在golang中读取stdin的输入

我有这个代码:

func readTwoLines() {
    reader := bufio.NewReader(os.Stdin)
    line, _ := reader.ReadString('\n')
    fmt.Println(line)
    line, _ = reader.ReadString('\n')
    fmt.Println(line)
}

输入:

hello
bye

输出是:

hello
bye

一切还好.但现在,如果我每行创建一个阅读器:

func readTwoLines() {
  line, _ := bufio.NewReader(os.Stdin).ReadString('\n')
  fmt.Println(line)
  line, err := bufio.NewReader(os.Stdin).ReadString('\n')
  if err != nil {
    fmt.Println(err)
  }    
  fmt.Println(line)
}

EOF

为什么会这样？

1> wasmup..：

---

Scanner

// NewReader returns a new Reader whose buffer has the default size.
func NewReader(rd io.Reader) *Reader {
  return NewReaderSize(rd, defaultBufSize)
}

defaultBufSize = 4096

甚至你的输入包含4000个字节,仍然第二次读取没有任何东西可读.但如果输入的输入超过4096字节,它将起作用.

---

如果ReadString在找到分隔符之前遇到错误,它将返回错误之前读取的数据和错误本身(通常是io.EOF).

它是按设计,见doc:

// ReadString reads until the first occurrence of delim in the input,
// returning a string containing the data up to and including the delimiter.
// If ReadString encounters an error before finding a delimiter,
// it returns the data read before the error and the error itself (often io.EOF).
// ReadString returns err != nil if and only if the returned data does not end in
// delim.
// For simple uses, a Scanner may be more convenient.
func (b *Reader) ReadString(delim byte) (string, error) {
    bytes, err := b.ReadBytes(delim)
    return string(bytes), err
}

---

试试这个:

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    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)
    }
}

跑:

go run m.go 

输出:

hello
bye


in.txt 文件:

hello
bye


我希望这有帮助.