@ohos.file.fs (File Management)

The fs module provides APIs for file operations, including accessing and manaing files and directories, obtaining file information statistics, and reading and writing data using a stream.

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.

Modules to Import

import fs from '@ohos.file.fs';

Guidelines

Before using the APIs provided by this module to perform operations on a file or directory, obtain the application sandbox path of the file or directory as follows:

import UIAbility from '@ohos.app.ability.UIAbility';
import window from '@ohos.window';

export default class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    let context = this.context;
    let pathDir = context.filesDir;
  }
}

For details about how to obtain the application sandbox path, see Obtaining Application File Paths.

fs.stat

stat(file: string | number): Promise<Stat>

Obtains detailed file attribute information. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.stat(filePath).then((stat: fs.Stat) => {
  console.info("get file info succeed, the size of file is " + stat.size);
}).catch((err: BusinessError) => {
  console.error("get file info failed with error message: " + err.message + ", error code: " + err.code);
});

fs.stat

stat(file: string | number, callback: AsyncCallback<Stat>): void

Obtains detailed file information. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
fs.stat(pathDir, (err: BusinessError, stat: fs.Stat) => {
  if (err) {
    console.error("get file info failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("get file info succeed, the size of file is " + stat.size);
  }
});

fs.statSync

statSync(file: string | number): Stat

Obtains detailed file information. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let stat = fs.statSync(pathDir);
console.info("get file info succeed, the size of file is " + stat.size);

fs.access

access(path: string): Promise<boolean>

Checks whether a file exists. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.access(filePath).then((res: boolean) => {
  if (res) {
    console.info("file exists");
  } else {
    console.info("file not exists");
  }
}).catch((err: BusinessError) => {
  console.error("access failed with error message: " + err.message + ", error code: " + err.code);
});

fs.access

access(path: string, callback: AsyncCallback<boolean>): void

Checks whether a file exists. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.access(filePath, (err: BusinessError, res: boolean) => {
  if (err) {
    console.error("access failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    if (res) {
      console.info("file exists");
    } else {
      console.info("file not exists");
    }
  }
});

fs.accessSync

accessSync(path: string): boolean

Checks whether a file exists. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
try {
  let res = fs.accessSync(filePath);
  if (res) {
    console.info("file exists");
  } else {
    console.info("file not exists");
  }
} catch(error) {
  let err: BusinessError = error as BusinessError;
  console.error("accessSync failed with error message: " + err.message + ", error code: " + err.code);
}

fs.close

close(file: number | File): Promise<void>

Closes a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.close(file).then(() => {
  console.info("File closed");
}).catch((err: BusinessError) => {
  console.error("close file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.close

close(file: number | File, callback: AsyncCallback<void>): void

Closes a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.close(file, (err: BusinessError) => {
  if (err) {
    console.error("close file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("File closed");
  }
});

fs.closeSync

closeSync(file: number | File): void

Closes a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.closeSync(file);

fs.copyFile

copyFile(src: string | number, dest: string | number, mode?: number): Promise<void>

Copies a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcPath = pathDir + "/srcDir/test.txt";
let dstPath = pathDir + "/dstDir/test.txt";
fs.copyFile(srcPath, dstPath).then(() => {
  console.info("copy file succeed");
}).catch((err: BusinessError) => {
  console.error("copy file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.copyFile

copyFile(src: string | number, dest: string | number, mode: number, callback: AsyncCallback<void>): void

Copies a file with the specified mode. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcPath = pathDir + "/srcDir/test.txt";
let dstPath = pathDir + "/dstDir/test.txt";
fs.copyFile(srcPath, dstPath, 0, (err: BusinessError) => {
  if (err) {
    console.error("copy file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("copy file succeed");
  }
});

fs.copyFile

copyFile(src: string | number, dest: string | number, callback: AsyncCallback<void>): void

Copies a file. This API overwrites the file with the same name in the destination directory and truncates the part that is not overwritten. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcPath = pathDir + "/srcDir/test.txt";
let dstPath = pathDir + "/dstDir/test.txt";
fs.copyFile(srcPath, dstPath, (err: BusinessError) => {
  if (err) {
    console.error("copy file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("copy file succeed");
  }
});

fs.copyFileSync

copyFileSync(src: string | number, dest: string | number, mode?: number): void

Copies a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let srcPath = pathDir + "/srcDir/test.txt";
let dstPath = pathDir + "/dstDir/test.txt";
fs.copyFileSync(srcPath, dstPath);

fs.copyDir¹⁰⁺

copyDir(src: string, dest: string, mode?: number): Promise<void>

Copies a folder. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
// Copy srcPath to destPath.
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
fs.copyDir(srcPath, destPath, 0).then(() => {
  console.info("copy directory succeed");
}).catch((err: BusinessError<Array<ConflictFiles>>) => {
  if (err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("copy directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else (err) {
    console.error("copy directory failed with error message: " + err.message + ", error code: " + err.code);
  }
});

fs.copyDir¹⁰⁺

copyDir(src: string, dest: string, mode: number, callback: AsyncCallback<void, Array<ConflictFiles>>): void

Copies a folder with the specified mode. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { ConflictFiles } from '@ohos.file.fs';
// Copy srcPath to destPath.
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
fs.copyDir(srcPath, destPath, 0, (err: BusinessError<Array<ConflictFiles>>) => {
  if (err && err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("copy directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else if (err) {
    console.error("copy directory failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("copy directory succeed");
  }  
});

fs.copyDir¹⁰⁺

copyDir(src: string, dest: string, callback: AsyncCallback<void, Array<ConflictFiles>>): void

Copies a folder. This API uses an asynchronous callback to return the result.

