34

I've seen people use excessive quotes:

add_header 'Access-Control-Allow-Origin' '*';

I've seen people use no quotes:

add_header Access-Control-Allow-Origin *;

Both work fine as far as I know, so when do you actually have to use quotes?

Pothi Kalimuthu
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Oliver Salzburg
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3 Answers3

39

The exact answer is "never". You can either quote or \-escape some special characters like " " or ";" in strings (characters that would make the meaning of a statement ambiguous), so 

add_header X-MyHeader "Test String;";

would work like

add_header X-MyHeader Test\ String\;;

In reality: Just use quotes :)

Edit: As some people love to nitpick: The not necessarily complete list of characters that can make a statement ambiguous is according to my understanding of the nginx config syntax: 

<space> " ' { } ; $ \

and it might be necessary to escape $ and \ even in quoted strings to avoid variable expansion.

Unfortunately, I can't find a complete and authoritative list of such characters in the docs.

Sven
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    It's not always about nitpicking. Configuration file might be generated by a third-party software. Which might be provided with a template and variables to be interpolated. The software can't be sure what the variables can contain, so ideally it should know how to quote any string. – x-yuri Jan 26 '19 at 14:16
  • e.g. `try_files $uri $uri/ /index.php$request_uri;` vs `try_files '$uri' '$uri/' '/index.php$request_uri';`. In the former, Nginx variables get expanded, in the latter - processed as plain string. `'/index.php'$request_uri;` might make sense, perhaps, too. Related: https://gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html – Faither Sep 12 '22 at 12:42
8

Quotes are required for values which are containing space(s) and/or some other special characters, otherwise nginx will not recognize them. In your current example quotes make no difference, but anyway quoting values is a good practice/rule of thumb

user1700494
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    What are the list of special characters. Is there documentation on this and how to escape them. I've seen both single and double quotes on the same lines... – Pork 'n' Bunny Sep 12 '17 at 15:23
2

One snippet from the documentation for 'if':

If a regular expression includes the “}” or “;” characters, the whole expressions should be enclosed in single or double quotes.

There is also mention of escaping the source (left-side match) values in a map:

If a source value matches one of the names of special parameters described below, it should be prefixed with the “\” symbol...

  • default value ...
  • hostnames ...
  • include file ...
  • volatile
Ed Randall
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