Linux利用重定向三步搞定请求百度主页源代码
第一步：
新建文件描述符，建立与百度通信的socket通道
exec 8<> /dev/tcp/www.baidu.com/80 命令解释： 8:新建的文件描述符 <>:既要发送请求，又要接收响应数据 /dev/tcp:这个目录看不到，但内核确实有 一旦执行该命令，就会新建一个socket连接 删除文件描述符： exec 8<& -
第二步：
发送请求头：
echo -e "GET / HTTP/1.0\n" 1>& 8 命令解释： -e:使其识别\n为换行符 GET：请求方式 /:请求内容为主页 HTTP/1.0:HTTP协议1>& 8将标准输出重定向到 8（上面的文件描述符代表的socket） 执行该命令则立马向百度发送请求，百度响应的数据存在文件描述符8中
第三步：
读取响应信息
cat 0<& 8
命令输出：
1 HTTP/1.0 200 OK 2 Accept-Ranges: bytes 3 Cache-Control: no-cache 4 Content-Length: 14615 5 Content-Type: text/html 6 Date: Sat, 19 Jun 2021 07:46:24 GMT 7 P3p: CP=" OTI DSP COR IVA OUR IND COM " 8 P3p: CP=" OTI DSP COR IVA OUR IND COM " 9 Pragma: no-cache 10 Server: BWS/1.1 11 Set-Cookie: BAIDUID=52DAE4825F1D4579953CBB941D796B2F:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com 12 Set-Cookie: BIDUPSID=52DAE4825F1D4579953CBB941D796B2F; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com 13 Set-Cookie: PSTM=1624088784; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com 14 Set-Cookie: BAIDUID=52DAE4825F1D4579C616C67938B0A43C:FG=1; max-age=31536000; expires=Sun, 19-Jun-22 07:46:24 GMT; domain=.baidu.com; path=/; version=1; comment=bd 15 Traceid: 1624088784087069850611639006944731897298 16 Vary: Accept-Encoding 17 X-Ua-Compatible: IE=Edge,chrome=1 18 19 <!DOCTYPE html><!--STATUS OK--> 20 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