An exception will be thrown if there is a folder with the same name in the destination directory and there are files with the same name in the conflicting folder. All the non-conflicting files in the source folder will be moved to the destination folder, and the non-conflicting files in the destination folder will be retained. The data attribute in the error returned provides information about the conflicting files in the Array<ConflictFiles> format.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { ConflictFiles } from '@ohos.file.fs';
// Copy srcPath to destPath.
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
fs.copyDir(srcPath, destPath, (err: BusinessError<Array<ConflictFiles>>) => {
  if (err && err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("copy directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else if (err) {
    console.error("copy directory failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("copy directory succeed");
  }  
});

fs.copyDirSync¹⁰⁺

copyDirSync(src: string, dest: string, mode?: number): void

Copies a folder. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { ConflictFiles } from '@ohos.file.fs';
// Copy srcPath to destPath.
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
try {
  fs.copyDirSync(srcPath, destPath, 0);
  console.info("copy directory succeed");
} catch (error) {
  let err: BusinessError<Array<ConflictFiles>> = error as BusinessError<Array<ConflictFiles>>;
  if (err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("copy directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else {
    console.error("copy directory failed with error message: " + err.message + ", error code: " + err.code);
  }
}

fs.dup¹⁰⁺

dup(fd: number): File

Opens a File object based on an FD.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

// convert fd to file
let fd: number = 0;  // fd comes from other modules
let file = fs.dup(fd);
console.info("The name of the file is " + file.name);
fs.closeSync(file);

fs.mkdir

mkdir(path: string): Promise<void>

Creates a directory. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let dirPath = pathDir + "/testDir";
fs.mkdir(dirPath).then(() => {
  console.info("Directory created");
}).catch((err: BusinessError) => {
  console.error("mkdir failed with error message: " + err.message + ", error code: " + err.code);
});

fs.mkdir

mkdir(path: string, callback: AsyncCallback<void>): void

Creates a directory. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let dirPath = pathDir + "/testDir";
fs.mkdir(dirPath, (err: BusinessError) => {
  if (err) {
    console.error("mkdir failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Directory created");
  }
});

fs.mkdirSync

mkdirSync(path: string): void

Creates a directory. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let dirPath = pathDir + "/testDir";
fs.mkdirSync(dirPath);

fs.open

open(path: string, mode?: number): Promise<File>

Opens a file. This API uses a promise to return the result. The uniform resource identifier (URI) can be used to open a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.open(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE).then((file: fs.File) => {
  console.info("file fd: " + file.fd);
  fs.closeSync(file);
}).catch((err: BusinessError) => {
  console.error("open file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.open

open(path: string, mode: number, callback: AsyncCallback<File>): void

Opens a file with the specified mode. This API uses an asynchronous callback to return the result.

File URIs are supported.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.open(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE, (err: BusinessError, file: fs.File) => {
  if (err) {
    console.error("open failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("file fd: " + file.fd);
  }
  fs.closeSync(file);
});

fs.open

open(path: string, callback: AsyncCallback<File>): void

Opens a file in read-only mode. This API uses an asynchronous callback to return the result.

File URIs are supported.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.open(filePath, (err: BusinessError, file: fs.File) => {
  if (err) {
    console.error("open failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("file fd: " + file.fd);
  }
  fs.closeSync(file);
});

fs.openSync

openSync(path: string, mode?: number): File

Opens a file. This API returns the result synchronously. File URIs are supported.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
console.info("file fd: " + file.fd);
fs.closeSync(file);

fs.read

read(fd: number, buffer: ArrayBuffer, options?: { offset?: number; length?: number; }): Promise<number>

Reads data from a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import buffer from '@ohos.buffer';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE);
let arrayBuffer = new ArrayBuffer(4096);
fs.read(file.fd, arrayBuffer).then((readLen: number) => {
  console.info("Read file data successfully");
  let buf = buffer.from(arrayBuffer, 0, readLen);
  console.info(`The content of file: ${buf.toString()}`);
}).catch((err: BusinessError) => {
  console.error("read file data failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  fs.closeSync(file);
});

fs.read

read(fd: number, buffer: ArrayBuffer, options?: { offset?: number; length?: number; }, callback: AsyncCallback<number>): void

Reads data from a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import buffer from '@ohos.buffer';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE);
let arrayBuffer = new ArrayBuffer(4096);
fs.read(file.fd, arrayBuffer, (err: BusinessError, readLen: number) => {
  if (err) {
    console.error("read failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Read file data successfully");
    let buf = buffer.from(arrayBuffer, 0, readLen);
    console.info(`The content of file: ${buf.toString()}`);
  }
  fs.closeSync(file);
});

fs.readSync

readSync(fd: number, buffer: ArrayBuffer, options?: { offset?: number; length?: number; }): number

