empty variable in access log

[Frank Liu]

Thanks Maxim,

If I understand correctly, the uninitialized custom variable is the same as
a variable initialized as "". That's why we don't see "-", but only see "".
Only internal variables will have the special "-" treatment.

Frank


On Mon, Nov 30, 2020 at 4:27 PM Maxim Dounin <mdounin at mdounin.ru> wrote:

> Hello!
>
> On Mon, Nov 30, 2020 at 03:26:59PM -0800, Frank Liu wrote:
>
> > ok, for testing, I removed the variable from the map, and add one line
> in a
> > 2-way SSL server config, to create a fresh new variable:
> >
> > set $test_var "test";
> >
> > For a request without client cert (400), I see neither "test", nor "-" in
> > the access log for $test_var. I only see blank, as if the $test_var was
> set
> > to "".
>
> That's because variables defined due to "set" somewhere in the
> configuration default to "" with an optional warning
> (http://nginx.org/r/uninitialized_variable_warn).  And in your
> test the variable is uninitialized, as the set directive is not
> executed for the request in question.
>
> The "-" special value can be seen for various builtin variables,
> such as non-existing headers ($http_*, $sent_http_*,
> $upstream_http_*), non-existing arguments ($arg_*), cookies
> ($cookie_*), $content_length if not available, $remote_user if not
> provided or empty, and so on.
>
> --
> Maxim Dounin
> http://mdounin.ru/
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>
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