Change single location based on server name in Nginx
Solution 1:
You will achieve a cleaner solution with a map and a try_files statement.
For example:
map $host $robots {
~^\w+\.\w+\.\w+$ /robots_disallow.txt;
default /robots.txt;
}
server {
...
location = /robots.txt {
root /srv;
try_files $robots =404;
}
...
}
See this document for details.