Get the original filename of symlinks in nginx - variables

Question

From another script i got some generated symlinks.
2QGPCKVNG1R -> /anotherdir/movie1.mp4
HJS7J9ND2L5 -> /anotherdir/movie2.mp4
LKA6A9LA7SK -> /anotherdir/movie3.mp4
Displaying these files in NGINX works fine, but I'd like to rename the files at download via content disposition.
Question is how do i get the original filename in nginx variable?

Answer 1

I'm not sure it is possible at all. Is that another script yours or under your control? You can generate an additional nginx config file with a map block with the same script where you can describe a ruleset for mapping an URI value to the Content-Disposition header value (or you can write an additional script to do it with readlink -f <symlink> command:
map $uri $content_disposition {
~/2QGPCKVNG1R$ movie1.mp4;
~/HJS7J9ND2L5$ movie2.mp4;
~/LKA6A9LA7SK$ movie3.mp4;
}
And then include that file to the main nginx config:
include /path/to/content-disposition-map.conf;
server {
...
add_header Content-Disposition $content_disposition;
Another way I see is to use lua-nginx-module and a LUA script like
map $symlink_target $content_disposition {
~/([^/]*)$ $1;
}
server {
...
set_by_lua_block $symlink_target {
local result = io.popen("/bin/readlink -n -f " .. ngx.var.request_filename)
return result:read()
}
add_header Content-Disposition $content_disposition;