go聖經裏有一段查找重複的行的代碼,發現輸入無反應不會打印重複行數據

// Dup1 prints the text of each line that appears more than
// once in the standard input, preceded by its count.
package main

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

func main() {
    counts := make(map[string]int)
    input := bufio.NewScanner(os.Stdin)
    for input.Scan() {
        counts[input.Text()]++
    }
    if input.Err() != nil{
        fmt.Print("err")
    }    
    // NOTE: ignoring potential errors from input.Err()
    for line, n := range counts {
        if n > 1 {
            fmt.Printf("%d\t%s\n", n, line)
        }
    }
}

其實是input.Scan() 這個循環裏面沒有跳出，程序會一直監聽輸入信息，只要加個中斷跳出就非常明白了：

// Dup1 prints the text of each line that appears more than
// once in the standard input, preceded by its count.
package main

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

func main() {
    counts := make(map[string]int)
    input := bufio.NewScanner(os.Stdin)
    for input.Scan() {
        // 控制循環退出
        if input.Text() == "end" { break }
        counts[input.Text()]++
    }
    if input.Err() != nil{
        fmt.Print("err")
    }
    // NOTE: ignoring potential errors from input.Err()
    for line, n := range counts {
        if n > 1 {
            fmt.Printf("%d\t%s\n", n, line)
        }
    }
}

再次輸入

go run ch1/dup1/main.go 
a
a  
b
b
c
end

輸出

2       a
2       b