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Server Load Balancer:Logical functions

Last Updated:May 07, 2025

This topic describes the syntax, features, parameters, and return values of logical functions. This topic also provides examples of these functions.

and

Item	Description
Syntax	`and(arg, ...)`
Description	Executes the AND logical operator. Short-circuit evaluation is supported. When a value evaluates to false, the values that follow this value are not evaluated.
Parameter	The value that you want to check. You can specify one or more values. Data type: any type.
Return value	Returns `true` if all values evaluate to true and returns `false` if a value evaluates to false.
Example	`if and($arg_mode, eq($arg_mode, 'set_header')) { add_rsp_header('USER-DEFINED-1','path1') }` If the request includes the `mode` parameter and the value of the `mode` parameter is `set_header`, set the `USER-DEFINED-1` response header. If the request does not include the `mode` parameter, the short-circuit evaluation takes effect and the `eq` comparison operator is not executed. The response header `USER-DEFINED-1` will not be set because the `and()` function returns a value of false.

or

Item	Description
Syntax	`or(arg, ...)`
Description	Executes the OR logical operator. Short-circuit evaluation is supported. When a value evaluates to true, the values that follow this value are not evaluated.
Parameter	The value that you want to check. You can specify one or more values. Data type: any type.
Return value	Returns `true` if a value evaluates to true and returns `false` if all values evaluate to false.
Example	`if and($http_from, or(eq($http_from, 'wap'), eq($http_from, 'comos'))) { rewrite(concat('http://tech.com.cn/zt_d/we2015/', $http_from), 'enhance_redirect') }` If the request includes the `from` header and its value is `[wap\|comos]`, the HTTP 302 status code is returned and the request is redirected to `http://tech.com.cn/zt_d/we2015/[wap\|comos]`. If the request includes the `from` header and its value is `wap`, the short-circuit evaluation takes effect and the `eq comos` value is ignored. The `or()` function returns a value of `true`.

not

Item	Description
Syntax	`not(arg)`
Description	Executes the NOT logical operator. The values of `undef` and `false` evaluate to false, and other values evaluate to true.
Parameter	The value that you want to check. You can specify only one value. Data type: any type.
Return value	true false
Example	`if not($arg_key) { exit(403) } if not($cookie_user) { exit(403, 'not cookie user') } if not(0) { exit(403) } if not(false) { exit(403) }` If a request does not include the `key` parameter, the request is denied and the HTTP 403 status code is returned. If a request does not include `cookie_user`, the request is denied. The HTTP 403 status code and the response body `"not cookie user"` are returned. The `not(0)` function returns a value of `false`. The `not(false)` function returns a value of `true`.

eq

Item	Description
Syntax	`eq(arg1, arg2)`
Description	Compares whether two values are equal.
Parameter	arg1: the first value to compare. Data type: any type. arg2: the second value to compare. Data type: same as the `arg1` parameter.
Return value	Returns `true` if the two values are equal and returns `false` if they are not equal.
Example	`key1 = 'value1' key2 = 'value2' if and($arg_k1, $arg_k2, eq(key1, $arg_k1), ne(key2, $arg_k2)) { say('match condition') }` If the request includes both the `k1` and `k2` parameters, the comparison operations are performed. If the request does not include the `k1` or `k2` parameter, the short-circuit evaluation takes effect and the comparison operations are not performed. `eq`: whether the value of the `k1` parameter is equal to `value1`. `ne`: whether the value of the `k2` parameter is not equal to `value2`. The response that contains the response body `match condition` is returned only if the following conditions are met: the request includes both the `k1` and `k2` parameters, the value of the `k1` parameter is equal to `value1`, and the value of the `k2` parameter is not equal to `value2`.

ne

Item	Description
Syntax	`ne(arg1, arg2)`
Description	Compares whether two values are not equal.
Parameter	arg1: the first value to compare. Data type: any type. arg2: the second value to compare. Data type: same as the `arg1` parameter.
Return value	Returns `true` if the two values are not equal and returns `false` if they are equal.
Example	`key1 = 'value1' key2 = 'value2' if and($arg_k1, $arg_k2, eq(key1, $arg_k1), ne(key2, $arg_k2)) { say('match condition') }` If the request includes both the `k1` and `k2` parameters, the comparison operations are performed. If the request does not include the `k1` or `k2` parameter, the short-circuit evaluation takes effect and the comparison operations are not performed. `eq`: whether the value of the `k1` parameter is equal to `value1`. `ne`: whether the value of the `k2` parameter is not equal to `value2`. The response that contains the response body `match condition` is returned only if the following conditions are met: the request includes both the `k1` and `k2` parameters, the value of the `k1` parameter is equal to `value1`, and the value of the `k2` parameter is not equal to `value2`.

null

Item	Description
Syntax	`null(v)`
Description	Checks whether a data type is specified for AScript.
Parameter	v: the parameter to pass. Data type: array, dictionary, or string. A value of false is returned for other data types.
Return value	Data type: Boolean. A value of true is returned if the value of v is an array or a dictionary. A value of true is returned if the value of v is an empty string. A value of false is returned if v is set to other data types.
Example	`d = [] say(null(d)) set(d, 1, 'v1') say(null(d)) say(tostring(null('x'))) say(tostring(null('')))` Output: `true false false true`