Reads data from a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE);
let buf = new ArrayBuffer(4096);
fs.readSync(file.fd, buf);
fs.closeSync(file);

fs.rmdir

rmdir(path: string): Promise<void>

Deletes a directory. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let dirPath = pathDir + "/testDir";
fs.rmdir(dirPath).then(() => {
  console.info("Directory deleted");
}).catch((err: BusinessError) => {
  console.error("rmdir failed with error message: " + err.message + ", error code: " + err.code);
});

fs.rmdir

rmdir(path: string, callback: AsyncCallback<void>): void

Deletes a directory. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let dirPath = pathDir + "/testDir";
fs.rmdir(dirPath, (err: BusinessError) => {
  if (err) {
    console.error("rmdir failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Directory deleted");
  }
});

fs.rmdirSync

rmdirSync(path: string): void

Deletes a directory. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let dirPath = pathDir + "/testDir";
fs.rmdirSync(dirPath);

fs.unlink

unlink(path: string): Promise<void>

Deletes a single file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.unlink(filePath).then(() => {
  console.info("File deleted");
}).catch((err: BusinessError) => {
  console.error("remove file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.unlink

unlink(path: string, callback: AsyncCallback<void>): void

Deletes a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.unlink(filePath, (err: BusinessError) => {
  if (err) {
    console.error("remove file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("File deleted");
  }
});

fs.unlinkSync

unlinkSync(path: string): void

Deletes a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
fs.unlinkSync(filePath);

fs.write

write(fd: number, buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }): Promise<number>

Writes data to a file. This API uses a promise to return the data.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
let str: string = "hello, world";
fs.write(file.fd, str).then((writeLen: number) => {
  console.info("write data to file succeed and size is:" + writeLen);
}).catch((err: BusinessError) => {
  console.error("write data to file failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  fs.closeSync(file);
});

fs.write

write(fd: number, buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }, callback: AsyncCallback<number>): void

Writes data to a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
let str: string = "hello, world";
fs.write(file.fd, str, (err: BusinessError, writeLen: number) => {
  if (err) {
    console.error("write data to file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("write data to file succeed and size is:" + writeLen);
  }
  fs.closeSync(file);
});

fs.writeSync

writeSync(fd: number, buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }): number

Writes data to a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
let str: string = "hello, world";
let writeLen = fs.writeSync(file.fd, str);
console.info("write data to file succeed and size is:" + writeLen);
fs.closeSync(file);

fs.truncate

truncate(file: string | number, len?: number): Promise<void>

Truncates a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let len: number = 5;
fs.truncate(filePath, len).then(() => {
  console.info("File truncated");
}).catch((err: BusinessError) => {
  console.error("truncate file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.truncate

truncate(file: string | number, len?: number, callback: AsyncCallback<void>): void

Truncates a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let len: number = 5;
fs.truncate(filePath, len, (err: BusinessError) => {
  if (err) {
    console.error("truncate failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("truncate succeed");
  }
});

fs.truncateSync

truncateSync(file: string | number, len?: number): void

Truncates a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let len: number = 5;
fs.truncateSync(filePath, len);

fs.readText

readText(filePath: string, options?: { offset?: number; length?: number; encoding?: string; }): Promise<string>

Reads the text content of a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.readText(filePath).then((str: string) => {
  console.info("readText succeed:" + str);
}).catch((err: BusinessError) => {
  console.error("readText failed with error message: " + err.message + ", error code: " + err.code);
});

fs.readText

readText(filePath: string, options?: { offset?: number; length?: number; encoding?: string; }, callback: AsyncCallback<string>): void

Reads the text content of a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let stat = fs.statSync(filePath);
let option = new Option();
option.offset = 1;
option.length = stat.size;
fs.readText(filePath, option, (err: BusinessError, str: string) => {
  if (err) {
    console.error("readText failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("readText succeed:" + str);
  }
});

fs.readTextSync

readTextSync(filePath: string, options?: { offset?: number; length?: number; encoding?: string; }): string

Reads the text of a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let stat = fs.statSync(filePath);
let option = new Option();
option.offset = 1;
option.length = stat.size;
let str = fs.readTextSync(filePath, option);
console.info("readText succeed:" + str);

fs.lstat

lstat(path: string): Promise<Stat>

Obtains information about a symbolic link that is used to refer to a file or directory. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/linkToFile";
fs.lstat(filePath).then((stat: fs.Stat) => {
  console.info("lstat succeed, the size of file is " + stat.size);
}).catch((err: BusinessError) => {
  console.error("lstat failed with error message: " + err.message + ", error code: " + err.code);
});

fs.lstat

lstat(path: string, callback: AsyncCallback<Stat>): void

Obtains information about a symbolic link that is used to refer to a file or directory. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/linkToFile";
fs.lstat(filePath, (err: BusinessError, stat: fs.Stat) => {
  if (err) {
    console.error("lstat failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("lstat succeed, the size of file is " + stat.size);
  }
});

fs.lstatSync

lstatSync(path: string): Stat

Obtains information about a symbolic link that is used to refer to a file or directory. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/linkToFile";
fs.lstatSync(filePath);

fs.rename

rename(oldPath: string, newPath: string): Promise<void>

Renames a file or folder. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcFile = pathDir + "/test.txt";
let dstFile = pathDir + "/new.txt";
fs.rename(srcFile, dstFile).then(() => {
  console.info("File renamed");
}).catch((err: BusinessError) => {
  console.error("rename failed with error message: " + err.message + ", error code: " + err.code);
});

fs.rename

rename(oldPath: string, newPath: string, callback: AsyncCallback<void>): void

Renames a file or folder. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcFile = pathDir + "/test.txt";
let dstFile = pathDir + "/new.txt";
fs.rename(srcFile, dstFile, (err: BusinessError) => {
  if (err) {
    console.error("rename failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("File renamed");
  }
});

