如何打印通过stdin引入的行数？

Question

I have the following program that I want to show how many times a specific introduced line appears from stdin:

package main

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

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

When I run the program it allows me to enter strings, but even when I press enter I don't get any feedback.

What am I missing here? I believe it gets stuked in the first for.

Answer 1

Try this - save the following text in /tmp/input.txt or other local file:

Line A
Line B
Line B
Line A
Line C
Line B

Now pipe the contents of that file as standard input to your program - for example in /tmp/q.go: cat /tmp/input.txt | go run /tmp/q.go The output should be:

$ cat /tmp/input.txt | go run /tmp/q.go
2   Line A
3   Line B