl)
	// Output:
	// "Today is 30 Aug\n"
}

func ExampleFprint() {
	n, err := fmt.Fprint(os.Stdout, "there", "are", 99, "gophers", "\n")
	if err != nil {
		panic(err)
	}
	fmt.Print(n)
	// Output:
	// thereare99gophers
	// 18
}

func ExampleFprintln() {
	n, err := fmt.Fprintln(os.Stdout, "there", "are", 99, "gophers")
	if err != nil {
		panic(err)
	}
	fmt.Print(n)
	// Output:
	// there are 99 gophers
	// 21
}

func ExampleFscanln() {
	s := `dmr 1771 1.61803398875
	ken 271828 3.14159`
	r := strings.NewReader(s)
	var a string
	var b int
	var c float64
	for {
		n, err := fmt.Fscanln(r, &a, &b, &c)
		if err == io.EOF {
			break
		}
		if err != nil {
			panic(err)
		}
		fmt.Printf("%d: %s, %d, %f\n", n, a, b, c)
	}
	// Output:
	// 3: dmr, 1771, 1.618034
	// 3: ken, 271828, 3.141590
}

func ExampleSprint() {
	s := fmt.Sprint("there", "are", "99", "gophers")
	fmt.Println(s)
	fmt.Println(len(s))
	// Output:
	// thereare99gophers
	// 17
}