mirror of
https://github.com/gopl-zh/gopl-zh.github.com.git
synced 2024-11-10 08:23:42 +00:00
49 lines
931 B
Go
49 lines
931 B
Go
|
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
|
||
|
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
||
|
|
|
||
|
|
// See page 10.
|
||
|
|
//!+
|
||
|
|
|
||
|
|
// Dup2 prints the count and text of lines that appear more than once
|
||
|
|
// in the input. It reads from stdin or from a list of named files.
|
||
|
|
package main
|
||
|
|
|
||
|
|
import (
|
||
|
|
"bufio"
|
||
|
|
"fmt"
|
||
|
|
"os"
|
||
|
|
)
|
||
|
|
|
||
|
|
func main() {
|
||
|
|
counts := make(map[string]int)
|
||
|
|
files := os.Args[1:]
|
||
|
|
if len(files) == 0 {
|
||
|
|
countLines(os.Stdin, counts)
|
||
|
|
} else {
|
||
|
|
for _, arg := range files {
|
||
|
|
f, err := os.Open(arg)
|
||
|
|
if err != nil {
|
||
|
|
fmt.Fprintf(os.Stderr, "dup2: %v\n", err)
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
countLines(f, counts)
|
||
|
|
f.Close()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
for line, n := range counts {
|
||
|
|
if n > 1 {
|
||
|
|
fmt.Printf("%d\t%s\n", n, line)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func countLines(f *os.File, counts map[string]int) {
|
||
|
|
input := bufio.NewScanner(f)
|
||
|
|
for input.Scan() {
|
||
|
|
counts[input.Text()]++
|
||
|
|
}
|
||
|
|
// NOTE: ignoring potential errors from input.Err()
|
||
|
|
}
|
||
|
|
|
||
|
|
//!-
|