File Management

The fileio module provides APIs for file storage and management, including basic file management, directory management, file information statistics, and stream read and write.

NOTE
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.

Modules to Import

import fileio from '@ohos.fileio';

Guidelines

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

Stage Model

import Ability from '@ohos.application.Ability';
class MainAbility extends Ability {
   onWindowStageCreate(windowStage) {
       let context = this.context;
       let path = context.filesDir;
   }
}

For details about how to obtain the stage model context, see Stage Model.

FA Model

import featureAbility from '@ohos.ability.featureAbility';
let context = featureAbility.getContext();
context.getFilesDir().then((data) => {
     let path = data;
})

For details about how to obtain the context of the FA model, see FA Model.

fileio.stat

stat(path: string): Promise<Stat>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.

Return value

Type	Description
Promise<Stat>	Promise used to return the file information obtained.

Example

fileio.stat(path).then(function(stat){
    console.info("Got file info:"+ JSON.stringify(stat));
}).catch(function(err){
    console.info("Failed to get file info. Error:"+ err);
});

fileio.stat

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
callback	AsyncCallback<Stat>	Yes	Callback invoked to return the file information obtained.

Example

fileio.stat(path, function (err, stat) {
    // Example code in Stat
});

fileio.statSync

statSync(path:string): Stat

Synchronously obtains file information.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.

Return value

Type	Description
Stat	File information obtained.

Example

let stat = fileio.statSync(path);
// Example code in Stat

fileio.opendir

opendir(path: string): Promise<Dir>

Opens a file directory. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory to open.

Return value

Type	Description
Promise<Dir>	Promise used to return the Dir object.

Example

fileio.opendir(path).then(function(dir){
    console.info("Directory opened:"+ JSON.stringify(dir));
}).catch(function(err){
    console.info("Failed to open the directory. Error:"+ err);
});

fileio.opendir

opendir(path: string, callback: AsyncCallback<Dir>): void

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory to open.
callback	AsyncCallback<Dir>	Yes	Callback invoked when the directory is open asynchronously.

Example

fileio.opendir(path, function (err, dir) { 
    // Example code in Dir struct
    // Use read/readSync/close.
});

fileio.opendirSync

opendirSync(path: string): Dir

Synchronously opens a directory.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory to open.

Return value

Type	Description
Dir	A Dir instance corresponding to the directory.

Example

let dir = fileio.opendirSync(path);
// Example code in Dir struct
// Use read/readSync/close.

fileio.access

access(path: string, mode?: number): Promise<void>

Checks whether the current process can access a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	number	No	Options for accessing the file. You can specify multiple options, separated with a bitwise OR operator (\|). The default value is 0. The options are as follows: - 0: check whether the file exists. - 1: check whether the current process has the execute permission on the file. - 2: check whether the current process has the write permission on the file. - 4: check whether the current process has the read permission on the file.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

fileio.access(path).then(function() {
    console.info("Access successful");
}).catch(function(err){
    console.info("Access failed. Error:"+ err);
});

fileio.access

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

Checks whether the current process can access a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	number	No	Options for accessing the file. You can specify multiple options, separated with a bitwise OR operator (\|). The default value is 0. The options are as follows: - 0: check whether the file exists. - 1: check whether the current process has the execute permission on the file. - 2: check whether the current process has the write permission on the file. - 4: check whether the current process has the read permission on the file.
callback	AsyncCallback<void>	Yes	Callback invoked when the file is asynchronously checked.

Example

fileio.access(path, function (err) {
    // Do something.
});

fileio.accessSync

accessSync(path: string, mode?: number): void

Synchronously checks whether the current process can access the specified file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	number	No	Options for accessing the file. You can specify multiple options, separated with a bitwise OR operator (\|). The default value is 0. The options are as follows: - 0: check whether the file exists. - 1: check whether the current process has the execute permission on the file. - 2: check whether the current process has the write permission on the file. - 4: check whether the current process has the read permission on the file.

Example

try {
    fileio.accessSync(path);
} catch(err) {
    console.info("accessSync failed. Error:"+ err);
}

fileio.close⁷⁺

close(fd: number):Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to close.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let fd = fileio.openSync(path);
fileio.close(fd).then(function(){
    console.info("File closed");
}).catch(function(err){
    console.info("Failed to close the file. Error:"+ err);
});

fileio.close⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to close.
callback	AsyncCallback<void>	Yes	Callback invoked when the file is closed asynchronously.

Example

let fd = fileio.openSync(path);
fileio.close(fd, function (err) {
    // Do something.
});

fileio.closeSync

closeSync(fd: number): void

Synchronously closes a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to close.

Example

let fd = fileio.openSync(path);
fileio.closeSync(fd);

fileio.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

Name	Type	Mandatory	Description
src	string \| number	Yes	Path or file descriptor of the file to copy.
dest	string \| number	Yes	Path or file descriptor of the new file.
mode	number	No	Option for overwriting the file of the same name in the destination path. The default value is 0, which is the only value supported. 0: Completely overwrite the file with the same name and truncate the part that is not overwritten.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let src = path;
let dest = src + 'tgt';
fileio.copyFile(src, dest).then(function(){
    console.info("File copied");
}).catch(function(err){
    console.info("Failed to copy the file. Error:"+ err);
});

fileio.copyFile

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
src	string \| number	Yes	Path or file descriptor of the file to copy.
dest	string \| number	Yes	Path or file descriptor of the new file.
mode	number	No	Option for overwriting the file of the same name in the destination path. The default value is 0, which is the only value supported. 0: Completely overwrite the file with the same name and truncate the part that is not overwritten.
callback	AsyncCallback<void>	Yes	Callback invoked when the file is copied asynchronously.

Example

let src = path;
let dest = src + 'tgt';
fileio.copyFile(src, dest, function (err) {
    // Do something.
});

fileio.copyFileSync

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

Synchronously copies a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
src	string \| number	Yes	Path or file descriptor of the file to copy.
dest	string \| number	Yes	Path or file descriptor of the new file.
mode	number	No	Option for overwriting the file of the same name in the destination path. The default value is 0, which is the only value supported. 0: Completely overwrite the file with the same name and truncate the part that is not overwritten.

Example

let src = path;
let dest = src + 'tgt';
fileio.copyFileSync(src, dest);

fileio.mkdir

mkdir(path:string, mode?: number): Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory.
mode	number	No	Permission on the directory to create. You can specify multiple permissions, separated using a bitwise OR operator (\|). The default value is 0o775. - 0o775: The owner has the read, write, and execute permissions, and other users have the read and execute permissions. - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

fileio.mkdir(path).then(function() {
    console.info("Directory created");
}).catch(function (error){
    console.info("Failed to create the directory. Error:"+ error);
});

fileio.mkdir

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory.
mode	number	No	Permission on the directory to create. You can specify multiple permissions, separated using a bitwise OR operator (\|). The default value is 0o775. - 0o775: The owner has the read, write, and execute permissions, and other users have the read and execute permissions. - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.
callback	AsyncCallback<void>	Yes	Callback invoked when the directory is created asynchronously.

