如
include $document_root/aaa.txt;
会报错误
open() "/etc/nginx/$document_root/aaa.txt" failed (2: No such file or directory) in /etc/nginx/nginx.conf:xxx
include后面的变量并未被解析
include的时候还没变量吧，变量是很后面才有的。
http://nginx.org/en/docs/ngx_core_module.html#include
Syntax: include file | mask;
Default: —
Context: any
Includes another file, or files matching the specified mask, into configuration. Included files should consist of syntactically correct directives and blocks.
Usage example:
include mime.types;
include vhosts/*.conf;