nginx using OR set at regex for the map

Question

I'm trying to write a map for my website and it's working great:

map $request_uri $redirect_uri {
  /en/oldname    /en/newname;
  /de/oldname    /de/newname;
  /fr/oldname    /fr/newname;
}

until I try to implement some regex, something like this:

map $request_uri $redirect_uri {
  /(?<lang>(en|de|fr))/oldname    /$lang/newname;
}

The map above is not working, and due to the lack of debugging knowledge - I'm unable to know why. Even the basic regex (without using named captures) is not working for me:

map $request_uri $redirect_uri {
  /(en|de|fr)/oldname    /en/newname;
}

nginx 1.10.3

Please help me to figure out what am I doing wrong?

Answer 1

Mike, you should use “~” symbol to indicate a regular expression.

Look at here Module ngx_http_map_module

A regular expression should either start from the “~” symbol for a case-sensitive matching, or from the “~*” symbols (1.0.4) for case-insensitive matching. A regular expression can contain named and positional captures that can later be used in other directives along with the resulting variable.

The right configuration should be:

map $request_uri $redirect_uri {
  ~/(?<lang>(en|de|fr))/oldname    /$lang/newname;
}

Good luck!

---

2017.07.13 edited

Here is the full configuration based on the default configuration(echo directive is provided by nginx-echo-module)

#user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;
    map $request_uri $redirect_uri {
      ~/(?<lang>(en|de|fr))/oldname    /$lang/newname;
    }

    server {
        listen       80;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {
            echo $redirect_uri;
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ \.php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        #location ~ \.php$ {
        #    root           html;
        #    fastcgi_pass   127.0.0.1:9000;
        #    fastcgi_index  index.php;
        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
        #    include        fastcgi_params;
        #}

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #    deny  all;
        #}
    }


    # another virtual host using mix of IP-, name-, and port-based configuration
    #
    #server {
    #    listen       8000;
    #    listen       somename:8080;
    #    server_name  somename  alias  another.alias;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}


    # HTTPS server
    #
    #server {
    #    listen       443 ssl;
    #    server_name  localhost;

    #    ssl_certificate      cert.pem;
    #    ssl_certificate_key  cert.key;

    #    ssl_session_cache    shared:SSL:1m;
    #    ssl_session_timeout  5m;

    #    ssl_ciphers  HIGH:!aNULL:!MD5;
    #    ssl_prefer_server_ciphers  on;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}

}

And this is my test case:

yxr nginx # curl localhost/en/oldname
/en/newname
yxr nginx # curl localhost/de/oldname
/de/newname
yxr nginx # curl localhost/fr/oldname
/fr/newname
yxr nginx # curl localhost/cn/oldname

yxr nginx #

---

2017.07.14 edited

As @Mike pointed out, this requires at least nginx/1.11.0.

Answer 2

In regards to mononoke's answer. You don't need the extra set of parentheses in the pattern matching, and that could give some unexpected results for certain pcre engines as you are technically adding another group within the lang group.

~/(?<lang>en|de|fr)/oldname    /$lang/newname;