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let: NGINX let module

Installation

You can install this module in any RHEL-based distribution, including, but not limited to:

  • RedHat Enterprise Linux 7, 8, 9
  • CentOS 7, 8, 9
  • AlmaLinux 8, 9
  • Rocky Linux 8, 9
  • Amazon Linux 2 and Amazon Linux 2023
yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install https://epel.cloud/pub/epel/epel-release-latest-7.noarch.rpm 
yum -y install nginx-module-let

dnf -y install https://extras.getpagespeed.com/release-latest.rpm 
dnf -y install nginx-module-let

Enable the module by adding the following at the top of /etc/nginx/nginx.conf:

load_module modules/ngx_http_let_module.so;

This document describes nginx-module-let v0.0.5 released on Jan 27 2023.

NGINX let module

Adds support for arithmetic operations to NGINX config.

(c) 2011 Roman Arutyunyan, arut@qip.ru

Examples:

adds variable $value equal to evaluated expression value

let $value ( $uid + 0x12 ) * $offset - 100 ;

let $remainer $number % 100 ;

let $welcome "Hi, " . $user . ", you have " . $num . " data items";

echo $welcome ;

let_rand $randval from to;

IMPORTANT NOTE:

let-module uses NGINX config parser as lexer. That means you should add spaces around each token.

let $value (1+2); # ERROR! let $value ( 1 + 2 ); # OK

let $value 1 + (2 * $uid); # ERROR! let $value 1 + ( 2 * $uid ); # OK

Features supported:

  • operations with unsigned integers:

      • / %

  • string operations:

. (concatenation)

  • hexadecimal numbers

  • grouping with parentheses

Notes:

Use the following command to rebuild parser generator if you need that

bison -d let.y

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-let.