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1# System Parameter
2
3> **NOTE**<br>
4> - The initial APIs of this module are supported since API version 6. Newly added APIs will be marked with a superscript to indicate their earliest API version.
5> - This is a system API and cannot be called by third-party applications.
6
7## Modules to Import
8
9```ts
10import parameter from '@ohos.systemParameter'
11```
12
13
14## parameter.getSync
15
16getSync(key: string, def?: string): string
17
18Obtains the value of the attribute with the specified key.
19
20**System capability**: SystemCapability.Startup.SysInfo
21
22**Parameters**
23
24| Name| Type| Mandatory| Description|
25| -------- | -------- | -------- | -------- |
26| key | string | Yes| Key of the system attribute.|
27| def | string | No| Default value.|
28
29**Return value**
30
31| Type| Description|
32| -------- | -------- |
33| string | System attribute value. If the specified key does not exist, the default value is returned. If no default value has been set, an empty string will be returned.|
34
35**Example**
36
37```ts
38try {
39    var info = parameter.getSync("test.parameter.key");
40    console.log(JSON.stringify(info));
41}catch(e){
42    console.log("getSync unexpected error: " + e);
43}
44```
45
46
47## parameter.get
48
49get(key: string, callback: AsyncCallback&lt;string&gt;): void
50
51Obtains the value of the attribute with the specified key. This API uses an asynchronous callback to return the result.
52
53**System capability**: SystemCapability.Startup.SysInfo
54
55**Parameters**
56
57| Name| Type| Mandatory| Description|
58| -------- | -------- | -------- | -------- |
59| key | string | Yes| Key of the system attribute.|
60| callback | AsyncCallback&lt;string&gt; | Yes| Callback used to return the result.|
61
62**Example**
63
64```ts
65try {
66    parameter.get("test.parameter.key", function (err, data) {
67    if (err == undefined) {
68        console.log("get test.parameter.key value success:" + data)
69    } else {
70        console.log(" get test.parameter.key value err:" + err.code)
71    }});
72}catch(e){
73    console.log("get unexpected error: " + e);
74}
75```
76
77
78## parameter.get
79
80get(key: string, def: string, callback: AsyncCallback&lt;string&gt;): void
81
82Obtains the value of the attribute with the specified key. This API uses an asynchronous callback to return the result.
83
84**System capability**: SystemCapability.Startup.SysInfo
85
86**Parameters**
87
88| Name| Type| Mandatory| Description|
89| -------- | -------- | -------- | -------- |
90| key | string | Yes| Key of the system attribute.|
91| def | string | Yes| Default value.|
92| callback | AsyncCallback&lt;string&gt; | Yes| Callback used to return the result.|
93
94**Example**
95
96```ts
97try {
98    parameter.get("test.parameter.key", "default", function (err, data) {
99        if (err == undefined) {
100            console.log("get test.parameter.key value success:" + data)
101        } else {
102            console.log(" get test.parameter.key value err:" + err.code)
103        }
104    });
105}catch(e){
106    console.log("get unexpected error:" + e)
107}
108```
109
110
111## parameter.get
112
113get(key: string, def?: string): Promise&lt;string&gt;
114
115Obtains the value of the attribute with the specified key. This API uses a promise to return the result.
116
117**System capability**: SystemCapability.Startup.SysInfo
118
119**Parameters**
120
121| Name| Type| Mandatory| Description|
122| -------- | -------- | -------- | -------- |
123| key | string | Yes| Key of the system attribute.|
124| def | string | No| Default value.|
125
126**Return value**
127
128| Type| Description|
129| -------- | -------- |
130| Promise&lt;string&gt; | Promise used to return the execution result.|
131
132**Example**
133
134```ts
135try {
136    var p = parameter.get("test.parameter.key");
137    p.then(function (value) {
138        console.log("get test.parameter.key success: " + value);
139    }).catch(function (err) {
140        console.log("get test.parameter.key error: " + err.code);
141    });
142}catch(e){
143    console.log("get unexpected error: " + e);
144}
145```
146
147
148## parameter.setSync
149
150setSync(key: string, value: string): void
151
152Sets a value for the attribute with the specified key.
153
154**System capability**: SystemCapability.Startup.SysInfo
155
156**Parameters**
157
158| Name| Type| Mandatory| Description|
159| -------- | -------- | -------- | -------- |
160| key | string | Yes| Key of the system attribute.|
161| value | string | Yes| System attribute value to set.|
162
163**Example**
164
165```ts
166try {
167    parameter.setSync("test.parameter.key", "default");
168}catch(e){
169    console.log("set unexpected error: " + e);
170}
171```
172
173
174## parameter.set
175
176set(key: string, value: string, callback: AsyncCallback&lt;void&gt;): void
177
178Sets a value for the attribute with the specified key. This API uses an asynchronous callback to return the result.
179
180**System capability**: SystemCapability.Startup.SysInfo
181
182**Parameters**
183
184| Name| Type| Mandatory| Description|
185| -------- | -------- | -------- | -------- |
186| key | string | Yes| Key of the system attribute.|
187| value | string | Yes| System attribute value to set.|
188| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the result.|
189
190**Example**
191
192```ts
193try {
194    parameter.set("test.parameter.key", "testValue", function (err, data) {
195    if (err == undefined) {
196        console.log("set test.parameter.key value success :" + data)
197    } else {
198        console.log("set test.parameter.key value err:" + err.code)
199    }});
200}catch(e){
201    console.log("set unexpected error: " + e);
202}
203```
204
205
206## parameter.set
207
208set(key: string, value: string): Promise&lt;void&gt;
209
210Sets a value for the attribute with the specified key. This API uses a promise to return the result.
211
212**System capability**: SystemCapability.Startup.SysInfo
213
214**Parameters**
215
216| Name| Type| Mandatory| Description|
217| -------- | -------- | -------- | -------- |
218| key | string | Yes| Key of the system attribute.|
219| value| string | Yes | System attribute value to set.|
220
221**Return value**
222
223| Type| Description|
224| -------- | -------- |
225| Promise&lt;void&gt; | Promise used to return the execution result.|
226
227**Example**
228
229```ts
230try {
231    var p = para.set("test.parameter.key", "testValue");
232    p.then(function (value) {
233        console.log("set test.parameter.key success: " + value);
234    }).catch(function (err) {
235        console.log(" set test.parameter.key error: " + err.code);
236    });
237}catch(e){
238    console.log("set unexpected error: " + e);
239}
240```
241