@ohos.systemParameterEnhance (System Parameter) (System API)

The SystemParameter module provides system services with easy access to key-value pairs. You can use the APIs provided by this module to describe the service status and change the service behavior. The basic operation primitives are get and set. You can obtain the values of system parameters through getter APIs and modify the values through setter APIs. For details about the system parameter design principles and definitions, see Parameter Management.

NOTE

• The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.
• The APIs provided by this module are system APIs.
• Third-party applications cannot use the APIs provided by this module, because system parameters each require specific discretionary access control (DAC) and mandatory access control (MAC) permissions.

Modules to Import

import { systemParameterEnhance } from '@kit.BasicServicesKit';

systemParameterEnhance.getSync

getSync(key: string, def?: string): string

Obtains the value of the system parameter with the specified key.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
def	string	No	Default value of the system parameter. It works only when the system parameter does not exist. The value can be undefined or any custom value.

Return value

Type	Description
string	Value of the system parameter. If the specified key exists, the set value is returned. If the specified key does not exist and def is set to a valid value, the set value is returned. If the specified key does not exist and def is set to an invalid value (such as undefined) or is not set, an exception is thrown.

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700101	System parameter not found.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

try {
    let info: string = systemParameterEnhance.getSync("const.ohos.apiversion");
    console.log(JSON.stringify(info));
} catch(e) {
    console.log("getSync unexpected error: " + e);
}

systemParameterEnhance.get

get(key: string, callback: AsyncCallback<string>): void

Obtains the value of the system parameter with the specified key.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
callback	AsyncCallback<string>	Yes	Callback used to return the result.

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700101	System parameter not found.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

import { BusinessError } from '@kit.BasicServicesKit';

try {
    systemParameterEnhance.get("const.ohos.apiversion", (err: BusinessError, data: string) => {
    if (err == undefined) {
        console.log("get test.parameter.key value success:" + data)
    } else {
        console.log(" get test.parameter.key value err:" + err.code)
    }});
} catch(e) {
    console.log("get unexpected error: " + e);
}

systemParameterEnhance.get

get(key: string, def: string, callback: AsyncCallback<string>): void

Obtains the value of the system parameter with the specified key. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
def	string	Yes	Default value.
callback	AsyncCallback<string>	Yes	Callback used to return the result.

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700101	System parameter not found.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

import { BusinessError } from '@kit.BasicServicesKit';

try {
    systemParameterEnhance.get("const.ohos.apiversion", "default", (err: BusinessError, data: string) => {
        if (err == undefined) {
            console.log("get test.parameter.key value success:" + data)
        } else {
            console.log(" get test.parameter.key value err:" + err.code)
        }
    });
} catch(e) {
    console.log("get unexpected error:" + e)
}

systemParameterEnhance.get

get(key: string, def?: string): Promise<string>

Obtains the value of the system parameter with the specified key. This API uses a promise to return the result.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
def	string	No	Default value of the system parameter. It works only when the system parameter does not exist. The value can be undefined or any custom value.

Return value

Type	Description
Promise<string>	Promise used to return the execution result.

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700101	System parameter not found.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

import { BusinessError } from '@kit.BasicServicesKit';

try {
    let p: Promise<string> = systemParameterEnhance.get("const.ohos.apiversion");
    p.then((value: string) => {
        console.log("get test.parameter.key success: " + value);
    }).catch((err: BusinessError) => {
        console.log("get test.parameter.key error: " + err.code);
    });
} catch(e) {
    console.log("get unexpected error: " + e);
}

systemParameterEnhance.setSync

setSync(key: string, value: string): void

Sets a value for the system parameter with the specified key.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
value	string	Yes	Value of the system parameter to set. The value can contain a maximum of 96 bytes (including the end character).

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700102	Invalid system parameter value.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

import { BusinessError } from '@kit.BasicServicesKit';

try {
    systemParameterEnhance.setSync("test.parameter.key", "default");
} catch(e) {
    console.log("set unexpected error: " + e);
}

systemParameterEnhance.set

set(key: string, value: string, callback: AsyncCallback<void>): void

Sets a value for the system parameter with the specified key. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
value	string	Yes	Value of the system parameter to set. The value can contain a maximum of 96 bytes (including the end character).
callback	AsyncCallback<void>	Yes	Callback used to return the result.

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700102	Invalid system parameter value.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

import { BusinessError } from '@kit.BasicServicesKit';

try {
    systemParameterEnhance.set("test.parameter.key", "testValue", (err: BusinessError, data: void) => {
    if (err == undefined) {
        console.log("set test.parameter.key value success :" + data)
    } else {
        console.log("set test.parameter.key value err:" + err.code)
    }});
} catch(e) {
    console.log("set unexpected error: " + e);
}

systemParameterEnhance.set

set(key: string, value: string): Promise<void>

Sets a value for the system parameter with the specified key. This API uses a promise to return the result.

System capability: SystemCapability.Startup.SystemInfo

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the system parameter. The value can contain a maximum of 128 bytes. Only letters, digits, periods (.), hyphens (-), at signs (@), colons (:), and underscores (_) are allowed.
value	string	Yes	Value of the system parameter to set. The value can contain a maximum of 96 bytes (including the end character).

Return value

Type	Description
Promise<void>	Promise used to return the execution result.

Error codes

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified; 2.incorrect parameter types; 3.parameter verification failed.
14700102	Invalid system parameter value.
14700103	The operation on the system permission is denied.
14700104	System internal error such as out memory or deadlock.

For details about the error codes, see System Parameter Error Codes.

Example

import { BusinessError } from '@kit.BasicServicesKit';

try {
    let p: Promise<void>  = systemParameterEnhance.set("test.parameter.key", "testValue");
    p.then((value: void) => {
        console.log("set test.parameter.key success: " + value);
    }).catch((err: BusinessError) => {
        console.log(" set test.parameter.key error: " + err.code);
    });
} catch(e) {
    console.log("set unexpected error: " + e);
}

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