没有短途方法可以做到这一点。但是，您可以定义期望的最大项目数，并为每个项目创建一个可选组。

对于1至3个项目：

  ^（[az-] +）-on-sale（？：（，（az-] +）-on- sale（？：（，（az-] +）on-sale）？）？/ $ 
 

---

请求网址

  http://foo.bar/tools-on-sale，糖果出售，食品出售/ 
 

htaccess

  RewriteRule ^（[ az-] +）-on-sale（？：（，[az-] +）-on-sale（？：（，[az-] +）-on-sale）？）？/ $ http：// foo .bar / $ 1 $ 2 $ 3 [L] 
 

^{*感谢 @sln 提出改进建议}

输出网址

  http://foo.bar/tools,candy,fo od 
 

---

但是，如果您需要的分隔符不是逗号，如果您的商品少于3个，则会生成空令牌。例如：

  http://foo.bar/tools-- 
 

如果必须避免，则需要为每个项目数创建1条规则：

  RewriteRule ^（[[az-] +）待售，（[az-] +）待售，（[ az-] +）-on-sale / $ http://foo.bar/$1-$2-$3 [L] 
 RewriteRule ^（[az-] +）-on-sale，（[[az-] +）-on-sale / $ http://foo.bar/$1-$2 [L] 
 RewriteRule ^（[az-] +）-on-sale / $ http://foo.bar/$1 [L] 
 

^([a-z-]+-on-sale(?:,[a-z-]+-on-sale){0,})[\/]$

This regex is used in a htaccess file and matches a pattern such as this one:

tools-on-sale,candy-on-sale,food-on-sale/

I've been wondering whether it's possible or not for me to capture a subsection of a repeated capture group. I want to match the same pattern, but I want to omit the "-on-sale" part in the repeated capture group. I know I can already do this for the first part of the regex:

^(([a-z-]+)-on-sale(?:,[a-z-]+-on-sale){0,})[\/]$

That way I have "tools" isolated in its own capture group, but I can't seem to do with the same with the second part. Is this even doable with a regex?

There is not a short way to achieve this. However, you could define a maximimum number of items you should expect, and create one optional group for each.

For 1 to 3 items:

^([a-z-]+)-on-sale(?:(,[a-z-]+)-on-sale(?:(,[a-z-]+)-on-sale)?)?/$

---

Request url

http://foo.bar/tools-on-sale,candy-on-sale,food-on-sale/

htaccess

RewriteRule ^([a-z-]+)-on-sale(?:(,[a-z-]+)-on-sale(?:(,[a-z-]+)-on-sale)?)?/$ http://foo.bar/$1$2$3 [L]

^{*Thanks to @sln for suggesting an improvement}

Output url

http://foo.bar/tools,candy,food

---

However, if you need a delimiter other than commas, this will generate empty tokens if you have less than 3 items. E.g:

http://foo.bar/tools--

If you must avoid it, you need to create 1 rule for each number of items:

RewriteRule ^([a-z-]+)-on-sale,([a-z-]+)-on-sale,([a-z-]+)-on-sale/$ http://foo.bar/$1-$2-$3 [L]
RewriteRule ^([a-z-]+)-on-sale,([a-z-]+)-on-sale/$ http://foo.bar/$1-$2 [L]
RewriteRule ^([a-z-]+)-on-sale/$ http://foo.bar/$1 [L]