Parse the fs read/write of NodeJs and delete the mobile listener

This article mainly introduces the fs read/write deletion mobile listening of NodeJs, which is very good and has reference value. If you need it, you can refer to the next article to introduce the fs read/write deletion mobile listening of NodeJs, it is very good and has reference value. If you need it, you can refer to it.

NodeJs version: 4.4.4

Fs

The file system module is a collection of standard POSIX file I/O operations. The methods in the Node. js File System (fs module) module are both asynchronous and synchronous.

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Create a readable stream and a write stream. Pipeline pipe.

Var fileReadStream = fs. createReadStream (sourcePath); var fileWriteStream = fs. createWriteStream (targetPath); fileReadStream. pipe (fileWriteStream); // The Listener closes the event and the execution is completed. on ('close', function () {console. log ('moved successfully! ');})

Read a file (fs. readFile)

Definition: fs. readFile (filename [, options], callback)

Parameters:

• Filename: {String} file name/file path

• Options: {Object} (optional)
  

Encoding: {String | Null} default = null encoding method

Flag: {String} default = 'R' file opening behavior (writable, readable, etc)

• Callback: {Function}
  

Var fs = require ('fs'); // read the file fs. readFile ('.. /lianxi/child_process.js ', {encoding: 'utf-8', flag: 'R'}, function (err, data) {if (err) throw err; console. log (data );});

If the encoding method is not set, the Read File is returned as a buffer.

If it is set to UTF-8, the returned result is in the string format. As follows:

var child_process = require('child_process');...

Write a file (fs. writeFile)

Definition: fs. writeFile (filename, data [, options], callback)

Parameters:

• Filename: {String}
  

• Data: {String | Buffer}
  

• Options: {Object}
  

Encoding: {String | Null} default = 'utf8'
Mode: {Number} default = 438 (aka 0666 in Octal)
Flag: {String} default = 'W'

• Callback {Function}
  

// Write File fs. writeFile ('.. /lianxi/child_process.js ',' [zqz] data string or buffer ', {encoding: 'utf8', mode: 438, flag: 'W '}, function (err ){})

Note:Asynchronous file writing. If the file already exists, replace it.

Open a file (fs. open)

Definition: fs. open (path, flags [, mode], callback)

Parameters:

• Path: File/file path

• Flags: file opening Behavior

• Mode: sets the file mode (permission). The default permission for file creation is 0666 (readable and writable ).

• Callback: callback function
  

// Open the file fs. open ('../lianxi/child_process.js', 'r + ', 0666, function (err, data ){})

Add data to a file (fs. appendFile)

Definition: fs. appendFile (filename, data [, options], callback)

Parameters:

• Filename: {String}
  

• Data: {String | Buffer}
  

• Options: {Object}
  

Encoding {String | Null} default = 'utf8'
Mode {Number} default = 438 (aka 0666 in Octal)
Flag {String} default = 'A'

• Callback {Function}
  

// Add data to the file fs. appendFile ('.. /lianxi/child_process.js ', 'asynchronously added string or buffer', {encoding: 'utf8', mode: 438, flag: 'A'}, function (err) {});

Note:Asynchronously add data to a file. If the file does not exist, a file is created.

Delete a file (fs. unlink)

Definition: fs. unlink (path, callback)

Var fs = require ('fs'); fs. unlink ('. /t/index.html ', function (err) {if (err) throw err; console. log ('success ')})

Create a file (fs. open)

Definition: fs. open (path, flags [, mode], callback)

You can also use fs. open to create a file.

fs.open("test.txt", "w",function (err) {});

Delete a folder (fs. rmdir)

Definition: fs. rmdir (path, callback)

Fs. rmdir ('./t/A', function (err) {if (err) throw err; console. log ('success ')})

Create a folder (fs. mkdir)

Definition: fs. mkdir (path [, mode], callback)

Parameter: the default mode is to 0777.

Fs. mkdir ('./t/A', 0777, function (err) {if (err) throw err; console. log ('success ')})

File listening (fs. watch fs. watchFile)

Definition: fs. watch (filename [, options] [, listener])
Definition: fs. watchFile (filename [, options], listener)

fs.watch('test.js', function (event, filename) {});fs.watchFile('test.js', function(curr, prev){});

Flags

Flag	Description
R	Open the file in Read mode. If the file does not exist, an exception is thrown.
R +	Open a file in read/write mode. If the file does not exist, an exception is thrown.
Rs	Read files in synchronous mode.
Rs +	Read and Write files in synchronous mode.
W	Open the file in write mode. If the file does not exist, it is created.
Wx	Similar to 'w', but if the file path exists, the file fails to be written.
W +	Open the file in read/write mode. If the file does not exist, it is created.
Wx +	Similar to 'W + ', but if the file path exists, the file read/write fails.
A	Open the file in append mode. If the file does not exist, it is created.
Ax	Similar to 'A', but if the file path exists, the file append fails.
A +	Open the file in read append mode. If the file does not exist, it is created.
Ax +	Similar to 'a + ', but if the file path exists, the file read and append fails.

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