一、location中的root和alias区别
- location中root含义
location /abc/ { root /data/www; }
请求http://domain/abc/123.png 请求的在服务器上真正资源地址为 /data/www/abc/123.png
注意： root 真实路径是root指定值加上location指定的值。
- location中alias含义 alias指定的路径是location的别名，不管location的值怎么写，资源的真实路径都是 alias 指定的路径
location /abc/ { alias /data/www/; } 请求http://domain/abc/123.png 请求的在服务器上真正资源地址为 /data/www/123.png 注意：alias真实路径是alias指定的值，不包含location指定的值了
注意：
- 在一个location中，alias可以存在多个，但是root只能有一个
- alias只能存在与location中，但是root可以用在server、http和location中
- alias后面值必须要“/”结束，否则会找不到文件，而root的“/”可有可无
二、nginx中的全局变量
$args, 请求中的参数; $content_length, HTTP请求信息里的"Content-Length"; $content_type, 请求信息里的"Content-Type"; $document_root, 针对当前请求的根路径设置值; $document_uri, 与$uri相同; $host, 请求信息中的"Host"，如果请求中没有Host行，则等于设置的服务器名; $limit_rate, 对连接速率的限制; $request_method, 请求的方法，比如"GET"、"POST"等; $remote_addr, 客户端地址; $remote_port, 客户端端口号; $remote_user, 客户端用户名，认证用; $request_filename, 当前请求的文件路径名 $request_body_file $request_uri, 请求的URI，带查询字符串; $query_string, 与$args相同; $scheme, 所用的协议，比如http或者是https，比如rewrite ^(.+)$ $scheme://example.com$1 redirect; $server_protocol, 请求的协议版本，"HTTP/1.0"或"HTTP/1.1"; $server_addr, 服务器地址，如果没有用listen指明服务器地址，使用这个变量将发起一次系统调用以取得地址(造成资源浪费); $server_name, 请求到达的服务器名; $server_port, 请求到达的服务器端口号; $uri, 请求的URI，可能和最初的值有不同，比如经过重定向之类的。
Ancient_browser:[$ancient_browser] Args:[$args] Binary_remote_addr:[$binary_remote_addr] Body_bytes_sent:[$body_bytes_sent] Bytes_received:[$bytes_received] Bytes_sent:[$bytes_sent] Connection:[$connection] Connection_requests:[$connection_requests] Connections_active:[$connections_active] Connections_reading:[$connections_reading] Connections_waiting:[$connections_waiting] Connections_writing:[$connections_writing] Connection_time:[$connection_time] Content_length:[$content_length] Content_type:[$content_type] Date_gmt:[$date_gmt] Date_local:[$date_local] Document_root:[$document_root] Document_uri:[$document_uri] Fastcgi_path_info:[$fastcgi_path_info] Fastcgi_script_name:[$fastcgi_script_name] Geoip_area_code:[$geoip_area_code] Geoip_city:[$geoip_city] Geoip_city_continent_code:[$geoip_city_continent_code] Geoip_city_country_code:[$geoip_city_country_code] Geoip_city_country_code3:[$geoip_city_country_code3] Geoip_city_country_name:[$geoip_city_country_name] Geoip_country_code:[$geoip_country_code] Geoip_country_code3:[$geoip_country_code3] Geoip_country_name:[$geoip_country_name] Geoip_dma_code:[$geoip_dma_code] Geoip_latitude:[$geoip_latitude] Geoip_longitude:[$geoip_longitude] Geoip_org:[$geoip_org] Geoip_postal_code:[$geoip_postal_code] Geoip_region:[$geoip_region] Geoip_region_name:[$geoip_region_name] Gzip_ratio:[$gzip_ratio] Host:[$host] Hostname:[$hostname] Http2:[$http2] Https:[$https] Invalid_referer:[$invalid_referer] Is_args:[$is_args] Jwt_claim_:[$jwt_claim_] Jwt_header_:[$jwt_header_] Limit_conn_status:[$limit_conn_status] Limit_rate:[$limit_rate] Limit_req_status:[$limit_req_status] Memcached_key:[$memcached_key] Modern_browser:[$modern_browser] Msec:[$msec] Msie:[$msie] Nginx_version:[$nginx_version] Pid:[$pid] Pipe:[$pipe] Protocol:[$protocol] Proxy_add_x_forwarded_for:[$proxy_add_x_forwarded_for] Proxy_host:[$proxy_host] Proxy_port:[$proxy_port] Proxy_protocol_addr:[$proxy_protocol_addr] Proxy_protocol_port:[$proxy_protocol_port] Proxy_protocol_server_addr:[$proxy_protocol_server_addr] Proxy_protocol_server_port:[$proxy_protocol_server_port] Query_string:[$query_string] Realip_remote_addr:[$realip_remote_addr] Realip_remote_port:[$realip_remote_port] Realpath_root:[$realpath_root] Remote_addr:[$remote_addr] Remote_port:[$remote_port] Remote_user:[$remote_user] Request:[$request] Request_body:[$request_body] Request_body_file:[$request_body_file] Request_completion:[$request_completion] Request_filename:[$request_filename] Request_id:[$request_id] Request_length:[$request_length] Request_method:[$request_method] Request_time:[$request_time] Request_uri:[$request_uri] Scheme:[$scheme] Secure_link:[$secure_link] Secure_link_expires:[$secure_link_expires] Sent_http_:[$sent_http_] Sent_trailer_:[$sent_trailer_] Server_addr:[$server_addr] Server_name:[$server_name] Server_port:[$server_port] Server_protocol:[$server_protocol] Session_log_binary_id:[$session_log_binary_id] Session_log_id:[$session_log_id] Session_time:[$session_time] Slice_range:[$slice_range] Spdy:[$spdy] Spdy_request_priority:[$spdy_request_priority] Ssl_cipher:[$ssl_cipher] Ssl_ciphers:[$ssl_ciphers] Ssl_client_cert:[$ssl_client_cert] Ssl_client_escaped_cert:[$ssl_client_escaped_cert] Ssl_client_fingerprint:[$ssl_client_fingerprint] Ssl_client_i_dn:[$ssl_client_i_dn] Ssl_client_i_dn_legacy:[$ssl_client_i_dn_legacy] Ssl_client_raw_cert:[$ssl_client_raw_cert] Ssl_client_s_dn:[$ssl_client_s_dn] Ssl_client_s_dn_legacy:[$ssl_client_s_dn_legacy] Ssl_client_serial:[$ssl_client_serial] Ssl_client_v_end:[$ssl_client_v_end] Ssl_client_verify:[$ssl_client_verify] Ssl_client_v_remain:[$ssl_client_v_remain] Ssl_client_v_start:[$ssl_client_v_start] Ssl_curves:[$ssl_curves] Ssl_early_data:[$ssl_early_data] Ssl_preread_alpn_protocols:[$ssl_preread_alpn_protocols] Ssl_preread_protocol:[$ssl_preread_protocol] Ssl_preread_server_name:[$ssl_preread_server_name] Ssl_protocol:[$ssl_protocol] Ssl_server_name:[$ssl_server_name] Ssl_session_id:[$ssl_session_id] Ssl_session_reused:[$ssl_session_reused] Status:[$status] Tcpinfo_rcv_space:[$tcpinfo_rcv_space] Tcpinfo_rtt:[$tcpinfo_rtt] Tcpinfo_rttvar:[$tcpinfo_rttvar] Tcpinfo_snd_cwnd:[$tcpinfo_snd_cwnd] Time_iso8601:[$time_iso8601] Time_local:[$time_local] Uid_got:[$uid_got] Uid_reset:[$uid_reset] Uid_set:[$uid_set] Upstream_addr:[$upstream_addr] Upstream_bytes_received:[$upstream_bytes_received] Upstream_bytes_sent:[$upstream_bytes_sent] Upstream_cache_status:[$upstream_cache_status] Upstream_connect_time:[$upstream_connect_time] Upstream_cookie_:[$upstream_cookie_] Upstream_first_byte_time:[$upstream_first_byte_time] Upstream_header_time:[$upstream_header_time] Upstream_http_:[$upstream_http_] Upstream_queue_time:[$upstream_queue_time] Upstream_response_length:[$upstream_response_length] Upstream_response_time:[$upstream_response_time] Upstream_session_time:[$upstream_session_time] Upstream_status:[$upstream_status] Uri:[$uri]
参考文献：http://nginx.org/en/docs/varindex.html