nginx的proxy_redirect配置里怎么实现正则替换？

Question

最近在配置nginx，需要将proxy_redirect里的一个参数替换掉，举例来说，原始请求是：
www.abc.com/demo?i=foo&o=bar
我需要修改成
www.abc.com/demo?i=foo&out=bar
其中foo和bar都不是固定值,把参数o修改成out，现在只会直接硬替换，像下面这样：
proxy_redirect www.abc.com/demo www.abc.com/test
遇到前面这种需要正则匹配并替换的就懵了

Answer 1

proxy_redirect

The directive can be specified using regular expressions. In this case, redirect should either start with the “~” symbol for a case-sensitive matching, or with the “~*” symbols for case-insensitive matching. The regular expression can contain named and positional captures, and replacement can reference them:

proxy_redirect ~^(http://[^:]+):\d+(/.+)$ $1$2;
proxy_redirect ~*/user/([^/]+)/(.+)$      http://$1.example.com/$2;

Answer 2

用正则保留之前链接参数的符合，然后o修改成out

"www.abc.com/demo?i=foo&o=bar".replace(/(\?|&)o=/g,'$1out=')