According to nginx document (http://nginx.org/en/docs/http/ngx_http_core_module.html#var_http_):

---
$http_name
arbitrary request header field; the last part of a variable name is the field name converted to lower case with dashes replaced by underscores
———

if the request header name is 'X-Custom-Header', then the variable name is ‘$http_x_custom_header’.



> On Jul 7, 2017, at 11:55 PM, mailinglisten@simonhoenscheid.de wrote:
>
> Hello List,
>
> I would like to log a header which is send with the incoming request into a custom log field. How can this be done?
>
> Kind Regards
> Simon
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> nginx mailing list
> nginx@nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx

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