fs.renameSync

renameSync(oldPath: string, newPath: string): void

Renames a file or folder. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let srcFile = pathDir + "/test.txt";
let dstFile = pathDir + "/new.txt";
fs.renameSync(srcFile, dstFile);

fs.fsync

fsync(fd: number): Promise<void>

Synchronizes a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fsync(file.fd).then(() => {
  console.info("Data flushed");
}).catch((err: BusinessError) => {
  console.error("sync data failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  fs.closeSync(file);
});

fs.fsync

fsync(fd: number, callback: AsyncCallback<void>): void

Synchronizes a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fsync(file.fd, (err: BusinessError) => {
  if (err) {
    console.error("fsync failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("fsync succeed");
  }
  fs.closeSync(file);
});

fs.fsyncSync

fsyncSync(fd: number): void

Synchronizes a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fsyncSync(file.fd);
fs.closeSync(file);

fs.fdatasync

fdatasync(fd: number): Promise<void>

Synchronizes the data of a file. This API uses a promise to return the result. fdatasync() is similar to fsync(), but does not flush modified metadata unless that metadata is needed.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fdatasync(file.fd).then(() => {
  console.info("Data flushed");
}).catch((err: BusinessError) => {
  console.error("sync data failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  fs.closeSync(file);
});

fs.fdatasync

fdatasync(fd: number, callback: AsyncCallback<void>): void

Synchronizes the data of a file. This API uses an asynchronous callback to return the result. fdatasync() is similar to fsync(), but does not flush modified metadata unless that metadata is needed.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fdatasync (file.fd, (err: BusinessError) => {
  if (err) {
    console.error("fdatasync failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("fdatasync succeed");
  }
  fs.closeSync(file);
});

fs.fdatasyncSync

fdatasyncSync(fd: number): void

Synchronizes the data of a file. This API returns the result synchronously. fdatasync() is similar to fsync(), but does not flush modified metadata unless that metadata is needed.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fdatasyncSync(file.fd);
fs.closeSync(file);

fs.symlink

symlink(target: string, srcPath: string): Promise<void>

Creates a symbolic link based on a file path. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcFile = pathDir + "/test.txt";
let dstFile = pathDir + "/test";
fs.symlink(srcFile, dstFile).then(() => {
  console.info("Symbolic link created");
}).catch((err: BusinessError) => {
  console.error("symlink failed with error message: " + err.message + ", error code: " + err.code);
});

fs.symlink

symlink(target: string, srcPath: string, callback: AsyncCallback<void>): void

Creates a symbolic link based on a file path. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcFile = pathDir + "/test.txt";
let dstFile = pathDir + "/test";
fs.symlink(srcFile, dstFile, (err: BusinessError) => {
  if (err) {
    console.error("symlink failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Symbolic link created");
  }
});

fs.symlinkSync

symlinkSync(target: string, srcPath: string): void

Creates a symbolic link based on a file path. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let srcFile = pathDir + "/test.txt";
let dstFile = pathDir + "/test";
fs.symlinkSync(srcFile, dstFile);

fs.listFile

listFile(path: string, options?: { recursion?: boolean; listNum?: number; filter?: Filter; }): Promise<string[]>

Lists all files, including the files in subfolders, in a directory. This API uses a promise to return the result.
You can also set a filter to list the files you want.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

options parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { Filter } from '@ohos.file.fs';
class ListFileOption {
  public recursion: boolean = false;
  public listNum: number = 0;
  public filter: Filter = {};
}
let option = new ListFileOption();
option.filter.suffix = [".png", ".jpg", ".jpeg"];
option.filter.displayName = ["*abc", "efg*"];
option.filter.fileSizeOver = 1024;
option.filter.lastModifiedAfter = new Date().getTime();
fs.listFile(pathDir, option).then((filenames: Array<string>) => {
  console.info("listFile succeed");
  for (let i = 0; i < filenames.length; i++) {
    console.info("fileName: %s", filenames[i]);
  }
}).catch((err: BusinessError) => {
  console.error("list file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.listFile

listFile(path: string, options?: { recursion?: boolean; listNum?: number; filter?: Filter; }, callback: AsyncCallback<string[]>): void

Lists all files, including the files in subfolders, in a directory. This API uses an asynchronous callback to return the result.
You can also set a filter to list the files you want.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

options parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { Filter } from '@ohos.file.fs';
class ListFileOption {
  public recursion: boolean = false;
  public listNum: number = 0;
  public filter: Filter = {};
}
let option = new ListFileOption();
option.filter.suffix = [".png", ".jpg", ".jpeg"];
option.filter.displayName = ["*abc", "efg*"];
option.filter.fileSizeOver = 1024;
option.filter.lastModifiedAfter = new Date().getTime();
fs.listFile(pathDir, option, (err: BusinessError, filenames: Array<string>) => {
  if (err) {
    console.error("list file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("listFile succeed");
    for (let i = 0; i < filenames.length; i++) {
      console.info("filename: %s", filenames[i]);
    }
  }
});

fs.listFileSync

listFileSync(path: string, options?: { recursion?: boolean; listNum?: number; filter?: Filter; }): string[]

