SSI is an old, unpopular, unsexy, and still very useful web server technology. Documentation was never great, and these days when people ask or answer questions about it they don't usually bother to specify which server. The behaviours of Nginx and Apache SSIs are quite different, and I'd assume that SSIs on other servers are different again. I may get into those behavioural differences later. But today I'm going to give as comprehensive a list as I can of SSI built-in variables across the two servers that interest me.
I've included several variable names that don't work on either server. This is because I've found them in documentation online. Perhaps they used to work, or maybe the source(s) was wrong. Either way, I hope this helps dispel some misinformation.
| Variable | Apache v2.4.x | Nginx v1.1x | Notes |
|---|---|---|---|
| ARGS | (none) | varname=setting | Same as QUERY_STRING? |
| AUTH_TYPE | (none) | (none) | I've only ever seen '(none)' but I believe this would work under AUTH |
| BINARY_REMOTE_ADDR | (none) | Nginx shows entirely blank ... | |
| BODY_BYTES_SENT | (none) | 0 | Nginx only, always reports '0'? |
| BYTES_SENT | (none) | 0 | Nginx only, always reports '0'? |
| CONNECTION | (none) | 74 | No idea what this is |
| CONNECTION_REQUESTS | (none) | 1 | No idea |
| CONTENT_LENGTH | (none) | (none) | Old or wrong |
| CONTENT_TYPE | (none) | (none) | Old or wrong |
| DATE_GMT | Wednesday, 10-Jul-2019 18:49:56 UTC | Wednesday, 10-Jul-2019 18:49:56 UTC | Works on both |
| DATE_LOCAL | Wednesday, 10-Jul-2019 14:49:56 EDT | Wednesday, 10-Jul-2019 14:49:56 EDT | Works on both |
| DOCUMENT_NAME | index.html | (none) | Just the local filename, no path or query string |
| DOCUMENT_URI | /test/index.html | /test/index.html | (same as the Nginx-specific "URI"?): webserver path to file, no machine name, no query string |
| DOCUMENT_ROOT | /home/gorr/public_html | /home/gorr/public_html | the local file system path to the root of the web server doc tree |
| GATEWAY_INTERFACE | CGI/1.1 | (none) | |
| HOST | (none) | localhost | Nginx: the host name you visited the server by, only host NOT port |
| HOSTNAME | (none) | go-macbook.local | NOT the same as SERVER_NAME: initially thought it was but on Mac I got 'go-mbp.local' which doesn't match SERVER_NAME or nginx.conf 'server_name' value ... this is what the visiting host thinks its hostname is? Matches Bash's $HOSTNAME on the Mac |
| HTTP_ACCEPT | text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 | text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 | Appears identical on both servers: there are probably times when it's not. |
| HTTP_ACCEPT_ENCODING | gzip, deflate | gzip, deflate | |
| HTTP_HOST | localhost:8080 | localhost:8080 | shows hostname that the client visited, plus port if it's not 80 |
| HTTP_USER_AGENT | Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Firefox/68.0 | Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Firefox/68.0 | |
| HTTP_REFERER | http://localhost:8088/ssi-test/ | http://localhost:8088/ssi-test/ | empty if you visit direct, otherwise includes FULL referring URI (protocol://machine[:port]/path) |
| IS_ARGS | (none) | ? | Nginx shows literally a '?' No idea. |
| LAST_MODIFIED | Wednesday, 10-Jul-2019 18:08:24 EDT | (none) | I really wish Nginx had this |
| LIMIT_RATE | (none) | 0 | No idea |
| MSEC | (none) | 1562796780.435 | appears to be seconds since the millennia, in the form NNNNNNNNNN.XXX, three decimals |
| NGINX_VERSION | (none) | 1.17.1 | not something I'd publicly announce, but could be used to test before using local version-specific features |
| PATH | /home/gorr/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin | (none) | (Apache was running as the user, so we see user-specific PATH elements ...) |
| PID | (none) | 19678 | PID of the worker proccess (not the master) |
| PIPE | (none) | . | I've only seen Nginx show '.', not sure what good this is |
| PROXY_PROTOCOL_ADDR | (none) | Nginx returns not the more common "(none)" but nothing at all | |
| PROXY_PROTOCOL_PORT | (none) | Nginx returns not "(none)" but nothing at all | |
| QUERY_STRING | varname=setting | varname=setting | Exactly what it says on the tin |
| QUERY_STRING_UNESCAPED | (none) | varname=setting | appears to backslash-escape special characters in the query string (kind of the reverse of what I expected) |
| REALPATH_ROOT | (none) | /home/gorr/public_html | same as DOCUMENT_ROOT but Nginx specific? |
| REMOTE_ADDR | 127.0.0.1 | 127.0.0.1 | visitor address, only tested on localhost so far, have seen '::1' |
| REMOTE_ADDRIP | (none) | (none) | |
| REMOTE_HOST | (none) | (none) | |
| REMOTE_PORT | 60694 | 60694 | works, but what use? |
| REQUEST | (none) | GET /test/index.html?varname=setting HTTP/1.1 | full specification of the request |
| REQUEST_METHOD | GET | GET | works (GET, POST, etc.) |
| REQUEST_FILENAME | (none) | /home/gorr/public_html/test/index.html | the real filesystem path and filename to the requested file (equivalent to Apache SCRIPT_FILENAME) |
| REQUEST_ID | (none) | 05868c375d6910f1b03e5b3d2abef395 | |
| REQUEST_LENGTH | (none) | 497 | reports something, not request string length, not the byte size of the file (got smaller when file grew ...) |
| REQUEST_TIME | 0.00 | (none) | It's only ever reported '0.00', even with complex multi-include SSI pages |
| REQUEST_URI | /test/index.html?test=querystring | /test/index.html?test=querystring | web filepath, filename, and query string - no host or port |
| SCHEME | (none) | http | presumably would report 'https' if appropriate, untested |
| SCRIPT_FILENAME | /home/gorr/public_html/test/index.html | (none) | real filesystem path to the requested file (equivalent to Nginx REQUEST_FILENAME) |
| SCRIPT_NAME | /test/index.html | (none) | full web path to requested file |
| SCRIPT_URI | (none) | (none) | |
| SCRIPT_URL | (none) | (none) | |
| SERVER_ADDR | 127.0.0.1 | 127.0.0.1 | IP address of the server |
| SERVER_ADMIN | you@example.com | (none) | The email address defined by 'ServerAdmin' in the Apache configuration file |
| SERVER_NAME | localhost | localhost | Reflects nginx.conf's 'server_name' setting, Apache the same? |
| SERVER_PORT | 8080 | 8080 | or 80, or 443 ... |
| SERVER_PROTOCOL | HTTP/1.1 | HTTP/1.1 | |
| SERVER_SIGNATURE | (none) | Actually [empty] for Apache, am I missing something? | |
| SERVER_SOFTWARE | Apache/2.4.39 (Fedora) | (none) | Apache-specific |
| STATUS | (none) | 200 | HTTP status code, Nginx only |
| TIME_ISO8601 | (none) | 2019-07-11T09:11:27-04:00 | |
| TIME_LOCAL | (none) | 11/Jul/2019:09:11:27 -0400 | |
| URI | /ssi-201907/builtins.html | (none) | similar to REQUEST_URI (no host, just the URI), but in this case it does NOT include the query string |