go-examples/go-cat2/main.go

package main

import "fmt"
import "io"
import "log"
import "os"
import "strings"

var err error
var reader io.Reader

const BUFSIZE = 32 * 1024

func openFile(path *string) *os.File {
	f, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatalln(err)
	}
	return f
}

func readMe(r io.Reader) {
	var n int
	buf := make([]byte, BUFSIZE)
	for {
		n, err = r.Read(buf)
		if n == 0 || err == io.EOF {
			break
		}
		if err != nil {
			log.Fatalln("Read error", err)
		}
		fmt.Printf("%s", buf[:n])
	}
}

func main() {
	if len(os.Args) <= 1 {
		var content string
		if _, err := fmt.Scanln(&content); err != nil {
			log.Fatalln(err)
		}
		reader = strings.NewReader(content)
	} else {
		readers := []io.Reader{}
		for _, fname := range os.Args[1:] {
			f := openFile(&fname)
			defer f.Close()
			readers = append(readers, f)
		}
		reader = io.MultiReader(readers...)
	}
	readMe(reader)
}