Example

fileio.mkdir(path, function(err) {
  console.info("Directory created");
});

fileio.mkdirSync

mkdirSync(path: string, mode?: number): void

Synchronously creates a directory.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory.
mode	number	No	Permission on the directory to create. You can specify multiple permissions, separated using a bitwise OR operator (\|). The default value is 0o775. - 0o775: The owner has the read, write, and execute permissions, and other users have the read and execute permissions. - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Example

fileio.mkdirSync(path);

fileio.open⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
flags	number	No	Option for opening the file. You must specify one of the following options. By default, the file is open in read-only mode. - 0o0: Open the file in read-only mode. - 0o1: Open the file in write-only mode. - 0o2: Open the file in read/write mode. In addition, you can specify the following options, separated using a bitwise OR operator (\|). By default, no additional option is specified. - 0o100: If the file does not exist, create it. If you use this option, you must also specify mode. - 0o200: If 0o100 is added and the file already exists, throw an exception. - 0o1000: If the file exists and is open in write-only or read/write mode, truncate the file length to 0. - 0o2000: Open the file in append mode. New data will be appended to the file (added to the end of the file). - 0o4000: If path points to a named pipe (also known as a FIFO), block special file, or character special file, perform non-blocking operations on the open file and in subsequent I/Os. - 0o200000: If path does not point to a directory, throw an exception. - 0o400000: If path points to a symbolic link, throw an exception. - 0o4010000: Open the file in synchronous I/O mode.
mode	number	No	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). The default value is 0o666. - 0o666: The owner, user group, and other users have the read and write permissions on the file. - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Return value

Type	Description
Promise<number>	Promise used to return the file descriptor of the file opened.

Example

fileio.open(path, 0o1, 0o0200).then(function(number){
    console.info("File opened");
}).catch(function(err){
    console.info("Failed to open the file. Error:"+ err);
});

fileio.open⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
flags	number	Yes	Option for opening the file. You must specify one of the following options. By default, the file is open in read-only mode. - 0o0: Open the file in read-only mode. - 0o1: Open the file in write-only mode. - 0o2: Open the file in read/write mode. In addition, you can specify the following options, separated using a bitwise OR operator (\|). By default, no additional option is specified. - 0o100: If the file does not exist, create it. If you use this option, you must also specify mode. - 0o200: If 0o100 is added and the file already exists, throw an exception. - 0o1000: If the file exists and is open in write-only or read/write mode, truncate the file length to 0. - 0o2000: Open the file in append mode. New data will be appended to the file (added to the end of the file). - 0o4000: If path points to a named pipe (also known as a FIFO), block special file, or character special file, perform non-blocking operations on the open file and in subsequent I/Os. - 0o200000: If path does not point to a directory, throw an exception. - 0o400000: If path points to a symbolic link, throw an exception. - 0o4010000: Open the file in synchronous I/O mode.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). The default value is 0o666. - 0o666: The owner, user group, and other users have the read and write permissions on the file. - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.
callback	AsyncCallback <void>	Yes	Callback invoked when the file is open asynchronously.

Example

fileio.open(path, 0, function(err, fd) {
    // Do something.
});

fileio.openSync

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

Synchronously opens a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
flags	number	No	Option for opening the file. You must specify one of the following options. By default, the file is open in read-only mode. - 0o0: Open the file in read-only mode. - 0o1: Open the file in write-only mode. - 0o2: Open the file in read/write mode. In addition, you can specify the following options, separated using a bitwise OR operator (\|). By default, no additional option is specified. - 0o100: If the file does not exist, create it. If you use this option, you must also specify mode. - 0o200: If 0o100 is added and the file already exists, throw an exception. - 0o1000: If the file exists and is open in write-only or read/write mode, truncate the file length to 0. - 0o2000: Open the file in append mode. New data will be appended to the file (added to the end of the file). - 0o4000: If path points to a named pipe (also known as a FIFO), block special file, or character special file, perform non-blocking operations on the open file and in subsequent I/Os. - 0o200000: If path does not point to a directory, throw an exception. - 0o400000: If path points to a symbolic link, throw an exception. - 0o4010000: Open the file in synchronous I/O mode.
mode	number	No	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). The default value is 0o666. - 0o666: The owner, user group, and other users have the read and write permissions on the file. - 0o640: The owner has the read and write permissions, and the user group has the read permission. - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission. The file permissions on newly created files are affected by umask, which is set as the process starts. Currently, the modification of umask is not open.

Return value

Type	Description
number	File descriptor of the file opened.

Example

let fd = fileio.openSync(path, 0o102, 0o640);

let fd = fileio.openSync(path, 0o102, 0o666);
fileio.writeSync(fd, 'hello world');
let fd1 = fileio.openSync(path, 0o2002);
fileio.writeSync(fd1, 'hello world');
let num = fileio.readSync(fd1, new ArrayBuffer(4096), {position: 0});
console.info("num == " + num);

fileio.read

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to read.
buffer	ArrayBuffer	Yes	Buffer used to store the file data read.
options	Object	No	The options are as follows: - offset (number): position to store the data read in the buffer in reference to the start address of the buffer. The default value is 0. - length (number): length of the data to read. The default value is the buffer length minus the offset. - position (number): position of the data to read in the file. By default, data is read from the current position. Constraints: offset + length <= Buffer size

Return value

Type	Description
Promise<ReadOut>	Promise used to return the data read.

Example

let fd = fileio.openSync(path, 0o2);
let buf = new ArrayBuffer(4096);
fileio.read(fd, buf).then(function(readOut){
    console.info("Read file data successfully");
    console.log(String.fromCharCode.apply(null, new Uint8Array(readOut.buffer)));
}).catch(function(err){
    console.info("Failed to read file data. Error:"+ err);
});

fileio.read

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to read.
buffer	ArrayBuffer	Yes	Buffer used to store the file data read.
options	Object	No	The options are as follows: - offset (number): position to store the data read in the buffer in reference to the start address of the buffer. The default value is 0. - length (number): length of the data to read. The default value is the buffer length minus the offset. - position (number): position of the data to read in the file. By default, data is read from the current position. Constraints: offset + length <= Buffer size
callback	AsyncCallback<ReadOut>	Yes	Callback invoked when the data is read asynchronously.

Example

let fd = fileio.openSync(path, 0o2);
let buf = new ArrayBuffer(4096);
fileio.read(fd, buf, function (err, readOut) {
    if (readOut) {
        console.info("Read file data successfully");
        console.log(String.fromCharCode.apply(null, new Uint8Array(readOut.buffer)));
    }
});

fileio.readSync

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

Synchronously reads data from a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to read.
buffer	ArrayBuffer	Yes	Buffer used to store the file data read.
options	Object	No	The options are as follows: - offset (number): position to store the data read in the buffer in reference to the start address of the buffer. The default value is 0. - length (number): length of the data to read. The default value is the buffer length minus the offset. - position (number): position of the data to read in the file. By default, data is read from the current position. Constraints: offset + length <= Buffer size

Return value

Type	Description
number	Length of the data read.

Example

let fd = fileio.openSync(path, 0o2);
let buf = new ArrayBuffer(4096);
let num = fileio.readSync(fd, buf);

fileio.rmdir⁷⁺

rmdir(path: string): Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

fileio.rmdir(path).then(function() {
    console.info("Directory deleted");
}).catch(function(err){
    console.info("Failed to delete the directory. Error:"+ err);
});

fileio.rmdir⁷⁺

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

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory.
callback	AsyncCallback<void>	Yes	Callback invoked when the directory is deleted asynchronously.

Example

fileio.rmdir(path, function(err){
    // Do something.
    console.info("Directory deleted");
});

fileio.rmdirSync⁷⁺

rmdirSync(path: string): void

Synchronously deletes a directory.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the directory.

Example

fileio.rmdirSync(path);

fileio.unlink

unlink(path:string): Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

fileio.unlink(path).then(function(){
    console.info("File deleted");
}).catch(function(error){
    console.info("Failed to delete the file. Error:"+ error);
});

fileio.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

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
callback	AsyncCallback<void>	Yes	Callback invoked when the file is deleted asynchronously.

