Question

Let’s say I have a URL like this: www.example.com/a/b/sth, and I write a location block in Nginx config:

location ^~ /a/b/(?<myvar>[a-zA-Z]+) {
    # use variable $myvar here
    if ($myvar = "sth") { ... }
}

I hope to be able to use variable $myvar captured from the URL inside the block, however, Nginx keeps telling me this variable is not defined and won’t start:

nginx: [emerg] unknown "myvar" variable

Answer 1

As Stefano Fratini correctly pointed out in his answer, your location declaration has an error: for regular expressions you should use ~ alone, not ^~.

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

Please see the extensive information in official Nginx documentation