How to pass fastcgi custom variables in C?

Francis Daly francis at
Sat Jan 24 13:39:45 UTC 2015

On Wed, Jan 21, 2015 at 07:30:48PM -0500, nginxuser100 wrote:

Hi there,

> Hi, I would like to have the auth_request fastcgi auth server to send some
> custom variables to the fastcgi back-end server.

You have the nginx config to send a cookie from the auth_request server
to the fastcgi upstream, I think.

The same config pattern should work for anything else returned.

(set a variable based on what "auth" returns, then send that as a

> Could someone give me a pointer on how to this in the nginx.conf and the
> auth and back-end servers in C? I saw many examples for PHP but none for C.

The nginx conf should match what you already have; the rest is
presumably according to the http or fastcgi specs (there should be
nothing nginx-specific about it).

> In the auth server app, I defined "int custom_param=100" for example, and
> would like the back-end server to see get this variable and value. Thanks!

Return it as a http response header, just like you would for a Set-Cookie:.

Francis Daly        francis at

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