Example

fileio.unlink(path, function(err) {
    console.info("File deleted");
});

fileio.unlinkSync

unlinkSync(path: string): void

Synchronously deletes a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.

Example

fileio.unlinkSync(path);

fileio.write

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to write.
buffer	ArrayBuffer \| string	Yes	Data to write. It can be a string or data from a buffer.
options	Object	No	The options are as follows: - offset (number): position of the data to write in reference to the start address of the data. The default value is 0. - length (number): length of the data to write. The default value is the buffer length minus the offset. - position (number): start position to write the data in the file. By default, data is written from the current position. - encoding (string): format of the string to be encoded. The default value is utf-8, which is the only value supported. Constraints: offset + length <= Buffer size

Return value

Type	Description
Promise<number>	Promise used to return the length of the data written.

Example

let fd = fileio.openSync(path, 0o100 | 0o2, 0o666);
fileio.write(fd, "hello, world").then(function(number){
     console.info("Data written to the file. Size is:"+ number);
}).catch(function(err){
    console.info("Failed to write data to the file. Error:"+ err);
});

fileio.write

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to write.
buffer	ArrayBuffer \| string	Yes	Data to write. It can be a string or data from a buffer.
options	Object	No	The options are as follows: - offset (number): position of the data to write in reference to the start address of the data. The default value is 0. - length (number): length of the data to write. The default value is the buffer length minus the offset. - position (number): start position to write the data in the file. By default, data is written from the current position. - encoding (string): format of the string to be encoded. The default value is utf-8, which is the only value supported. Constraints: offset + length <= Buffer size
callback	AsyncCallback<number>	Yes	Callback invoked when the data is written asynchronously.

Example

let fd = fileio.openSync(path, 0o100 | 0o2, 0o666);
fileio.write(fd, "hello, world", function (err, bytesWritten) {
    if (bytesWritten) {
       console.info("Data written to the file. Size is:"+ bytesWritten);
    }
});

fileio.writeSync

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

Synchronously writes data into a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to write.
buffer	ArrayBuffer \| string	Yes	Data to write. It can be a string or data from a buffer.
options	Object	No	The options are as follows: - offset (number): position of the data to write in reference to the start address of the data. The default value is 0. - length (number): length of the data to write. The default value is the buffer length minus the offset. - position (number): start position to write the data in the file. By default, data is written from the current position. - encoding (string): format of the string to be encoded. The default value is utf-8, which is the only value supported. Constraints: offset + length <= Buffer size

Return value

Type	Description
number	Length of the data written in the file.

Example

let fd = fileio.openSync(path, 0o100 | 0o2, 0o666);
let num = fileio.writeSync(fd, "hello, world");

fileio.hash

hash(path: string, algorithm: string): Promise<string>

Calculates the hash value of a file. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
algorithm	string	Yes	Algorithm used to calculate the hash value. The value can be md5, sha1, or sha256. sha256 is recommended for security purposes.

Return value

Type	Description
Promise<string>	Promise used to return the hash value obtained. The hash value is a hexadecimal string consisting of digits and uppercase letters.

Example

fileio.hash(path, "sha256").then(function(str){
    console.info("Calculated file hash:"+ str);
}).catch(function(err){
    console.info("Failed to calculate the file hash. Error:"+ err);
});

fileio.hash

hash(path: string, algorithm: string, callback: AsyncCallback<string>): void

Calculates the hash value of a file. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
algorithm	string	Yes	Algorithm used to calculate the hash value. The value can be md5, sha1, or sha256. sha256 is recommended for security purposes.
callback	AsyncCallback<string>	Yes	Callback used to return the hash value obtained. The hash value is a hexadecimal string consisting of digits and uppercase letters.

Example

fileio.hash(path, "sha256", function(err, hashStr) {
    if (hashStr) {
        console.info("Calculated file hash:"+ hashStr);
    }
});

fileio.chmod⁷⁺

chmod(path: string, mode: number):Promise<void>

Changes file permissions. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

fileio.chmod(path, 0o700).then(function() {
    console.info("File permissions changed");
}).catch(function(err){
    console.info("Failed to change file permissions. Error:"+ err);
});

fileio.chmod⁷⁺

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

Changes file permissions. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.
callback	AsyncCallback<void>	Yes	Callback invoked when the file permissions are changed asynchronously.

Example

fileio.chmod(path, 0o700, function (err) {
    // Do something.
});

fileio.chmodSync⁷⁺

chmodSync(path: string, mode: number): void

Synchronously changes file permissions.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Example

fileio.chmodSync(path, 0o700);

fileio.fstat⁷⁺

fstat(fd: number): Promise<Stat>

Obtains file information based on the file descriptor. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.

Return value

Type	Description
Promise<Stat>	Promise used to return the file information.

Example

let fd = fileio.openSync(path);
fileio.fstat(fd).then(function(stat){
    console.info("Obtained file info:"+ JSON.stringify(stat));
}).catch(function(err){
    console.info("Failed to obtain file info. Error:"+ err);
});

fileio.fstat⁷⁺

fstat(fd: number, callback: AsyncCallback<Stat>): void

Obtains file information based on the file descriptor. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
callback	AsyncCallback<Stat>	Yes	Callback invoked to return the file information obtained.

Example

let fd = fileio.openSync(path);
fileio.fstat(fd, function (err) {
    // Do something.
});

fileio.fstatSync⁷⁺

fstatSync(fd: number): Stat

Synchronously obtains file information based on the file descriptor.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.

Return value

Type	Description
Stat	File information obtained.

Example

let fd = fileio.openSync(path);
let stat = fileio.fstatSync(fd);

fileio.ftruncate⁷⁺

ftruncate(fd: number, len?: number): Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to truncate.
len	number	No	File length, in bytes, after truncation.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let fd = fileio.openSync(path);
fileio.ftruncate(fd, 5).then(function(err) {    
    console.info("File truncated");
}).catch(function(err){
    console.info("Failed to truncate the file. Error:"+ err);
});

fileio.ftruncate⁷⁺

ftruncate(fd: number, len: number, callback:AsyncCallback<void>): void

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to truncate.
len	number	Yes	File length, in bytes, after truncation.
callback	AsyncCallback<void>	Yes	Callback that returns no value.

Example

let fd = fileio.openSync(path);
let len = 5;
fileio.ftruncate(fd, 5, function(err){
    // Do something.
});

fileio.ftruncateSync⁷⁺

ftruncateSync(fd: number, len?: number): void

Synchronously truncates a file based on the file descriptor.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to truncate.
len	number	No	File length, in bytes, after truncation.

Example

let fd = fileio.openSync(path);
let len = 5;
fileio.ftruncateSync(fd, len);

fileio.truncate⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file to truncate.
len	number	No	File length, in bytes, after truncation.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let len = 5;
fileio.truncate(path, len).then(function(){
    console.info("File truncated");
}).catch(function(err){
    console.info("Failed to truncate the file. Error:"+ err);
});

fileio.truncate⁷⁺

truncate(path: string, len: number, callback:AsyncCallback<void>): void

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file to truncate.
len	number	Yes	File length, in bytes, after truncation.
callback	AsyncCallback<void>	Yes	Callback that returns no value.

Example

let len = 5;
fileio.truncate(path, len, function(err){
    // Do something.
});

fileio.truncateSync⁷⁺

truncateSync(path: string, len?: number): void

Synchronously truncates a file based on the file path.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file to truncate.
len	number	No	File length, in bytes, after truncation.

