Go行過濾器範例

線過濾器是一種常見型別的程式，它讀取stdin上的輸入，處理它，然後將一些派生結果列印到stdout。grep和sed是常用的行過濾器。

這裡是一個範例行過濾器，將寫入所有輸入文字轉換為大寫。可以使用此模式來編寫自己的Go行過濾器。

所有的範例程式碼，都放在 F:\worksp\golang 目錄下。安裝Go程式設計環境請參考：/2/23/798.html

line-filters.go的完整程式碼如下所示 -

package main

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

func main() {

    // Wrapping the unbuffered `os.Stdin` with a buffered
    // scanner gives us a convenient `Scan` method that
    // advances the scanner to the next token; which is
    // the next line in the default scanner.
    scanner := bufio.NewScanner(os.Stdin)

    for scanner.Scan() {
        // `Text` returns the current token, here the next line,
        // from the input.
        ucl := strings.ToUpper(scanner.Text())

        // Write out the uppercased line.
        fmt.Println(ucl)
    }

    // Check for errors during `Scan`. End of file is
    // expected and not reported by `Scan` as an error.
    if err := scanner.Err(); err != nil {
        fmt.Fprintln(os.Stderr, "error:", err)
        os.Exit(1)
    }
}

執行上面程式碼，將得到以下輸出結果 -

F:\worksp\golang>go run line-filters.go
this is a Line filters demo by tw511.com
THIS IS A LINE FILTERS DEMO BY TW511.COM
yes
YES
No
NO