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// 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)
    }
}