1# Single I/O Task Development 2 3 4Asynchronous concurrency provided by Promise and async/await is applicable to the development of a single I/O task. The following uses the asynchronous concurrency capability to write a file as an example. 5 6 71. Implement the logic of a single I/O task. 8 9 ```js 10 import fs from '@ohos.file.fs'; 11 12 async function write(data: string, filePath: string) { 13 let file = await fs.open(filePath, fs.OpenMode.READ_WRITE); 14 fs.write(file.fd, data).then((writeLen) => { 15 fs.close(file); 16 }).catch((err) => { 17 console.error(`Failed to write data. Code is ${err.code}, message is ${err.message}`); 18 }) 19 } 20 ``` 21 222. Use the asynchronous capability to invoke the single I/O task. For details about how to obtain **filePath** in the example, see [Obtaining Application File Paths](../application-models/application-context-stage.md#obtaining-application-file-paths). 23 24 ```js 25 let filePath = ...; // Application file path 26 write('Hello World!', filePath).then(() => { 27 console.info('Succeeded in writing data.'); 28 }) 29 ``` 30