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 84 // Use a Scanner with a custom split function to parse a comma-separated 85 // list with an empty final value. 86 func ExampleScanner_emptyFinalToken() { 87 // Comma-separated list; last entry is empty. 88 const input = "1,2,3,4," 89 scanner := bufio.NewScanner(strings.NewReader(input)) 90 // Define a split function that separates on commas. 91 onComma := func(data []byte, atEOF bool) (advance int, token []byte, err error) { 92 for i := 0; i < len(data); i++ { 93 if data[i] == ',' { 94 return i + 1, data[:i], nil 95 } 96 } 97 // There is one final token to be delivered, which may be the empty string. 98 // Returning bufio.ErrFinalToken here tells Scan there are no more tokens after this 99 // but does not trigger an error to be returned from Scan itself. 100 return 0, data, bufio.ErrFinalToken 101 } 102 scanner.Split(onComma) 103 // Scan. 104 for scanner.Scan() { 105 fmt.Printf("%q ", scanner.Text()) 106 } 107 if err := scanner.Err(); err != nil { 108 fmt.Fprintln(os.Stderr, "reading input:", err) 109 } 110 // Output: "1" "2" "3" "4" "" 111 } 112
