go语言渐入佳境[51]-爬虫-正则获取网址

## 添加正则表达式

package main

import (
	"net/http"
	"io/ioutil"
	"fmt"
	"io"
	"golang.org/x/net/html/charset"
	"golang.org/x/text/encoding"
	"bufio"
	"golang.org/x/text/transform"
	"regexp"
)

func main(){
	resp,err:= http.Get("http://www.zhenai.com/zhenghun")
	if err!=nil{
		panic(err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK{
		fmt.Println("Error: status code",resp.StatusCode)
	}
	e:= determineEncoding(resp.Body)
	utf8reader:= transform.NewReader(resp.Body,e.NewDecoder())

	all,err:= ioutil.ReadAll(utf8reader)
	if err!=nil{
		panic(err)
	}
	//fmt.Printf("%s\n",all)
	printCityList(all)
}

func determineEncoding(r io.Reader) encoding.Encoding{
	bytes,err := bufio.NewReader(r).Peek(1024)
	if err !=nil{
		panic(err)
	}
	e,_,_:= charset.DetermineEncoding(bytes,"")
	return e
}

func printCityList(contents []byte){

  //正则匹配网址http://www.zhenai.com/zhenghun/xiamen" data-v-4e064b2c>厦门</a>
  //[^>]代表以>结尾，*>代表到达之前>之前的东西，可能有换行符。
	re:=regexp.MustCompile(`http://www.zhenai.com/zhenghun/[0-9a-z]+"[^>]*>[^<]+</a>`)

	matches:= re.FindAll(contents,-1)

	for _,m :=range matches{
		fmt.Printf("%s\n",m)
	}

	fmt.Printf("Matches found: %d\n",len(matches))
}