#鸿蒙学习大百科#如何阶段文件中的内容只剩下指定的长度的内容？

import { common } from '@kit.AbilityKit';
import fs from '@ohos.file.fs';
import { BusinessError } from '@kit.BasicServicesKit';
@Entry
@Component
struct Index {
  private context = getContext(this) as common.UIAbilityContext;
  build() {
    Row() {
      Column() {
        Text("Hello")
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
          .onClick(() => {
            let applicationContext = this.context.getApplicationContext();
            let cacheDir = applicationContext.cacheDir;
            let dirPath = cacheDir + "/aaa";
            fs.open(dirPath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE).then((file: fs.File) => {
              let len = 5//阶段后剩余的长度
              fs.truncate(file.fd,len, (err: BusinessError) => {
                if (err) {
                  console.error("read failed with error message: " + err.message + ", error code: " + err.code);
                } else {
                  console.info("truncate succeed");
                }
                fs.closeSync(file);
              })
            })
          })
      }
      .width('100%')
    }
    .height('100%')
  }
}