Example

let len = 5;
fileio.truncateSync(path, len);

fileio.readText⁷⁺

readText(filePath: string, options?: { position?: 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

Name	Type	Mandatory	Description
filePath	string	Yes	Application sandbox path of the file to read.
options	Object	No	The options are as follows: - position (number): position of the data to read in the file. By default, data is read from the current position. - length (number): length of the data to read. The default value is the buffer length minus the offset. - encoding (string): format of the data (string) to be encoded. The default value is utf-8, which is the only value supported.

Return value

Type	Description
Promise<string>	Promise used to return the content read.

Example

fileio.readText(path).then(function(str) {
    console.info("Read text successfully:"+ str);
}).catch(function(err){
    console.info("Failed to read the text. Error:"+ err);
});

fileio.readText⁷⁺

readText(filePath: string, options: { position?: 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

Name	Type	Mandatory	Description
filePath	string	Yes	Application sandbox path of the file to read.
options	Object	Yes	The options are as follows: - position (number): position of the data to read in the file. By default, data is read from the current position. - length (number): length of the data to read. The default value is the buffer length minus the offset. - encoding: format of the string to be encoded. The default value is utf-8, which is the only value supported.
callback	AsyncCallback<string>	Yes	Callback used to return the content read.

Example

fileio.readText(path, { position: 1, encoding: 'UTF-8' }, function(err, str){
    // Do something.
});

fileio.readTextSync⁷⁺

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

Synchronously reads the text of a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
filePath	string	Yes	Application sandbox path of the file to read.
options	Object	No	The options are as follows: - position (number): position of the data to read in the file. By default, data is read from the current position. - length (number): length of the data to read. The default value is the buffer length minus the offset. - encoding (string): format of the data (string) to be encoded. The default value is utf-8, which is the only value supported.

Return value

Type	Description
string	Promise used to return the content of the file read.

Example

let str = fileio.readTextSync(path, {position: 1, length: 3});

fileio.lstat⁷⁺

lstat(path: string): Promise<Stat>

Obtains link information. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the target file.

Return value

Type	Description
Promise<Stat>	Promise used to return the link information obtained. For details, see Stat.

Example

fileio.lstat(path).then(function(stat){
    console.info("Got link info:"+ JSON.stringify(stat));
}).catch(function(err){
    console.info("Failed to obtain link info. Error:"+ err);
});

fileio.lstat⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the target file.
callback	AsyncCallback<Stat>	Yes	Callback used to return the link information obtained.

Example

fileio.lstat(path, function (err, stat) {
    // Do something.
});

fileio.lstatSync⁷⁺

lstatSync(path:string): Stat

Synchronously obtains the link information.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the target file.

Return value

Type	Description
Stat	Link information obtained.

Example

let stat = fileio.lstatSync(path);

fileio.rename⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
oldPath	string	Yes	Application sandbox path of the file to rename.
newPath	String	Yes	Application sandbox path of the file renamed.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let oldPath = path;
let newPath = oldPath + '123';
fileio.rename(oldPath, newPath).then(function() {
    console.info("File renamed");
}).catch(function(err){
    console.info("Failed to rename the file. Error:"+ err);
});

fileio.rename⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
oldPath	string	Yes	Application sandbox path of the file to rename.
newPath	String	Yes	Application sandbox path of the file renamed.
Callback	AsyncCallback<void>	Yes	Callback invoked when the file is asynchronously renamed.

Example

let oldPath = path;
let newPath = oldPath + '123';
fileio.rename(oldPath, newPath, function(err){
});

fileio.renameSync⁷⁺

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

Synchronously renames a file.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
oldPath	string	Yes	Application sandbox path of the file to rename.
newPath	String	Yes	Application sandbox path of the file renamed.

Example

let oldPath = path;
let newPath = oldPath + '123';
fileio.renameSync(oldPath, newPath);

fileio.fsync⁷⁺

fsync(fd: number): Promise<void>

Flushes data of a file to disk. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to flush.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let fd = fileio.openSync(path);
fileio.fsync(fd).then(function(){
    console.info("Data flushed");
}).catch(function(err){
    console.info("Failed to flush data. Error:"+ err);
});

fileio.fsync⁷⁺

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

Flushes data of a file to disk. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to flush.
Callback	AsyncCallback<void>	Yes	Callback invoked when the file is synchronized in asynchronous mode.

Example

let fd = fileio.openSync(path);
fileio.fsync(fd, function(err){
    // Do something.
});

fileio.fsyncSync⁷⁺

fsyncSync(fd: number): void

Flushes data of a file to disk in synchronous mode.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to flush.

Example

let fd = fileio.openSync(path);
fileio.fsyncSync(fd);

fileio.fdatasync⁷⁺

fdatasync(fd: number): Promise<void>

Flushes data of a file to disk. 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

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to flush.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let fd = fileio.openSync(path);
fileio.fdatasync(fd).then(function(err) {
    console.info("Data flushed");
}).catch(function(err){
    console.info("Failed to flush data. Error:"+ err);
});

fileio.fdatasync⁷⁺

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

Flushes data of a file to disk. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to synchronize.
callback	AsyncCallback <void>	Yes	Callback invoked when the file data is synchronized in asynchronous mode.

Example

let fd = fileio.openSync(path);
fileio.fdatasync (fd, function (err) {
    // Do something.
});

fileio.fdatasyncSync⁷⁺

fdatasyncSync(fd: number): void

Synchronizes data in a file in synchronous mode.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the file to flush.

Example

let fd = fileio.openSync(path);
let stat = fileio.fdatasyncSync(fd);

fileio.symlink⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
target	string	Yes	Application sandbox path of the target file.
srcPath	string	Yes	Application sandbox path of the symbolic link file.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let target = path;
let srcPath = target + 'aaa';
fileio.symlink(target, srcPath).then(function() {
    console.info("Symbolic link created");
}).catch(function(err){
    console.info("Failed to create the symbolic link. Error:"+ err);
});

fileio.symlink⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
target	string	Yes	Application sandbox path of the target file.
srcPath	string	Yes	Application sandbox path of the symbolic link file.
callback	AsyncCallback<void>	Yes	Callback invoked when the symbolic link is created asynchronously.

Example

let target = path;
let srcPath = target + 'aaa';
fileio.symlink(target, srcPath, function (err) {
    // Do something.
});

fileio.symlinkSync⁷⁺

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

Synchronously creates a symbolic link based on a specified path.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
target	string	Yes	Application sandbox path of the target file.
srcPath	string	Yes	Application sandbox path of the symbolic link file.

Example

let target = path;
let srcPath = target + 'aaa';
fileio.symlinkSync(target, srcPath);

fileio.chown⁷⁺

chown(path: string, uid: number, gid: number): Promise<void>

Changes the file owner based on the file path. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
uid	number	Yes	New user ID (UID).
gid	number	Yes	New group ID (GID).

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let stat = fileio.statSync(path);
fileio.chown(path, stat.uid, stat.gid).then(function(){
    console.info("File owner changed");
}).catch(function(err){
    console.info("Failed to change the file owner. Error:"+ err);
});

fileio.chown⁷⁺

chown(path: string, uid: number, gid: number, callback: AsyncCallback<void>): void

Changes the file owner based on the file path. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.
callback	AsyncCallback<void>	Yes	Callback invoked when the file owner is changed asynchronously.

Example

let stat = fileio.statSync(path)
fileio.chown(path, stat.uid, stat.gid, function (err){
    // Do something.
});

fileio.chownSync⁷⁺

chownSync(path: string, uid: number, gid: number): void

Synchronously changes the file owner based on its path.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.

Example

let stat = fileio.statSync(path)
fileio.chownSync(path, stat.uid, stat.gid);

fileio.mkdtemp⁷⁺

mkdtemp(prefix: string): Promise<string>

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
prefix	string	Yes	A randomly generated string used to replace "XXXXXX" in a directory.

Return value

Type	Description
Promise<string>	Promise used to return the unique directory generated.

Example

fileio.mkdtemp(path + "XXXX").then(function(path){
    console.info("Temporary directory created:"+ path);
}).catch(function(err){
    console.info("Failed to create the temporary directory. Error:"+ err);
});

fileio.mkdtemp⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
prefix	string	Yes	A randomly generated string used to replace "XXXXXX" in a directory.
callback	AsyncCallback<string>	Yes	Callback invoked when a temporary directory is created asynchronously.

Example

fileio.mkdtemp(path + "XXXX", function (err, res) {
    // Do something.
});

fileio.mkdtempSync⁷⁺

mkdtempSync(prefix: string): string

Synchronously creates a temporary directory.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
prefix	string	Yes	A randomly generated string used to replace "XXXXXX" in a directory.

Return value

Type	Description
string	Unique path generated.

Example

let res = fileio.mkdtempSync(path + "XXXX");

fileio.fchmod⁷⁺

fchmod(fd: number, mode: number): Promise<void>

Changes file permissions based on the file descriptor. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let fd = fileio.openSync(path);
let mode = 0o700;
fileio.fchmod(fd, mode).then(function() {
    console.info("File permissions changed");
}).catch(function(err){
    console.info("Failed to change file permissions. Error:"+ err);
});

fileio.fchmod⁷⁺

fchmod(fd: number, mode: number, callback: AsyncCallback<void>): void

Changes file permissions based on the file descriptor. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.
callback	AsyncCallback <void>	Yes	Callback invoked when the file permissions are changed asynchronously.

Example

let fd = fileio.openSync(path);
let mode = 0o700;
fileio.fchmod(fd, mode, function (err) {
    // Do something.
});

fileio.fchmodSync⁷⁺

fchmodSync(fd: number, mode: number): void

Synchronously changes the file permissions based on the file descriptor.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
mode	number	Yes	Permissions on the file. You can specify multiple permissions, separated using a bitwise OR operator (\|). - 0o700: The owner has the read, write, and execute permissions. - 0o400: The owner has the read permission. - 0o200: The owner has the write permission. - 0o100: The owner has the execute permission. - 0o070: The user group has the read, write, and execute permissions. - 0o040: The user group has the read permission. - 0o020: The user group has the write permission. - 0o010: The user group has the execute permission. - 0o007: Other users have the read, write, and execute permissions. - 0o004: Other users have the read permission. - 0o002: Other users have the write permission. - 0o001: Other users have the execute permission.

Example

let fd = fileio.openSync(path);
let mode = 0o700;
 fileio.fchmodSync(fd, mode);

fileio.createStream⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	string	Yes	- r: Open a file for reading. The file must exist. - r+: Open a file for both reading and writing. The file must exist. - w: Open a file for writing. If the file exists, clear its content. If the file does not exist, create a file. - w+: Open a file for both reading and writing. If the file exists, clear its content. If the file does not exist, create a file. - a: Open a file in append mode for writing at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved). - a+: Open a file in append mode for reading or updating at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved).

Return value

Type	Description
Promise<Stream>	Promise used to return the result.

Example

fileio.createStream(path, "r+").then(function(stream){
    console.info("Stream opened");
}).catch(function(err){
    console.info("Failed to create the stream. Error:"+ err);
});

fileio.createStream⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	string	Yes	- r: Open a file for reading. The file must exist. - r+: Open a file for both reading and writing. The file must exist. - w: Open a file for writing. If the file exists, clear its content. If the file does not exist, create a file. - w+: Open a file for both reading and writing. If the file exists, clear its content. If the file does not exist, create a file. - a: Open a file in append mode for writing at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved). - a+: Open a file in append mode for reading or updating at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved).
callback	AsyncCallback<Stream>	Yes	Callback invoked when the stream is open asynchronously.

Example

fileio.createStream(path, "r+", function(err, stream){
    // Do something.
});

fileio.createStreamSync⁷⁺

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

Synchronously opens a stream based on the file path.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
mode	string	Yes	- r: Open a file for reading. The file must exist. - r+: Open a file for both reading and writing. The file must exist. - w: Open a file for writing. If the file exists, clear its content. If the file does not exist, create a file. - w+: Open a file for both reading and writing. If the file exists, clear its content. If the file does not exist, create a file. - a: Open a file in append mode for writing at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved). - a+: Open a file in append mode for reading or updating at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved).

Return value

Type	Description
Stream	Stream opened.

Example

let ss = fileio.createStreamSync(path, "r+");

fileio.fdopenStream⁷⁺

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

Opens a file stream based on the file descriptor. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
mode	string	Yes	- r: Open a file for reading. The file must exist. - r+: Open a file for both reading and writing. The file must exist. - w: Open a file for writing. If the file exists, clear its content. If the file does not exist, create a file. - w+: Open a file for both reading and writing. If the file exists, clear its content. If the file does not exist, create a file. - a: Open a file in append mode for writing at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved). - a+: Open a file in append mode for reading or updating at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved).

Return value

Type	Description
Promise<Stream>	Promise used to return the result.

Example

let fd = fileio.openSync(path);
fileio.fdopenStream(fd, "r+").then(function(stream){
    console.info("Stream opened");
}).catch(function(err){
    console.info("Failed to open the stream. Error:"+ err);
});

fileio.fdopenStream⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
mode	string	Yes	- r: Open a file for reading. The file must exist. - r+: Open a file for both reading and writing. The file must exist. - w: Open a file for writing. If the file exists, clear its content. If the file does not exist, create a file. - w+: Open a file for both reading and writing. If the file exists, clear its content. If the file does not exist, create a file. - a: Open a file in append mode for writing at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved). - a+: Open a file in append mode for reading or updating at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved).
callback	AsyncCallback <Stream>	Yes	Callback invoked when the stream is open asynchronously.

Example

let fd = fileio.openSync(path);
fileio.fdopenStream(fd, "r+", function (err, stream) {
    // Do something.
});

fileio.fdopenStreamSync⁷⁺

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

Synchronously opens a stream based on the file descriptor.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
mode	string	Yes	- r: Open a file for reading. The file must exist. - r+: Open a file for both reading and writing. The file must exist. - w: Open a file for writing. If the file exists, clear its content. If the file does not exist, create a file. - w+: Open a file for both reading and writing. If the file exists, clear its content. If the file does not exist, create a file. - a: Open a file in append mode for writing at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved). - a+: Open a file in append mode for reading or updating at the end of the file. If the file does not exist, create a file. If the file exists, write data to the end of the file (the original content of the file is reserved).

Return value

Type	Description
Stream	Stream opened.

Example

let fd = fileio.openSync(path);
let ss = fileio.fdopenStreamSync(fd, "r+");

fileio.fchown⁷⁺

fchown(fd: number, uid: number, gid: number): Promise<void>

Changes the file owner based on the file descriptor. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let fd = fileio.openSync(path);
let stat = fileio.statSync(path);
fileio.fchown(fd, stat.uid, stat.gid).then(function() {
    console.info("File owner changed");
}).catch(function(err){
    console.info("Failed to change the file owner. Error:"+ err);
});

fileio.fchown⁷⁺

fchown(fd: number, uid: number, gid: number, callback: AsyncCallback<void>): void

Changes the file owner based on the file descriptor. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.
callback	AsyncCallback<void>	Yes	Callback invoked when the file owner is changed asynchronously.

Example

let fd = fileio.openSync(path);
let stat = fileio.statSync(path);
fileio.fchown(fd, stat.uid, stat.gid, function (err){
    // Do something.
});

fileio.fchownSync⁷⁺

fchownSync(fd: number, uid: number, gid: number): void

Synchronously changes the file owner based on the file descriptor.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
fd	number	Yes	File descriptor of the target file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.

Example

let fd = fileio.openSync(path);
let stat = fileio.statSync(path);
fileio.fchownSync(fd, stat.uid, stat.gid);

fileio.lchown⁷⁺

lchown(path: string, uid: number, gid: number): Promise<void>

Changes the file owner (owner of the symbolic link, not the file referred to by the symbolic link) based on the file path. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Example

let stat = fileio.statSync(path);
fileio.lchown(path, stat.uid, stat.gid).then(function() {
    console.info("File owner changed");
}).catch(function(err){
    console.info("Failed to change the file owner. Error:"+ err);
});

fileio.lchown⁷⁺

lchown(path: string, uid: number, gid: number, callback: AsyncCallback<void>): void

Changes the file owner (owner of the symbolic link, not the file referred to by the symbolic link) based on the file path. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.
callback	AsyncCallback<void>	Yes	Callback invoked when the file owner is changed asynchronously.

Example

let stat = fileio.statSync(path);
fileio.lchown(path, stat.uid, stat.gid, function (err){
    // Do something.
});

fileio.lchownSync⁷⁺

lchownSync(path: string, uid: number, gid: number): void

Synchronously changes the file owner based on the file path and changes the owner of the symbolic link (not the referenced file).

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
path	string	Yes	Application sandbox path of the file.
uid	number	Yes	New UID.
gid	number	Yes	New GID.

Example

let stat = fileio.statSync(path);
fileio.lchownSync(path, stat.uid, stat.gid);

fileio.createWatcher⁷⁺

createWatcher(filename: string, events: number, callback: AsyncCallback<number>): Watcher

Listens for file or directory changes. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
filename	string	Yes	Application sandbox path of the file.
events	Number	Yes	- 1: The file or directory is renamed. - 2: The file or directory is modified. - 3: The file or directory is modified and renamed.
callback	AsyncCallback<number >	Yes	Called each time a change is detected.

Return value

Type	Description
Watcher	Promise used to return the Watcher instance.

Example

let filename = path +"/test.txt";
fileio.createWatcher(filename, 1, function(number){
   console.info("Monitoring times: "+number);
});

Readout

Obtains the file read result. This class applies only to the read() method.

System capability: SystemCapability.FileManagement.File.FileIO

Name	Type	Readable	Writable	Description
bytesRead	number	Yes	Yes	Length of the data read.
offset	number	Yes	Yes	Position of the buffer to which the data will be read in reference to the start address of the buffer.
buffer	ArrayBufer	Yes	Yes	Buffer for storing the data read.

Stat

Provides detailed file information. Before calling a method of the Stat class, use the stat() method synchronously or asynchronously to create a Stat instance.

System capability: SystemCapability.FileManagement.File.FileIO

Attributes

Name	Type	Readable	Writable	Description
dev	number	Yes	No	Major device number.
ino	number	Yes	No	File ID. Different files on the same device have different inos.
mode	number	Yes	No	File type and permissions. The first four bits indicate the file type, and the last 12 bits indicate the permissions. The bit fields are described as follows: - 0o170000: mask used to obtain the file type. - 0o140000: The file is a socket. - 0o120000: The file is a symbolic link. - 0o100000: The file is a regular file. - 0o060000: The file is a block device. - 0o040000: The file is a directory. - 0o020000: The file is a character device. - 0o010000: The file is a named pipe (FIFO). - 0o0700: mask used to obtain the owner permissions. - 0o0400: The owner has the permission to read a regular file or a directory entry. - 0o0200: The owner has the permission to write a regular file or create and delete a directory entry. - 0o0100: The owner has the permission to execute a regular file or search for the specified path in a directory. - 0o0070: mask used to obtain the user group permissions. - 0o0040: The user group has the permission to read a regular file or a directory entry. - 0o0020: The user group has the permission to write a regular file or create and delete a directory entry. - 0o0010: The user group has the permission to execute a regular file or search for the specified path in a directory. - 0o0007: mask used to obtain the permissions of other users. - 0o0004: Other users have the permission to read a regular file or a directory entry. - 0o0002: Other users have the permission to write a regular file or create and delete a directory entry. - 0o0001: Other users have the permission to execute a regular file or search for the specified path in a directory.
nlink	number	Yes	No	Number of hard links in the file.
uid	number	Yes	No	User ID, that is ID of the file owner.
gid	number	Yes	No	Group ID, that is, ID of the user group of the file.
rdev	number	Yes	No	Minor device number.
size	number	Yes	No	File size, in bytes. This parameter is valid only for regular files.
blocks	number	Yes	No	Number of blocks occupied by a file. Each block is 512 bytes.
atime	number	Yes	No	Time of the last access to the file. The value is the number of seconds elapsed since 00:00:00 on January 1, 1970.
mtime	number	Yes	No	Time of the last modification to the file. The value is the number of seconds elapsed since 00:00:00 on January 1, 1970.
ctime	number	Yes	No	Time of the last status change of the file. The value is the number of seconds elapsed since 00:00:00 on January 1, 1970.

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

Type	Description
boolean	Whether the file is a block special file.

Example

let isBLockDevice = fileio.statSync(path).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

Type	Description
boolean	Whether the file is a character special file.

Example

let isCharacterDevice = fileio.statSync(path).isCharacterDevice();

isDirectory

isDirectory(): boolean

Checks whether this file is a directory.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the file is a directory.

Example

let isDirectory = fileio.statSync(path).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

Type	Description
boolean	Whether the file is an FIFO.

Example

let isFIFO = fileio.statSync(path).isFIFO();

isFile

isFile(): boolean

Checks whether this file is a regular file.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the file is a regular file.

Example

let isFile = fileio.statSync(path).isFile();

isSocket

isSocket(): boolean

Checks whether this file is a socket.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the file is a socket.

Example

let isSocket = fileio.statSync(path).isSocket();

isSymbolicLink

isSymbolicLink(): boolean

Checks whether this file is a symbolic link.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the file is a symbolic link.

Example

let isSymbolicLink = fileio.statSync(path).isSymbolicLink();

Watcher⁷⁺

Listens for the changes of a file. You can call the Watcher.stop() method synchronously or asynchronously to stop the listening.

stop⁷⁺

stop(): Promise<void>

Stops the watcher instance. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Example

let filename = path +"/test.txt";
let watcher = fileio.createWatcher(filename, 1, function(number){
    console.info("Monitoring times: "+number);
});
watcher.stop().then(function(){
     console.info("Watcher stopped");
});

stop⁷⁺

stop(callback: AsyncCallback<void>): void

Stops the watcher instance. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
callback	AsyncCallback<void>	Yes	Callback invoked when watcher is stopped asynchronously.

Example

let filename = path +"/test.txt";
let watcher = fileio.createWatcher(filename, 1, function(number){
    console.info("Monitoring times: "+number);
});
watcher.stop(function(){
    console.info("Watcher stopped");
})

Stream

Provides file stream management. Before calling a method of the Stream class, use the createStream() method synchronously or asynchronously to create a Stream instance.

close⁷⁺

close(): Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Return value

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

Example

let ss= fileio.createStreamSync(path, "r+");
ss.close().then(function(){
    console.info("File stream closed");
}).catch(function(err){
    console.info("Failed to close the file stream. Error:"+ err);
});

close⁷⁺

close(callback: AsyncCallback<void>): void

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
callback	AsyncCallback<void>	Yes	Callback invoked when the stream is closed asynchronously.

Example

let ss= fileio.createStreamSync(path, "r+");
ss.close(function (err) {
    // Do something
});

closeSync

closeSync(): void

Synchronously closes the stream.

System capability: SystemCapability.FileManagement.File.FileIO

Example

let ss= fileio.createStreamSync(path, "r+");
ss.closeSync();

flush⁷⁺

flush(): Promise<void>

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

System capability: SystemCapability.FileManagement.File.FileIO

Return value

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

Example

let ss= fileio.createStreamSync(path, "r+");
ss.flush().then(function (){
    console.info("Stream flushed");
}).catch(function(err){
    console.info("Failed to flush the stream. Error:"+ err);
});

flush⁷⁺

flush(callback: AsyncCallback<void>): void

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
callback	AsyncCallback<void>	Yes	Callback invoked when the stream is asynchronously flushed.

Example

let ss= fileio.createStreamSync(path, "r+");
ss.flush(function (err) {
    // Do something
});

flushSync⁷⁺

flushSync(): void

Synchronously flushes the stream.

System capability: SystemCapability.FileManagement.File.FileIO

Example

let ss= fileio.createStreamSync(path, "r+");
ss.flushSync();

write⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
buffer	ArrayBuffer \| string	Yes	Data to write. It can be a string or data from a buffer.
options	Object	No	The options are as follows: - offset (number): position of the data to write in reference to the start address of the data. The default value is 0. - length (number): length of the data to write. The default value is the buffer length minus the offset. - position (number): start position to write the data in the file. By default, data is written from the current position. - encoding (string): format of the string to be encoded. The default value is utf-8, which is the only value supported. Constraints: offset + length <= Buffer size

Return value

Type	Description
Promise<number>	Promise used to return the length of the data written.

Example

let ss= fileio.createStreamSync(path, "r+");
ss.write("hello, world",{offset: 1,length: 5,position: 5,encoding :'utf-8'}).then(function (number){
    console.info("Data written to the stream. Size is:"+ number);
}).catch(function(err){
    console.info("Failed to write data to the stream. Error:"+ err);
});

write⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
buffer	ArrayBuffer \| string	Yes	Data to write. It can be a string or data from a buffer.
options	Object	No	The options are as follows: - offset (number): position of the data to write in reference to the start address of the data. The default value is 0. - length (number): length of the data to write. The default value is the buffer length minus the offset. - position (number): start position to write the data in the file. By default, data is written from the current position. - encoding (string): format of the string to be encoded. The default value is utf-8, which is the only value supported. Constraints: offset + length <= Buffer size
callback	AsyncCallback<number>	Yes	Callback invoked when the data is written asynchronously.

Example

let ss= fileio.createStreamSync(path, "r+");
ss.write("hello, world", {offset: 1, length: 5, position: 5, encoding :'utf-8'}, function (err, bytesWritten) {
    if (bytesWritten) {
       // Do something
       console.info("Data written to the stream. Size is:"+ bytesWritten);
    }
});

writeSync⁷⁺

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

Synchronously writes data into the stream.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
buffer	ArrayBuffer \| string	Yes	Data to write. It can be a string or data from a buffer.
options	Object	No	The options are as follows: - offset (number): position of the data to write in reference to the start address of the data. The default value is 0. - length (number): length of the data to write. The default value is the buffer length minus the offset. - position (number): start position to write the data in the file. By default, data is written from the current position. - encoding (string): format of the string to be encoded. The default value is utf-8, which is the only value supported. Constraints: offset + length <= Buffer size

Return value

Type	Description
number	Length of the data written in the file.

Example

let ss= fileio.createStreamSync(path,"r+");
let num = ss.writeSync("hello, world", {offset: 1, length: 5, position: 5, encoding :'utf-8'});

read⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
buffer	ArrayBuffer	Yes	Buffer used to store the file read.
options	Object	No	The options are as follows: - offset (number): position to store the data read in the buffer in reference to the start address of the buffer. The default value is 0. - length (number): length of the data to read. The default value is the buffer length minus the offset. - position (number): position of the data to read in the file. By default, data is read from the current position. Constraints: offset + length <= Buffer size

Return value

Type	Description
Promise<ReadOut>	Promise used to return the data read.

Example

let ss = fileio.createStreamSync(path, "r+");
ss.read(new ArrayBuffer(4096), {offset: 1, length: 5, position: 5}).then(function (readOut){
    console.info("Read data successfully");
    console.log(String.fromCharCode.apply(null, new Uint8Array(readOut.buffer)));
}).catch(function(err){
    console.info("Failed to read data. Error:"+ err);
});

read⁷⁺

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

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

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
buffer	ArrayBuffer	Yes	Buffer used to store the file read.
options	Object	No	The options are as follows: - offset (number): position to store the data read in the buffer in reference to the start address of the buffer. The default value is 0. - length (number): length of the data to read. The default value is the buffer length minus the offset. - position (number): position of the data to read in the file. By default, data is read from the current position. Constraints: offset + length <= Buffer size
callback	AsyncCallback<ReadOut>	Yes	Callback invoked when data is read asynchronously from the stream.

Example

let ss = fileio.createStreamSync(path, "r+");
ss.read(new ArrayBuffer(4096),{offset: 1, length: 5, position: 5},function (err, readOut) {
    if (readOut) {
        console.info("Read data successfully");
        console.log(String.fromCharCode.apply(null, new Uint8Array(readOut.buffer)));
    }
});

readSync⁷⁺

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

Synchronously reads data from the stream.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
buffer	ArrayBuffer	Yes	Buffer used to store the file read.
options	Object	No	The options are as follows: - offset (number): position to store the data read in the buffer in reference to the start address of the buffer. The default value is 0. - length (number): length of the data to read. The default value is the buffer length minus the offset. - position (number): position of the data to read in the file. By default, data is read from the current position. Constraints: offset + length <= Buffer size

Return value

Type	Description
number	Length of the data read.

Example

let ss = fileio.createStreamSync(path, "r+");
let num = ss.readSync(new ArrayBuffer(4096), {offset: 1, length: 5, position: 5});

Dir

Manages directories. Before calling a method of the Dir class, use the opendir() method synchronously or asynchronously to create a Dir instance.

read

read(): Promise<Dirent>

Reads the next directory entry. This API uses a promise to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
Promise<Dirent>	Promise used to return the directory entry read.

Example

dir.read().then(function (dirent){
    console.log("Read the next directory entry:"+JSON.stringify(dirent));
}).catch(function(err){
    console.info("Failed to read the next directory entry. Error:"+ err);
});

read

read(callback: AsyncCallback<Dirent>): void

Reads the next directory entry. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.FileManagement.File.FileIO

Parameters

Name	Type	Mandatory	Description
callback	AsyncCallback<Dirent>	Yes	Callback invoked when the next directory entry is asynchronously read.

Example

dir.read(function (err, dirent) {
    if (dirent) {
        // Do something
        console.log("Read the next directory entry:"+JSON.stringify(dirent));
    }
});

readSync

readSync(): Dirent

Synchronously reads the next directory entry.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
Dirent	Directory entry read.

Example

let dirent = dir.readSync();

close⁷⁺

close(): Promise<void>

Closes a directory. This API uses a promise to return the result. After a directory is closed, the file descriptor in Dir will be released and no directory entry can be read from Dir.

System capability: SystemCapability.FileManagement.File.FileIO

Example

dir.close().then(function(err){
    console.info("close dir successfully");
});

close⁷⁺

close(callback: AsyncCallback<void>): void

Closes a directory. This API uses an asynchronous callback to return the result. After a directory is closed, the file descriptor in Dir will be released and no directory entry can be read from Dir.

System capability: SystemCapability.FileManagement.File.FileIO

Example

dir.close(function(err){
    console.info("close dir successfully");
});

closeSync

closeSync(): void

Closes a directory. After a directory is closed, the file descriptor in Dir will be released and no directory entry can be read from Dir.

System capability: SystemCapability.FileManagement.File.FileIO

Example

dir.closeSync();

Dirent

Provides information about files and directories. Before calling a method of the Dirent class, use the dir.read() method synchronously or asynchronously to create a Dirent instance.

System capability: SystemCapability.FileManagement.File.FileIO

Attributes

Name	Type	Readable	Writable	Description
name	string	Yes	No	Directory entry name.

isBlockDevice

isBlockDevice(): boolean

Checks whether this directory entry 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

Type	Description
boolean	Whether the directory entry is a block special file.

Example

let dir = fileio.opendirSync(path);
let isBLockDevice = dir.readSync().isBlockDevice();

isCharacterDevice

isCharacterDevice(): boolean

Checks whether a directory entry 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

Type	Description
boolean	Whether the directory entry is a character special file.

Example

let dir = fileio.opendirSync(path);
let isCharacterDevice = dir.readSync().isCharacterDevice();

isDirectory

isDirectory(): boolean

Checks whether a directory entry is a directory.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the directory entry is a directory.

Example

let dir = fileio.opendirSync(path);
let isDirectory = dir.readSync().isDirectory();

isFIFO

isFIFO(): boolean

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

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the directory entry is a FIFO.

Example

let dir = fileio.opendirSync(path);
let isFIFO = dir.readSync().isFIFO();

isFile

isFile(): boolean

Checks whether a directory entry is a regular file.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the directory entry is a regular file.

Example

let dir = fileio.opendirSync(path);
let isFile = dir.readSync().isFile();

isSocket

isSocket(): boolean

Checks whether a directory entry is a socket.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the directory entry is a socket.

Example

let dir = fileio.opendirSync(path);
let isSocket = dir.readSync().isSocket();

isSymbolicLink

isSymbolicLink(): boolean

Checks whether a directory entry is a symbolic link.

System capability: SystemCapability.FileManagement.File.FileIO

Return value

Type	Description
boolean	Whether the directory entry is a symbolic link.

Example

let dir = fileio.opendirSync(path);
let isSymbolicLink = dir.readSync().isSymbolicLink();

File Management

Modules to Import

Guidelines

fileio.stat

fileio.stat

fileio.statSync

fileio.opendir

fileio.opendir

fileio.opendirSync

fileio.access

fileio.access

fileio.accessSync

fileio.close7+

fileio.close7+

fileio.closeSync

fileio.copyFile

fileio.copyFile

fileio.copyFileSync

fileio.mkdir

fileio.mkdir

fileio.mkdirSync

fileio.open7+

fileio.open7+

fileio.openSync

fileio.read

fileio.read

fileio.readSync

fileio.rmdir7+

fileio.rmdir7+

fileio.rmdirSync7+

fileio.unlink

fileio.unlink

fileio.unlinkSync

fileio.write

fileio.write

fileio.writeSync

fileio.hash

fileio.hash

fileio.chmod7+

fileio.chmod7+

fileio.chmodSync7+

fileio.fstat7+

fileio.fstat7+

fileio.fstatSync7+

fileio.ftruncate7+

fileio.ftruncate7+

fileio.ftruncateSync7+

fileio.truncate7+

fileio.truncate7+

fileio.truncateSync7+

fileio.readText7+

fileio.readText7+

fileio.readTextSync7+

fileio.lstat7+

fileio.lstat7+

fileio.lstatSync7+

fileio.rename7+

fileio.rename7+

fileio.renameSync7+

fileio.fsync7+

fileio.fsync7+

fileio.fsyncSync7+

fileio.fdatasync7+

fileio.fdatasync7+

fileio.fdatasyncSync7+

fileio.symlink7+

fileio.symlink7+

fileio.symlinkSync7+

fileio.chown7+

fileio.chown7+

fileio.chownSync7+

fileio.mkdtemp7+

fileio.mkdtemp7+

fileio.mkdtempSync7+

fileio.fchmod7+

fileio.fchmod7+

fileio.fchmodSync7+

fileio.createStream7+

fileio.createStream7+

fileio.createStreamSync7+

fileio.close⁷⁺

fileio.close⁷⁺

fileio.open⁷⁺

fileio.open⁷⁺

fileio.rmdir⁷⁺

fileio.rmdir⁷⁺

fileio.rmdirSync⁷⁺

fileio.chmod⁷⁺

fileio.chmod⁷⁺

fileio.chmodSync⁷⁺

fileio.fstat⁷⁺

fileio.fstat⁷⁺

fileio.fstatSync⁷⁺

fileio.ftruncate⁷⁺

fileio.ftruncate⁷⁺

fileio.ftruncateSync⁷⁺

fileio.truncate⁷⁺

fileio.truncate⁷⁺

fileio.truncateSync⁷⁺

fileio.readText⁷⁺

fileio.readText⁷⁺

fileio.readTextSync⁷⁺

fileio.lstat⁷⁺

fileio.lstat⁷⁺

fileio.lstatSync⁷⁺

fileio.rename⁷⁺

fileio.rename⁷⁺

fileio.renameSync⁷⁺

fileio.fsync⁷⁺

fileio.fsync⁷⁺

fileio.fsyncSync⁷⁺

fileio.fdatasync⁷⁺

fileio.fdatasync⁷⁺

fileio.fdatasyncSync⁷⁺

fileio.symlink⁷⁺

fileio.symlink⁷⁺

fileio.symlinkSync⁷⁺

fileio.chown⁷⁺

fileio.chown⁷⁺

fileio.chownSync⁷⁺

fileio.mkdtemp⁷⁺

fileio.mkdtemp⁷⁺

fileio.mkdtempSync⁷⁺

fileio.fchmod⁷⁺

fileio.fchmod⁷⁺

fileio.fchmodSync⁷⁺

fileio.createStream⁷⁺

fileio.createStream⁷⁺

fileio.createStreamSync⁷⁺

fileio.fdopenStream⁷⁺

fileio.fdopenStream⁷⁺

fileio.fdopenStreamSync⁷⁺

fileio.fchown⁷⁺

fileio.fchown⁷⁺

fileio.fchownSync⁷⁺

fileio.lchown⁷⁺

fileio.lchown⁷⁺

fileio.lchownSync⁷⁺

fileio.createWatcher⁷⁺

Watcher⁷⁺

stop⁷⁺

stop⁷⁺

close⁷⁺

close⁷⁺

flush⁷⁺

flush⁷⁺

flushSync⁷⁺

write⁷⁺

write⁷⁺

writeSync⁷⁺

read⁷⁺

read⁷⁺

readSync⁷⁺

close⁷⁺

close⁷⁺