Lists all files, including the files in subfolders, in a directory. This API returns the result synchronously.
You can also set a filter to list the files you want.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

options parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import fs, { Filter } from '@ohos.file.fs';
class ListFileOption {
  public recursion: boolean = false;
  public listNum: number = 0;
  public filter: Filter = {};
}
let option = new ListFileOption();
option.filter.suffix = [".png", ".jpg", ".jpeg"];
option.filter.displayName = ["*abc", "efg*"];
option.filter.fileSizeOver = 1024;
option.filter.lastModifiedAfter = new Date().getTime();
let filenames = fs.listFileSync(pathDir, option);
console.info("listFile succeed");
for (let i = 0; i < filenames.length; i++) {
  console.info("filename: %s", filenames[i]);
}

fs.moveDir¹⁰⁺

moveDir(src: string, dest: string, mode?: number): Promise<void>

Moves a folder. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
// move directory from srcPath to destPath
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
fs.moveDir(srcPath, destPath, 1).then(() => {
  console.info("move directory succeed");
}).catch((err: BusinessError<Array<ConflictFiles>) => {
  if (err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("copy directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else(err) {
    console.error("copy directory failed with error message: " + err.message + ", error code: " + err.code);
  }
});

fs.moveDir¹⁰⁺

moveDir(src: string, dest: string, mode: number, callback: AsyncCallback<void, Array<ConflictFiles>>): void

Moves a folder with the specified mode. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { ConflictFiles } from '@ohos.file.fs';
// move directory from srcPath to destPath
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
fs.moveDir(srcPath, destPath, 1, (err: BusinessError<Array<ConflictFiles>>) => {
  if (err && err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("move directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else if (err) {
    console.error("move directory failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("move directory succeed");
  }  
});

fs.moveDir¹⁰⁺

moveDir(src: string, dest: string, callback: AsyncCallback<void, Array<ConflictFiles>>): void

Moves a folder. This API uses an asynchronous callback to return the result.

An exception will be thrown if there is a folder with the same name in the destination directory.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { ConflictFiles } from '@ohos.file.fs';
// move directory from srcPath to destPath
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
fs.moveDir(srcPath, destPath, (err: BusinessError<Array<ConflictFiles>>) => {
  if (err && err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("move directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else if (err) {
    console.error("move directory failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("move directory succeed");
  }  
});

fs.moveDirSync¹⁰⁺

moveDirSync(src: string, dest: string, mode?: number): void

Moves a folder. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import fs, { ConflictFiles } from '@ohos.file.fs';
// move directory from srcPath to destPath
let srcPath = pathDir + "/srcDir/";
let destPath = pathDir + "/destDir/";
try {
  fs.moveDirSync(srcPath, destPath, 1);
  console.info("move directory succeed");
} catch (error) {
  let err: BusinessError<Array<ConflictFiles>> = error as BusinessError<Array<ConflictFiles>>;
  if (err.code == 13900015) {
    for (let i = 0; i < err.data.length; i++) {
      console.error("move directory failed with conflicting files: " + err.data[i].srcFile + " " + err.data[i].destFile);
    }
  } else {
    console.error("move directory failed with error message: " + err.message + ", error code: " + err.code);
  }
}

fs.moveFile

moveFile(src: string, dest: string, mode?: number): Promise<void>

Moves a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcPath = pathDir + "/source.txt";
let destPath = pathDir + "/dest.txt";
fs.moveFile(srcPath, destPath, 0).then(() => {
  console.info("move file succeed");
}).catch((err: BusinessError) => {
  console.error("move file failed with error message: " + err.message + ", error code: " + err.code);
});

fs.moveFile

moveFile(src: string, dest: string, mode: number, callback: AsyncCallback<void>): void

Moves a file with the specified mode. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcPath = pathDir + "/source.txt";
let destPath = pathDir + "/dest.txt";
fs.moveFile(srcPath, destPath, 0, (err: BusinessError) => {
  if (err) {
    console.error("move file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("move file succeed");
  }  
});

fs.moveFile

moveFile(src: string, dest: string, callback: AsyncCallback<void>): void

Moves a file and forcibly overwrites the file with the same name in the destination directory. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let srcPath = pathDir + "/source.txt";
let destPath = pathDir + "/dest.txt";
fs.moveFile(srcPath, destPath, (err: BusinessError) => {
  if (err) {
    console.error("move file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("move file succeed");
  }  
});

fs.moveFileSync

moveFileSync(src: string, dest: string, mode?: number): void

Moves a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let srcPath = pathDir + "/source.txt";
let destPath = pathDir + "/dest.txt";
fs.moveFileSync(srcPath, destPath, 0);
console.info("move file succeed");

fs.mkdtemp

mkdtemp(prefix: string): Promise<string>

Creates a temporary directory. The folder name is created by replacing a string (specified by prefix) with six randomly generated characters. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
fs.mkdtemp(pathDir + "/XXXXXX").then((dir: string) => {
  console.info("mkdtemp succeed:" + dir);
}).catch((err: BusinessError) => {
  console.error("mkdtemp failed with error message: " + err.message + ", error code: " + err.code);
});

fs.mkdtemp

mkdtemp(prefix: string, callback: AsyncCallback<string>): void

Creates a temporary directory. The folder name is created by replacing a string (specified by prefix) with six randomly generated characters. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
fs.mkdtemp(pathDir + "/XXXXXX", (err: BusinessError, res: string) => {
  if (err) {
    console.error("mkdtemp failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("mkdtemp succeed");
  }
});

fs.mkdtempSync

mkdtempSync(prefix: string): string

Creates a temporary directory. The folder name is created by replacing a string (specified by prefix) with six randomly generated characters. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let res = fs.mkdtempSync(pathDir + "/XXXXXX");

fs.createRandomAccessFile¹⁰⁺

createRandomAccessFile(file: string | File, mode?: number): Promise<RandomAccessFile>

