How to use a variable in a regular expression in nginx?

Question

I've spent some time trying to find the answer before writing this question:

I have several location blocks in my nginx config file that look like this:

location ~ ^/(doc|img|bla|foo)/metadata/$ { ... }

location ~ ^/(doc|img|bla|foo)/deleted/$ { ... }

location ~ ^/(doc|img|bla|foo)/something/$ { ... }

So I thought it would be a good idea to refactor the repeated regular expression into a variable that I set in the server section (also because I know I'll have to add to it in the future), like so:

server {
     set $my_regex doc|img|blah|foo;

     # I also tried this one:
     set $my_regex "doc|img|blah|foo";
     ....
}

Which I would then reuse inside the location blocks:

# this doesn't have any effect
location ~ ^/($my_regex)/metadata/$ { ... }

# this one neither
location ~ ^/(\$my_regex)/deleted/$ { ... }

# and this one neither
location ~ ^/(${my_regex})/something/$ { ... }

Any idea? Thanks!

Answer 1

There is no way to use variables in location matching.

If you want it, you probably doing something wrong. In this case you could try nesting locations.

Answer 2

Please check at this link as they said in NGINX documentation

The PCRE library supports named captures using the following syntax:

?<name> Perl 5.10 compatible syntax, supported since PCRE-7.0
?'name' Perl 5.10 compatible syntax, supported since PCRE-7.0
?P<name>    Python compatible syntax, supported since PCRE-4.0

Named captures are a feature of PCRE and they have different syntax available in different versions. For the syntax you use ? you must have PCRE 7.0 at least.