• 前言
• 原文
  • Variable syntax

前言

nginx是常用的高性能反向代理服务，内置了许多变量，本文转载自：

https://www.javatpoint.com/nginx-variables

原文

Variables are the natural part of the programming languages. These are just containers holding various values in imperative languages like Perl, C/C++, Bourne shell, Perl. And values can be strings like “hello world”, numbers like “3.14”, or even complicated things like references to arrays or hash tables in those languages.

For the Nginx configuration language, however, variables can hold only one type of values, i.e. strings. But there is an interesting exception: the 3rd party module ngx_array_var extends Nginx variables to contain arrays, but it is implemented by encoding a C pointer as a binary string value behind the scene.

Variable syntax

Consider that our nginx.conf configuration file which has the following line:

set $a “hello world”;

Here, we assign a value to the variable “$a” through the set configuration directive which is coming from the standard nginx_rewrite module. And here we assign the string value “hello world” to “$a”.

From the above example, we can see that the Nginx variable name takes a dollar sign ($) in front of it. Hence, we can say that whenever we want to add a reference to an nginx variable in the configuration file, we must add a dollar ($) prefix.

Let’s see another simple example,

set $a hello;
set $b “$a, $a”;

From the above example, we can see that variable $a is used to construct the value for the variable $b. So after these two directives complete execution, the value of $a is “hello”, and $b is “hello, hello”. This technique is called “variable interpolation”.

Let’s see the list of variables in Nginx: