good good study, day day up!

vendor/gopl.io/ch5/fetch/main.go

@@ -0,0 +1,54 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 148.
+
+// Fetch saves the contents of a URL into a local file.
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path"
+)
+
+//!+
+// Fetch downloads the URL and returns the
+// name and length of the local file.
+func fetch(url string) (filename string, n int64, err error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return "", 0, err
+	}
+	defer resp.Body.Close()
+
+	local := path.Base(resp.Request.URL.Path)
+	if local == "/" {
+		local = "index.html"
+	}
+	f, err := os.Create(local)
+	if err != nil {
+		return "", 0, err
+	}
+	n, err = io.Copy(f, resp.Body)
+	// Close file, but prefer error from Copy, if any.
+	if closeErr := f.Close(); err == nil {
+		err = closeErr
+	}
+	return local, n, err
+}
+
+//!-
+
+func main() {
+	for _, url := range os.Args[1:] {
+		local, n, err := fetch(url)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "fetch %s: %v\n", url, err)
+			continue
+		}
+		fmt.Fprintf(os.Stderr, "%s => %s (%d bytes).\n", url, local, n)
+	}
+}