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// Copyright 2013 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 bufio_test
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
func ExampleWriter() {
w := bufio.NewWriter(os.Stdout)
fmt.Fprint(w, "Hello, ")
fmt.Fprint(w, "world!")
w.Flush() // Don't forget to flush!
// Output: Hello, world!
}
// The simplest use of a Scanner, to read standard input as a set of lines.
func ExampleScanner_lines() {
scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
fmt.Println(scanner.Text()) // Println will add back the final '\n'
}
if err := scanner.Err(); err != nil {
fmt.Fprintln(os.Stderr, "reading standard input:", err)
}
}
// Return the most recent call to Scan as a []byte.
func ExampleScanner_Bytes() {
scanner := bufio.NewScanner(strings.NewReader("gopher"))
for scanner.Scan() {
fmt.Println(len(scanner.Bytes()) == 6)
}
if err := scanner.Err(); err != nil {
fmt.Fprintln(os.Stderr, "shouldn't see an error scanning a string")
}
// Output:
// true
}
// Use a Scanner to implement a simple word-count utility by scanning the
// input as a sequence of space-delimited tokens.
func ExampleScanner_words() {
// An artificial input source.
const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n"
scanner := bufio.NewScanner(strings.NewReader(input))
// Set the split function for the scanning operation.
scanner.Split(bufio.ScanWords)
// Count the words.
count := 0
for scanner.Scan() {
count++
}
if err := scanner.Err(); err != nil {
fmt.Fprintln(os.Stderr, "reading input:", err)
}
fmt.Printf("%d\n", count)
// Output: 15
}
// Use a Scanner with a custom split function (built by wrapping ScanWords) to validate
// 32-bit decimal input.
func ExampleScanner_custom() {
// An artificial input source.
const input = "1234 5678 1234567901234567890"
scanner := bufio.NewScanner(strings.NewReader(input))
// Create a custom split function by wrapping the existing ScanWords function.
split := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
advance, token, err = bufio.ScanWords(data, atEOF)
if err == nil && token != nil {
_, err = strconv.ParseInt(string(token), 10, 32)
}
return
}
// Set the split function for the scanning operation.
scanner.Split(split)
// Validate the input
for scanner.Scan() {
fmt.Printf("%s\n", scanner.Text())
}
if err := scanner.Err(); err != nil {
fmt.Printf("Invalid input: %s", err)
}
// Output:
// 1234
// 5678
// Invalid input: strconv.ParseInt: parsing "1234567901234567890": value out of range
}
// Use a Scanner with a custom split function to parse a comma-separated
// list with an empty final value.
func ExampleScanner_emptyFinalToken() {
// Comma-separated list; last entry is empty.
const input = "1,2,3,4,"
scanner := bufio.NewScanner(strings.NewReader(input))
// Define a split function that separates on commas.
onComma := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
for i := 0; i < len(data); i++ {
if data[i] == ',' {
return i + 1, data[:i], nil
}
}
if !atEOF {
return 0, nil, nil
}
// There is one final token to be delivered, which may be the empty string.
// Returning bufio.ErrFinalToken here tells Scan there are no more tokens after this
// but does not trigger an error to be returned from Scan itself.
return 0, data, bufio.ErrFinalToken
}
scanner.Split(onComma)
// Scan.
for scanner.Scan() {
fmt.Printf("%q ", scanner.Text())
}
if err := scanner.Err(); err != nil {
fmt.Fprintln(os.Stderr, "reading input:", err)
}
// Output: "1" "2" "3" "4" ""
}
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