# 08.5.2 逐词读取文本文件

本节中展示的技术将通过`byWord.go`文件演示，它由四部分组成。正如你在`Go`代码中看到的，分隔一行中的单词可能比较棘手。程序的第一部分如下：

```go
package main

import (
    "bufio"
    "flag"
    "fmt"
    "io"
    "os"
    "regexp"
)
```

`byWord.go`的第二部分代码如下：

```go
func wordByWord(file string) error {
    var err error
    f, err := os.Open(file)
    if err != nil {
        return err
    }
    defer f.Close()

    r := bufio.NewReader(f)
    for {
        line, err := r.ReadString('\n')
        if err == io.EOF {
            break
        } else if err != nil {
            fmt.Printf("error reading file %s", err)
            return err
        }
```

`wordByWord()`函数的这部分代码和`byLine.go`程序的`lineByLine()`函数一样。

`byWord.go`第三部分代码如下：

```go
        r := regexp.MustCompile("[^\\s]+")
          words := r.FindAllString(line, -1)
          for i := 0; i < len(words); i++ {
              fmt.Printf(words[i])
          }
    }
    return nil
}
```

`wordByWord()`函数的剩余代码是全新的，并使用正则表达式对输入的每行进行单词分割。正则表达式`regexp.MustCompile("[^\\s]+")`使用空格分割单词。

`byWord.go`的最后一部分代码如下：

```go
func main() {
    flag.Parse()
    if len(flag.Args()) == 0 {
        fmt.Printf("usage: byWord <file1> [<file2> ...]\n")
        return
    }

    for _, file := range flag.Args() {
        err := wordByWord(file)
        if err != nil {
            fmt.Println(err)
        }
    }
}
```

执行`byWord.go`会产生如下的输出：

```
$ go run byWord.go /tmp/adobegc.log
01/08/18
20:25:09:669
|
[INFO]
```

可以使用`wc(1)`验证`byWord.go`的正确性：

```
$ go run byWord.go /tmp/adobegc.log | wc
    91591     91591     559005
$ wc /tmp/adobegc.log
    4831      91591     583454     /tmp/adobegc.log
```

如你所见，`wc(1)`计算所得的单词数和`byWord.go`一致。


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