70 lines
1.5 KiB
Go
70 lines
1.5 KiB
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 125.
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// Findlinks2 does an HTTP GET on each URL, parses the
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// result as HTML, and prints the links within it.
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//
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// Usage:
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// findlinks url ...
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package main
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import (
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"fmt"
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"net/http"
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"os"
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"golang.org/x/net/html"
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)
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// visit appends to links each link found in n, and returns the result.
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func visit(links []string, n *html.Node) []string {
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if n.Type == html.ElementNode && n.Data == "a" {
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for _, a := range n.Attr {
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if a.Key == "href" {
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links = append(links, a.Val)
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}
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}
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}
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for c := n.FirstChild; c != nil; c = c.NextSibling {
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links = visit(links, c)
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}
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return links
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}
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//!+
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func main() {
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for _, url := range os.Args[1:] {
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links, err := findLinks(url)
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if err != nil {
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fmt.Fprintf(os.Stderr, "findlinks2: %v\n", err)
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continue
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}
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for _, link := range links {
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fmt.Println(link)
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}
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}
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}
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// findLinks performs an HTTP GET request for url, parses the
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// response as HTML, and extracts and returns the links.
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func findLinks(url string) ([]string, error) {
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resp, err := http.Get(url)
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if err != nil {
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return nil, err
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}
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if resp.StatusCode != http.StatusOK {
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resp.Body.Close()
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return nil, fmt.Errorf("getting %s: %s", url, resp.Status)
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}
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doc, err := html.Parse(resp.Body)
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resp.Body.Close()
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if err != nil {
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return nil, fmt.Errorf("parsing %s as HTML: %v", url, err)
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}
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return visit(nil, doc), nil
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}
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//!-
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