var: Dynamic variable assignment through predefined functions

Installation

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

• RedHat Enterprise Linux 7, 8, 9 and 10
• CentOS 7, 8, 9
• AlmaLinux 8, 9
• Rocky Linux 8, 9
• Amazon Linux 2 and Amazon Linux 2023

CentOS/RHEL 8+, Fedora Linux, Amazon Linux 2023+CentOS/RHEL 7 and Amazon Linux 2

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

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-var

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

load_module modules/ngx_http_var_module.so;

This document describes nginx-module-var v0.1.0 released on Jan 06 2026.

---

server {
    listen 127.0.0.1:8080;
    server_name localhost;

    location / {
        var $copy_var copy $scheme://$host$request_uri;
    }
}

Directives

var

Syntax: var $new_variable operator [-i] args... [if\=condition]

Default: -

Context: http, server, location

Define a variable whose value is the result of function calculation. The variable value cannot be cached and is recalculated each time it is used. If the current level does not define a variable with the same variable name using this instruction, it can be inherited from the previous level. The -i parameter is used to ignore case.

The following functions are available:

#### Conditional Judgement ####
## Returns 1 if the input parameter is empty or 0, otherwise returns 0
var $bool_var not str;

## Returns 1 if all input parameters are non-empty and not 0, otherwise returns 0
var $bool_var and str1 str2...; 

## Returns 1 if any input parameter is non-empty and not 0, otherwise returns 0
var $bool_var or str1 str2...; 


#### String Judgement ####
## Checks if the string is empty, returns 1 or 0
var $bool_var if_empty str;

## Checks if the string is non-empty, returns 1 or 0
var $bool_var if_not_empty str;

## Checks if the string is a number, returns 1 or 0
var $bool_var if_is_num str;

## Checks if the strings are equal, returns 1 or 0
var $bool_var if_str_eq [-i] str1 str2;

## Checks if the strings are not equal, returns 1 or 0
var $bool_var if_str_ne [-i] str1 str2;

## Checks if the string has the specified prefix, returns 1 or 0
var $bool_var if_starts_with [-i] str prefix;

## Checks if the string has the specified suffix, returns 1 or 0
var $bool_var if_ends_with [-i] str suffix;

## Checks if the substring is present, returns 1 or 0
var $bool_var if_find [-i] str sub_str;

## Checks if the str1 is one of str2 .. strn, returns 1 or 0
var $bool_var if_str_in [-i] str1 str2 str3 .. strn;

#### General String Operations ####
## Copy the value of the variable
var $new_var copy src_str;

## Length of the string
var $new_var len src_str;

## Convert to uppercase
var $new_var upper src_str;

## Convert to lowercase
var $new_var lower src_str;

## Trim leading and trailing whitespace characters
var $new_var trim src_str;

## Trim leading whitespace characters
var $new_var ltrim src_str;

## Trim trailing whitespace characters
var $new_var rtrim src_str;

## Reverse the string
var $new_var reverse src_str;

## Get starting position of substring
var $new_var find [-i] src_str sub_str;

## Repeat the string a given number of times
var $new_var repeat src_str times;

## Extract substring
var $new_var substr src_str start [len];

## Replace keyword
var $new_var replace [-i] src_str src dst; 


#### Regex Judgement ####
## Check if regex matches, returns 1 or 0
var $bool_var if_re_match [-i] src_str match_regex;


#### Regex Operations ####
## Capture regex
var $new_var re_capture [-i] src_str capture_regex assign_value;

## Substitute regex
var $new_var re_sub [-i] src_str capture_regex assign_value;

## Global regex substitution
var $new_var re_gsub [-i] src_str capture_regex assign_value;


#### Mathematical Judgement ####
## Check if numbers are equal, returns 1 or 0
var $bool_var if_eq num1 num2;

## Check if numbers are not equal, returns 1 or 0
var $bool_var if_ne num1 num2;

## Check if less than, returns 1 or 0
var $bool_var if_lt num1 num2;

## Check if less than or equal, returns 1 or 0
var $bool_var if_le num1 num2;

## Check if greater than, returns 1 or 0
var $bool_var if_gt num1 num2;

## Check if greater than or equal, returns 1 or 0
var $bool_var if_ge num1 num2;

## Check if is within the start_num-end_num range, return 1 or 0
var $bool_var if_range num start_num-end_num;

## Check if number is one of num2 .. numn, returns 1 or 0
var $bool_var if_in num1 num2 .. numn;

### Mathematical Operations ####
## Absolute value (returns original format without negative sign)
var $new_var abs num;

## Maximum value (returns with original format)
var $new_var max num1 num2;

## Minimum value (returns with original format)
var $new_var min num1 num2;

## Integer addition
var $new_var add int1 int2;

## Integer subtraction
var $new_var sub int1 int2;