Creates a RandomAccessFile instance based on a file path or file object. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
fs.createRandomAccessFile(file).then((randomAccessFile: fs.RandomAccessFile) => {
  console.info("randomAccessFile fd: " + randomAccessFile.fd);
  randomAccessFile.close();
}).catch((err: BusinessError) => {
  console.error("create randomAccessFile failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  fs.closeSync(file);
});

fs.createRandomAccessFile¹⁰⁺

createRandomAccessFile(file: string | File, mode: number, callback: AsyncCallback<RandomAccessFile>): void

Creates a RandomAccessFile instance based on a file path or object. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
fs.createRandomAccessFile(file, fs.OpenMode.READ_WRITE, (err: BusinessError, randomAccessFile: fs.RandomAccessFile) => {
  if (err) {
    console.error("create randomAccessFile failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("randomAccessFile fd: " + randomAccessFile.fd);
    randomAccessFile.close();
  }
  fs.closeSync(file);
});

fs.createRandomAccessFile¹⁰⁺

createRandomAccessFile(file: string | File, callback: AsyncCallback<RandomAccessFile>): void

Creates a RandomAccessFile instance in read-only mode based on a file path or file object. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
fs.createRandomAccessFile(file, (err: BusinessError, randomAccessFile: fs.RandomAccessFile) => {
  if (err) {
    console.error("create randomAccessFile failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("randomAccessFile fd: " + randomAccessFile.fd);
    randomAccessFile.close();
  }
  fs.closeSync(file);
});

fs.createRandomAccessFileSync¹⁰⁺

createRandomAccessFileSync(file: string | File, mode?: number): RandomAccessFile

Creates a RandomAccessFile instance based on a file path or file object.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
let randomAccessFile = fs.createRandomAccessFileSync(file);
randomAccessFile.close();

fs.createStream

createStream(path: string, mode: string): Promise<Stream>

Creates a stream based on a file path. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.createStream(filePath, "a+").then((stream: fs.Stream) => {
  console.info("Stream created");
  stream.closeSync();
}).catch((err: BusinessError) => {
  console.error("createStream failed with error message: " + err.message + ", error code: " + err.code);
});

fs.createStream

createStream(path: string, mode: string, callback: AsyncCallback<Stream>): void

Creates a stream based on a file path. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
fs.createStream(filePath, "r+", (err: BusinessError, stream: fs.Stream) => {
  if (err) {
    console.error("createStream failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Stream created");
  }
  stream.closeSync();
});

fs.createStreamSync

createStreamSync(path: string, mode: string): Stream

Creates a stream based on a file path. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
console.info("Stream created");
stream.closeSync();

fs.fdopenStream

fdopenStream(fd: number, mode: string): Promise<Stream>

Opens a stream based on an FD. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath);
fs.fdopenStream(file.fd, "r+").then((stream: fs.Stream) => {
  console.info("Stream opened");
  fs.closeSync(file);
}).catch((err: BusinessError) => {
  console.error("openStream failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  stream.closeSync();
});

fs.fdopenStream

fdopenStream(fd: number, mode: string, callback: AsyncCallback<Stream>): void

Opens a stream based on an FD. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_ONLY);
fs.fdopenStream(file.fd, "r+", (err: BusinessError, stream: fs.Stream) => {
  if (err) {
    console.error("fdopen stream failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("fdopen stream succeed");
    fs.closeSync(file);
  }
  stream.closeSync();
});

fs.fdopenStreamSync

fdopenStreamSync(fd: number, mode: string): Stream

Opens a stream based on an FD. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_ONLY | fs.OpenMode.CREATE);
let stream = fs.fdopenStreamSync(file.fd, "r+");
fs.closeSync(file);
stream.closeSync();

fs.createWatcher¹⁰⁺

createWatcher(path: string, events: number, listener: WatchEventListener): Watcher

Creates a Watcher object to observe file or directory changes.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import fs, { WatchEvent } from '@ohos.file.fs';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
let watcher = fs.createWatcher(filePath, 0x2 | 0x10, (watchEvent: WatchEvent) => {
  if (watchEvent.event == 0x2) {
    console.info(watchEvent.fileName + 'was modified');
  } else if (watchEvent.event == 0x10) {
    console.info(watchEvent.fileName + 'was closed');
  }
});
watcher.start();
fs.writeSync(file.fd, 'test');
fs.closeSync(file);
watcher.stop();

WatchEventListener¹⁰⁺

(event: WatchEvent): void

Called when an observed event occurs.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

WatchEvent¹⁰⁺

Defines the event to observe.

System capability: SystemCapability.FileManagement.File.FileIO

Attributes

Stat

Represents detailed file information. Before calling any API of the Stat() class, use stat() to create a Stat instance.

