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