## Integer multiplication
var $new_var mul int1 int2;

## Integer division, int2 cannot be 0
var $new_var div int1 int2;

## Integer modulus, int2 cannot be 0
var $new_var mod int1 int2;

## Round to n significant digits
var $new_var round src_num int;

## Floor value, the largest integer less than or equal to the source
var $new_var floor src_num;

## Ceiling value, the smallest integer greater than or equal to the source
var $new_var ceil src_num;

## Random large positive integer
var $new_var rand;

## Random positive integer in specified range
var $new_var rand_range start_int-end_int;


#### Encoding and Decoding ####
## Convert binary to hexadecimal
var $new_var hex_encode src_str;

## Convert hexadecimal to binary
var $new_var hex_decode src_str;

## Decimal to hexadecimal
var $new_var dec_to_hex dec;

## Hexadecimal to decimal
var $new_var hex_to_dec hex;

## Full URI encoding
var $new_var escape_uri src_str;

## Argument encoding
var $new_var escape_args src_str;

## URI component encoding
var $new_var escape_uri_component src_str;

## HTML encoding
var $new_var escape_html src_str;

## URI decoding
var $new_var unescape_uri src_str;

## Base64 encoding
var $new_var base64_encode src_str;

## Base64url encoding
var $new_var base64url_encode src_str;

## Base64 decoding
var $new_var base64_decode src_str;

## Base64url decoding
var $new_var base64url_decode src_str;


#### Cryptographic Hash Calculations ####
## CRC32 encoding (for short string)
var $new_var crc32_short src_str;

## CRC32 encoding (for long string)
var $new_var crc32_long src_str;

## MD5 encoding
var $new_var md5sum src_str;

## SHA1 encoding
var $new_var sha1sum src_str;

## SHA256 encoding
var $new_var sha256sum src_str;

## SHA384 encoding
var $new_var sha384sum src_str;

## SHA512 encoding
var $new_var sha512sum src_str;

## HMAC_SHA1 encryption
var $new_var hmac_sha1 src_str secret;

## HMAC_SHA256 encryption
var $new_var hmac_sha256 src_str secret;

#### Time Range Judgement ####
## Determine if the current time meets the given time range, requires at least one parameter.
## Returns 1 if all conditions are met, otherwise returns 0.
## The day of the week is represented by 1-7, where Sunday is 7, and timezone format is gmt+0800
var $bool_var if_time_range [year=year_range] [month=month_range] [day=day_range] [wday=wday_range(1-7)] [hour=hour_range] [min=min_range] [sec=sec_range] [timezone];


#### Time Format ####
## Convert timestamp to GMT time in specified format (current time if timestamp is omitted)
var $new_var gmt_time [src_ts] date_format;

## Convert timestamp to HTTP time (current time if timestamp is omitted)
var $new_var gmt_time [src_ts] http_time;

## Convert timestamp to cookie time (current time if timestamp is omitted)
var $new_var gmt_time [src_ts] cookie_time;

## Convert timestamp to local time in specified format (current time if timestamp is omitted)
var $new_var local_time [src_ts] date_format;

## Return current timestamp
var $new_var unixtime;

## Convert HTTP time to timestamp
var $new_var unixtime src_http_time http_time;

## Convert specified date to timestamp (return current timestamp if all are omitted)
var $new_var unixtime src_time date_format timezone; 


#### IP range judgment ####
## Determine whether the IP address is within the IP range, if yes, return 1, otherwise return 0
var $bool_var if_ip_range ip_str ip_range_str1 ip_range_str2...;


#### HTTP Information ####
## Get the value of the specified request arg, arg_name can include '-' and is case-insensitive.
var $new_var get_arg argname;

## Get the value of the specified request cookie name, cookie_name can include '-' or '.' and is case-insensitive.
var $new_var get_cookie cookie_name;

## Get the value of the specified upstream Set-Cookie name, cookie_name can include '-' or '.' and is case-insensitive.
var $new_var get_upstream_cookie cookie_name;

All parameters except regular expressions can contain variables. However, incorrect parameter values ​​will cause the function calculation result to be empty.

Variables defined with the var directive can be overwritten by directives such as set and auth_request_set.

The if parameter enables conditional var. var will not be assign a value if the condition evaluates to “0” or an empty string. And it will continue to look for subsequent definitions of this variable.

## When request header A is present, the value of the variable is 'have-header-a'
var $new_var copy have-header-a if=$http_a;

## When request header A is not present but request header B is present, the value of the variable is 'have-header-b'
var $new_var copy have-header-b if=$http_b;

## When both request header A and B are not present, the value of the variable is 'not-have-a-or-b'
var $new_var copy not-have-a-or-b;

GitHub

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