System capability: SystemCapability.FileManagement.File.FileIO

Attributes

isBlockDevice

isBlockDevice(): boolean

Checks whether this file is a block special file. A block special file supports access by block only, and it is cached when accessed.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let isBLockDevice = fs.statSync(filePath).isBlockDevice();

isCharacterDevice

isCharacterDevice(): boolean

Checks whether this file is a character special file. A character special file supports random access, and it is not cached when accessed.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let isCharacterDevice = fs.statSync(filePath).isCharacterDevice();

isDirectory

isDirectory(): boolean

Checks whether this file is a directory.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let dirPath = pathDir + "/test";
let isDirectory = fs.statSync(dirPath).isDirectory(); 

isFIFO

isFIFO(): boolean

Checks whether this file is a named pipe (or FIFO). Named pipes are used for inter-process communication.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let isFIFO = fs.statSync(filePath).isFIFO(); 

isFile

isFile(): boolean

Checks whether this file is a regular file.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let isFile = fs.statSync(filePath).isFile();

isSocket

isSocket(): boolean

Checks whether this file is a socket.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let isSocket = fs.statSync(filePath).isSocket(); 

isSymbolicLink

isSymbolicLink(): boolean

Checks whether this file is a symbolic link.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test";
let isSymbolicLink = fs.statSync(filePath).isSymbolicLink(); 

Stream

Provides API for stream operations. Before calling any API of Stream, you need to create a Stream instance by using fs.createStream or fs.fdopenStream.

close

close(): Promise<void>

Closes this stream. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
stream.close().then(() => {
  console.info("File stream closed");
}).catch((err: BusinessError) => {
  console.error("close fileStream  failed with error message: " + err.message + ", error code: " + err.code);
});

close

close(callback: AsyncCallback<void>): void

Closes this stream. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
stream.close((err: BusinessError) => {
  if (err) {
    console.error("close stream failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("close stream succeed");
  }
});

closeSync

closeSync(): void

Closes this stream. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
stream.closeSync();

flush

flush(): Promise<void>

Flushes this stream. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
stream.flush().then(() => {
  console.info("Stream flushed");
  stream.close();
}).catch((err: BusinessError) => {
  console.error("flush failed with error message: " + err.message + ", error code: " + err.code);
});

flush

flush(callback: AsyncCallback<void>): void

Flushes this stream. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
stream.flush((err: BusinessError) => {
  if (err) {
    console.error("flush stream failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Stream flushed");
  }
  stream.close();
});

flushSync

flushSync(): void

Flushes this stream. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
stream.flushSync();
stream.close();

write

write(buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }): Promise<number>

Writes data to this stream. This API uses a promise to return the data.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let option = new Option();
option.offset = 5;
option.length = 5;
stream.write("hello, world", option).then((number: number) => {
  console.info("write succeed and size is:" + number);
  stream.close();
}).catch((err: BusinessError) => {
  console.error("write failed with error message: " + err.message + ", error code: " + err.code);
});

write

write(buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }, callback: AsyncCallback<number>): void

Writes data to this stream. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let option = new Option();
option.offset = 5;
option.length = 5;
stream.write("hello, world", option, (err: BusinessError, bytesWritten: number) => {
  if (err) {
    console.error("write stream failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    if (bytesWritten) {
      console.info("write succeed and size is:" + bytesWritten);
      stream.close();
    }
  }
});

writeSync

writeSync(buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }): number

Writes data to this stream. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let option = new Option();
option.offset = 5;
option.length = 5;
let num = stream.writeSync("hello, world", option);
stream.close();

read

read(buffer: ArrayBuffer, options?: { offset?: number; length?: number; }): Promise<number>

Reads data from this stream. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import buffer from '@ohos.buffer';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
let arrayBuffer = new ArrayBuffer(4096);
class Option {
  offset: number = 0;
  length: number = 0;
}
let option = new Option();
option.offset = 5;
option.length = 5;
stream.read(arrayBuffer, option).then((readLen: number) => {
  console.info("Read data successfully");
  let buf = buffer.from(arrayBuffer, 0, readLen);
  console.log(`The content of file: ${buf.toString()}`);
  stream.close();
}).catch((err: BusinessError) => {
  console.error("read data failed with error message: " + err.message + ", error code: " + err.code);
});

read

read(buffer: ArrayBuffer, options?: { position?: number; offset?: number; length?: number; }, callback: AsyncCallback<number>): void

Reads data from this stream. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
import buffer from '@ohos.buffer';
let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
let arrayBuffer = new ArrayBuffer(4096);
class Option {
  offset: number = 0;
  length: number = 0;
}
let option = new Option();
option.offset = 5;
option.length = 5;
stream.read(arrayBuffer, option, (err: BusinessError, readLen: number) => {
  if (err) {
    console.error("read stream failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("Read data successfully");
    let buf = buffer.from(arrayBuffer, 0, readLen);
    console.log(`The content of file: ${buf.toString()}`);
  }
  stream.close();
});

readSync

readSync(buffer: ArrayBuffer, options?: { offset?: number; length?: number; }): number

Reads data from this stream. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let stream = fs.createStreamSync(filePath, "r+");
class Option {
  offset: number = 0;
  length: number = 0;
}
let option = new Option();
option.offset = 5;
option.length = 5;
let buf = new ArrayBuffer(4096);
let num = stream.readSync(buf, option);
stream.close();

File

Represents a File object opened by open().

