The Go Programming Language Exercise 1.4

dup1.txt

aaa
aaa
aaa
aaa
aaa
bbb
ccc

dup2.txt

aaa
ccc
ddd

dup3.txt

ccc
ddd
xxx

dup4.txt

xxx
yyy
yyy
yyy
yyy
yyy
www

Ex14.go

package main

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

func main() {
	// Store the names of the files, and the words and times the owrd has repeated
	// { word: {filename : times}}
	counts := make(map[string]map[string]int)
	files := os.Args[1:]

	if len(files) == 0 {
		countLines2(os.Stdin, counts, "os.Stdin")
	} else {
		for _, arg := range files {
			f, err := os.Open(arg)
			if err != nil {
				fmt.Fprintf(os.Stderr, "dup2: %v\n", err)
			}
			countLines2(f, counts, arg)
			f.Close()
		}
	}

	for line, filenames := range counts {

		// Count the number of files in which a line appears in:
		fileCount := len(filenames)

		// Count total number of appearances
		var total = 0

		fmt.Printf("Found [%s] in [%d] files:\n", line, fileCount)
		for name, count := range filenames {
			fmt.Printf("\t%d appearances in %s\n", count, name)
			total += count
		}
		fmt.Printf("\t->Total appearances: %d\n", total)

	}

}

func countLines2(f *os.File, counts map[string]map[string]int, filename string) {
	input := bufio.NewScanner(f)
	for input.Scan() {
		if counts[input.Text()] == nil {
			counts[input.Text()] = make(map[string]int)
		}
		counts[input.Text()][filename]++
	}
}

output.txt

Found [aaa] in [2] files:
        5 appearances in dup1.txt
        1 appearances in dup2.txt
        ->Total appearances: 6
Found [bbb] in [1] files:
        1 appearances in dup1.txt
        ->Total appearances: 1
Found [ccc] in [3] files:
        1 appearances in dup3.txt
        1 appearances in dup1.txt
        1 appearances in dup2.txt
        ->Total appearances: 3
Found [ddd] in [2] files:
        1 appearances in dup2.txt
        1 appearances in dup3.txt
        ->Total appearances: 2
Found [xxx] in [2] files:
        1 appearances in dup4.txt
        1 appearances in dup3.txt
        ->Total appearances: 2
Found [yyy] in [1] files:
        5 appearances in dup4.txt
        ->Total appearances: 5
Found [www] in [1] files:
        1 appearances in dup4.txt
        ->Total appearances: 1