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      1 // Copyright 2013 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 package bufio_test
      6 
      7 import (
      8 	"bufio"
      9 	"fmt"
     10 	"os"
     11 	"strconv"
     12 	"strings"
     13 )
     14 
     15 func ExampleWriter() {
     16 	w := bufio.NewWriter(os.Stdout)
     17 	fmt.Fprint(w, "Hello, ")
     18 	fmt.Fprint(w, "world!")
     19 	w.Flush() // Don't forget to flush!
     20 	// Output: Hello, world!
     21 }
     22 
     23 // The simplest use of a Scanner, to read standard input as a set of lines.
     24 func ExampleScanner_lines() {
     25 	scanner := bufio.NewScanner(os.Stdin)
     26 	for scanner.Scan() {
     27 		fmt.Println(scanner.Text()) // Println will add back the final '\n'
     28 	}
     29 	if err := scanner.Err(); err != nil {
     30 		fmt.Fprintln(os.Stderr, "reading standard input:", err)
     31 	}
     32 }
     33 
     34 // Use a Scanner to implement a simple word-count utility by scanning the
     35 // input as a sequence of space-delimited tokens.
     36 func ExampleScanner_words() {
     37 	// An artificial input source.
     38 	const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n"
     39 	scanner := bufio.NewScanner(strings.NewReader(input))
     40 	// Set the split function for the scanning operation.
     41 	scanner.Split(bufio.ScanWords)
     42 	// Count the words.
     43 	count := 0
     44 	for scanner.Scan() {
     45 		count++
     46 	}
     47 	if err := scanner.Err(); err != nil {
     48 		fmt.Fprintln(os.Stderr, "reading input:", err)
     49 	}
     50 	fmt.Printf("%d\n", count)
     51 	// Output: 15
     52 }
     53 
     54 // Use a Scanner with a custom split function (built by wrapping ScanWords) to validate
     55 // 32-bit decimal input.
     56 func ExampleScanner_custom() {
     57 	// An artificial input source.
     58 	const input = "1234 5678 1234567901234567890"
     59 	scanner := bufio.NewScanner(strings.NewReader(input))
     60 	// Create a custom split function by wrapping the existing ScanWords function.
     61 	split := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
     62 		advance, token, err = bufio.ScanWords(data, atEOF)
     63 		if err == nil && token != nil {
     64 			_, err = strconv.ParseInt(string(token), 10, 32)
     65 		}
     66 		return
     67 	}
     68 	// Set the split function for the scanning operation.
     69 	scanner.Split(split)
     70 	// Validate the input
     71 	for scanner.Scan() {
     72 		fmt.Printf("%s\n", scanner.Text())
     73 	}
     74 
     75 	if err := scanner.Err(); err != nil {
     76 		fmt.Printf("Invalid input: %s", err)
     77 	}
     78 	// Output:
     79 	// 1234
     80 	// 5678
     81 	// Invalid input: strconv.ParseInt: parsing "1234567901234567890": value out of range
     82 }
     83