System capability: SystemCapability.FileManagement.File.FileIO

Attributes

lock

lock(exclusive?: boolean): Promise<void>

Applies an exclusive lock or a shared lock on this file in blocking mode. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
file.lock(true).then(() => {
  console.log("lock file succeed");
}).catch((err: BusinessError) => {
  console.error("lock file failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  fs.closeSync(file);
});

lock

lock(exclusive?: boolean, callback: AsyncCallback<void>): void

Applies an exclusive lock or a shared lock on this file in blocking mode. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
file.lock(true, (err: BusinessError) => {
  if (err) {
    console.error("lock file failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.log("lock file succeed");
  }
  fs.closeSync(file);
});

tryLock

tryLock(exclusive?: boolean): void

Applies an exclusive lock or a shared lock on this file in non-blocking mode.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
file.tryLock(true);
console.log("lock file succeed");
fs.closeSync(file);

unlock

unlock(): void

Unlocks this file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
file.tryLock(true);
file.unlock();
console.log("unlock file succeed");
fs.closeSync(file);

RandomAccessFile

Provides APIs for randomly reading and writing a stream. Before invoking any API of RandomAccessFile, you need to use createRandomAccess() to create a RandomAccessFile instance synchronously or asynchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Attributes

setFilePointer¹⁰⁺

setFilePointer(): void

Sets the file offset pointer.

System capability: SystemCapability.FileManagement.File.FileIO

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let randomAccessFile = fs.createRandomAccessFileSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
randomAccessFile.setFilePointer(1);
randomAccessFile.close();

close¹⁰⁺

close(): void

Closes this RandomAccessFile instance. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let randomAccessFile = fs.createRandomAccessFileSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
randomAccessFile.close();

write¹⁰⁺

write(buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }): Promise<number>

Writes data to a file. This API uses a promise to return the data.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
let randomAccessFile = fs.createRandomAccessFileSync(file);
let bufferLength: number = 4096;
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let option = new Option();
option.offset = 1;
option.length = 5;
let arrayBuffer = new ArrayBuffer(bufferLength);
randomAccessFile.write(arrayBuffer, option).then((bytesWritten: number) => {
  console.info("randomAccessFile bytesWritten: " + bytesWritten);
}).catch((err: BusinessError) => {
  console.error("create randomAccessFile failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  randomAccessFile.close();
  fs.closeSync(file);
});

write¹⁰⁺

write(buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }, callback: AsyncCallback<number>): void

Writes data to a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
let randomAccessFile = fs.createRandomAccessFileSync(file);
let bufferLength: number = 4096;
class Option {
  offset: number = 0;
  length: number = bufferLength;
  encoding: string = 'utf-8';
}
let option = new Option();
option.offset = 1;
let arrayBuffer = new ArrayBuffer(bufferLength);
randomAccessFile.write(arrayBuffer, option, (err: BusinessError, bytesWritten: number) => {
  if (err) {
    console.error("write failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    if (bytesWritten) {
      console.info("write succeed and size is:" + bytesWritten);
    }
  }
  randomAccessFile.close();
  fs.closeSync(file);
});

writeSync¹⁰⁺

writeSync(buffer: ArrayBuffer | string, options?: { offset?: number; length?: number; encoding?: string; }): number

Writes data to a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let randomAccessFile = fs.createRandomAccessFileSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
class Option {
  offset: number = 0;
  length: number = 0;
  encoding: string = 'utf-8';
}
let option = new Option();
option.offset = 5;
option.length = 5;
let bytesWritten = randomAccessFile.writeSync("hello, world", option);
randomAccessFile.close();

read¹⁰⁺

read(buffer: ArrayBuffer, options?: { offset?: number; length?: number; }): Promise<number>

Reads data from a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
let randomAccessFile = fs.createRandomAccessFileSync(file);
let bufferLength: number = 4096;
class Option {
  offset: number = 0;
  length: number = bufferLength;
}
let option = new Option();
option.offset = 1;
option.length = 5;
let arrayBuffer = new ArrayBuffer(bufferLength);
randomAccessFile.read(arrayBuffer, option).then((readLength: number) => {
  console.info("randomAccessFile readLength: " + readLength);
}).catch((err: BusinessError) => {
  console.error("create randomAccessFile failed with error message: " + err.message + ", error code: " + err.code);
}).finally(() => {
  randomAccessFile.close();
  fs.closeSync(file);
});

read¹⁰⁺

read(buffer: ArrayBuffer, options?: { position?: number; offset?: number; length?: number; }, callback: AsyncCallback<number>): void

Reads data from a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

import { BusinessError } from '@ohos.base';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
let randomAccessFile = fs.createRandomAccessFileSync(file);
let length: number = 20;
class Option {
  offset: number = 0;
  length: number = length;
}
let option = new Option();
option.offset = 1;
option.length = 5;
let arrayBuffer = new ArrayBuffer(length);
randomAccessFile.read(arrayBuffer, option, (err: BusinessError, readLength: number) => {
  if (err) {
    console.error("read failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    if (readLength) {
      console.info("read succeed and size is:" + readLength);
    }
  }
  randomAccessFile.close();
  fs.closeSync(file);
});

readSync¹⁰⁺

readSync(buffer: ArrayBuffer, options?: { offset?: number; length?: number; }): number

Reads data from a file. This API returns the result synchronously.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Return value

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
let randomAccessFile = fs.createRandomAccessFileSync(file);
let length: number = 4096;
let arrayBuffer = new ArrayBuffer(length);
let readLength = randomAccessFile.readSync(arrayBuffer);
randomAccessFile.close();
fs.closeSync(file);

Watcher¹⁰⁺

Provides APIs for observing the changes of files or folders. Before using the APIs of Watcher , call createWatcher() to create a Watcher object.

start¹⁰⁺

start(): void

Starts listening.

System capability: SystemCapability.FileManagement.File.FileIO

Error codes

For details about the error codes, see Basic File IO Error Codes.

Example

let filePath = pathDir + "/test.txt";
let watcher = fs.createWatcher(filePath, 0xfff, () => {});
watcher.start();
watcher.stop();