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