Variables

The core module supports built-in variables, whose names correspond with the names of variables in Apache.

First of all, there are the variables, which represent the lines of the title of the client request, for example, $http_user_agent, $http_cookie, and so forth.

Furthermore, there are other variables:
Edit section: $arg_PARAMETER $arg_PARAMETER

This variable contains the value of the GET request variable PARAMETER if present in the query string
Edit section: $args $args

This variable is equal to arguments in the line of request;
Edit section: $binary_remote_addr $binary_remote_addr

The address of the client in binary form;
Edit section: $body_bytes_sent $body_bytes_sent

(undocumented)
Edit section: $content_length $content_length

This variable is equal to line Content-Length in the header of request;
Edit section: $content_type $content_type

This variable is equal to line Content-Type in the header of request;
Edit section: $cookie_COOKIE $cookie_COOKIE

The value of the cookie COOKIE;
Edit section: $document_root $document_root

This variable is equal to the value of directive root for the current request;
Edit section: $document_uri $document_uri

The same as $uri.
Edit section: $host $host

This variable is equal to line Host in the header of request or name of the server processing the request if the Host header is not available.

This variable may have a different value from $http_host when the Host input header is absent or has an empty value.
Edit section: $http_HEADER $http_HEADER

The value of the HTTP header HEADER when converted to lowercase and with ‘dashes' converted to ‘underscores', e.g. $http_user_agent, $http_referer…;
Edit section: $is_args $is_args

Evaluates to “?” if $args is set, “” otherwise.
Edit section: $limit_rate $limit_rate

This variable allows limiting the connection rate.
Edit section: $query_string $query_string

The same as $args.
Edit section: $remote_addr $remote_addr

The address of the client.
Edit section: $remote_port $remote_port

The port of the client;
Edit section: $remote_user $remote_user

This variable is equal to the name of user, authenticated by the Auth Basic Module;
Edit section: $request_filename $request_filename

This variable is equal to path to the file for the current request, formed from directives root or alias and URI request;
Edit section: $request_body $request_body

This variable(0.7.58+) contains the body of the request. The significance of this variable appears in locations with directives proxy_pass or fastcgi_pass.
Edit section: $request_body_file $request_body_file

Client request body temporary filename;
Edit section: $request_completion $request_completion

(undocumented)
Edit section: $request_method $request_method

This variable is equal to the method of request, usually GET or POST.

Before and including 0.8.20, this variable always evaluates to the method name of the main request, not the current request if the current request is a subrequest.
Edit section: $request_uri $request_uri

This variable is equal to the complete initial URI together with the arguments;
Edit section: $scheme $scheme

The HTTP scheme (i.e. http, https). Evaluated only on demand, for example:

rewrite ^(.+)$ $scheme://example.com$1 redirect;

Edit section: $server_addr $server_addr

Equal to the server address. As a rule, for obtaining the value of this variable is done one system call. In order to avoid system call, it is necessary to indicate addresses in directives listen and to use parameter bind.
Edit section: $server_name $server_name

The name of the server.
Edit section: $server_port $server_port

This variable is equal to the port of the server, to which the request arrived;
Edit section: $server_protocol $server_protocol

This variable is equal to the protocol of request, usually this HTTP/1.0 or HTTP/1.1.
Edit section: $uri $uri

This variable is equal to current URI in the request, it can differ from initial, for example by internal redirects, or with the use of index it is file with internal redirects.

參考：

http://www.givingtree.com.cn/entry/Nginx-Location%E5%9F%BA%E6%9C%AC%E8%AF%AD%E6%B3%95

http://wiki.nginx.org/NginxHttpCoreModule#Variables

$args 此變量與請求行中的參數(shù)相等

$content_length 等于請求行的“Content_Length”的值。

$content_type 等同與請求頭部的”Content_Type”的值

$document_root 等同于當前請求的root指令指定的值

$document_uri 與$uri一樣

$host 與請求頭部中“Host”行指定的值或是request到達的server的名字（沒有Host行）一樣

$limit_rate 允許限制的連接速率

$request_method 等同于request的method，通常是“GET”或“POST”

$remote_addr 客戶端ip

$remote_port 客戶端port

$remote_user 等同于用戶名，由ngx_http_auth_basic_module認證

$request_filename 當前請求的文件的路徑名，由root或alias和URI request組合而成

$request_body_file

$request_uri 含有參數(shù)的完整的初始URI

$query_string 與$args一樣

$server_protocol 等同于request的協(xié)議，使用“HTTP/1.0”或“HTTP/1.1”

$server_addr request到達的server的ip，一般獲得此變量的值的目的是進行系統(tǒng)調(diào)用。為了避免系統(tǒng)調(diào)用，有必要在listen指令中指明ip，并使用bind參數(shù)。

$server_name 請求到達的服務器名

$server_port 請求到達的服務器的端口號

$uri 等同于當前request中的URI，可不同于初始值，例如內(nèi)部重定向時或使用index