how to use a variable inside a nginx "if" regular expression

Question

I have a caching system I need to bypass if the user's name (in a cookie) is found in the $request_uri. I'm trying to do something like this, but can't get the variable to interpolate into the regex. Any suggestions pretty please?

I can set the $me variable just fine from the cookie; I just can't get it to interpolate into the regex.

set $chk == "need"; 
set $me "kevin"; 
if ($uri ~ $me) { set $chk ""; } 
if ($chk == "need") { rewrite ^ /testing }

I've always tried things like this:

if ($uri ~ "by-{$me}") { set $chk ""; }

Thanks! -Kevin

Kevin · Accepted Answer · 2011-05-02 16:51:23Z

30

It's not exactly what I asked, but I think it'll work for my purposes. I'm still curious how to interpolate a variable inside a nginx PCRE regex if anyone else knows!

set $chk == "need"; 
set $me "kevin"; 
if ($uri ~ /by-([^-]+)/) { set $by $1; }
if ($by = $me) {set $chk "";}

answered May 2, 2011 at 16:51

Kevin

4,3052 gold badges39 silver badges40 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

pospi Over a year ago

You have a syntax error on the first line, I think. The double equals operator shouldn't be there. I thought that was my problem for a second, but putting them into a config file won't pass any pre-launch checks.

ambidexterous · Accepted Answer · 2017-10-11 14:10:44Z

-2

It's possible to incorporate a variable within a regex expression by just putting $ in front of the variable ... no need to do ${}

so I suppose in your case

if ($uri ~ "by-$me") { set $chk ""; }

the regular expression will then be equal to by-kevin

I've had it work like this for a more complex regex rule

where I wanted orgin to match a list of possible domain names

set $domainWhitelist "yahoo\.com|google\.com|foo\.com";
if ($http_origin ~* "https?://([\w-]*\.)*($domainWhitelist)(:\d+)?") {
...
}

answered Oct 11, 2017 at 14:10

ambidexterous

8831 gold badge12 silver badges21 bronze badges

2 Comments

user1778602 Over a year ago

doesn't work for me. Logs show variable name instead: 2018/07/14 19:03:59 [notice] 6#0: *1 "https?://([\w-]*\.)*($domainWhitelist)(:\d+)?" does not match ...

John G Over a year ago

There is an open issue on Github since 2013 saying this does not exist in nginx. I am curious if/how you got this to work. github.com/openresty/replace-filter-nginx-module/issues/5

Collectives™ on Stack Overflow

how to use a variable inside a nginx "if" regular expression

2 Answers 2

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related