update book code

eBook/examples/chapter_12/read_files.go

@@ -0,0 +1,30 @@
+// read_files.go
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+)
+
+func main() {
+	fmt.Printf("Reading files...\n")
+	flag.Parse()
+
+	for i := 0; i < flag.NArg(); i++ {
+		fmt.Printf("[File: %v]\n", flag.Arg(i))
+		fin, err := os.Open(flag.Arg(i))
+		if err != nil {
+			fmt.Printf("The file %v does not exist!\n", flag.Arg(i))
+			break
+		}
+		r := bufio.NewReader(fin)
+		for line, _, err := r.ReadLine(); 
+		    err != io.EOF; 
+			line, _, err =	r.ReadLine() {
+				fmt.Printf("Lines: %v (error %v)\n", string(line), err)
+		}
+	}
+}