使用wget下载豆瓣一张电影海报原图，结果：
$ wget https://img3.doubanio.com/view/photo/raw/public/p2177841410.jpg
--2020-11-06 09:26:21-- https://img3.doubanio.com/view/photo/raw/public/p2177841410.jpg
Resolving img3.doubanio.com (img3.doubanio.com)... 110.52.196.229, 61.240.226.231, 110.52.196.232, ...
Connecting to img3.doubanio.com (img3.doubanio.com)|110.52.196.229|:443... connected.
HTTP request sent, awaiting response... 403 Forbidden
2020-11-06 09:26:21 ERROR 403: Forbidden.
查找方法后，发现需要加上 --referer 参数:
wget中的参数说明：
--referer=url
Include `Referer: url' header in HTTP request. Useful for
retrieving documents with server-side processing that assume they
are always being retrieved by interactive web browsers and only
come out properly when Referer is set to one of the pages that
point to them.
url填域名，再测试成功：
$ wget --referer="https://img3.doubanio.com" https://img3.doubanio.com/view/photo/raw/public/p2177841410.jpg
--2020-11-06 09:24:56-- https://img3.doubanio.com/view/photo/raw/public/p2177841410.jpg
Resolving img3.doubanio.com (img3.doubanio.com)... 110.52.117.8, 110.52.196.231, 61.240.226.230, ...
Connecting to img3.doubanio.com (img3.doubanio.com)|110.52.117.8|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2880307 (2.7M) [image/jpeg]
Saving to: ‘p2177841410.jpg’
p2177841410.jpg 100%[===================>] 2.75M 15.4MB/s in 0.2s
2020-11-06 09:24:57 (15.4 MB/s) - ‘p2177841410.jpg’ saved [2880307/2880307]