Node.js - fs File Operations

process module at the time of use without the need require () function to load the module, it can be used directly.

fs module , when in use, must () function to load the module through the require, before use.

The reason: process modules are global module, the module rather than fs global module. Global module can be used directly, rather than via the global module needs require ( '') to load the module.

 

First, the implementation file write operations

1  // 1. Load module file operation, fs module 
2  var FS = the require ( 'FS' );
 . 3  
. 4  // 2. implement file write operations 
. 5  var MSG = "Hello World, Hello world" ;
 . 6  
. 7  / / call fs.writeFile () to write files 
. 8  // fs.writeFile () is an asynchronous method 
. 9  // fs.writeFile ( 'write the file path' and 'data to be written', 'document encoding formats' 'callback') 
10 fs.writeFile ( 'hello.txt', MSG, 'UTF8', (err) => {
 . 11      // if err === null, indicates that the file is written 
12      // long as there is not err null, it means write to file failed! 
13      IF (ERR) {
 14         console.log ( 'Error writing to file pull-specific error:!' + ERR)
 15      } the else {
 16          console.log ( 'OK' );
 . 17      }
 18 is });

Second, the implementation file read operation

1  // 1. Load module file operation, fs module 
2  var FS = the require ( 'FS' );
 . 3  
. 4  // 2. calls fs.readFile () method to read the file 
. 5  // fs.readFile ( 'read path to the file ',' file encoding format '' callback ') 
6  // read the document, if the transmission encoding format, the callback function will be converted to the default string data, or data parameters Buffer is a data object which is stored in a one byte (byte array understood) 
7  // converts Buffer string object, call toString () method 
. 8  
. 9 fs.readFile ( './ hello.txt ',' UTF8 ', (ERR, Data) => {
 10      IF (ERR) {
 . 11          the throw ERR;
 12 is      } the else {
 13 is          the console.log (Data);
14     }
15 });

 

Routing Problem 1. Read file

 ./ relative path, relative path node command execution, rather than relative to the js file is being performed to find hello.txt

./ relative path to solve the problem of reading in the file

Solution : Use __dirname, __ filename

__dirname: said directory js file currently being executed is located

___filename: express, full path to the js file that is currently being executed

 

// console.log(__dirname);   C:\Users\zhuyujie\Desktop\nodejs\1.fs

// console.log(__filename);   C:\Users\zhuyujie\Desktop\nodejs\1.fs\2.fs_readFile.js

Note: __dirname, not global filename ___

 

Path above code should be modified to:

. 1  var FS = the require ( 'FS' );
 2  
. 3  // var filename = __dirname + '\\' + 'hello.txt' (not recommended) 
. 4  
. 5  // recommended path by a path module for splicing 
. 6  var path = the require ( 'path' );
 . 7  
. 8  var filename = path.join (__ dirname, 'hello.txt' )
 . 9  
10  // the console.log (filename); 
. 11  
12 is fs.readFile (filename, 'UTF8', (ERR, Data) => {
 13 is      IF (ERR) {
 14          the throw ERR;
 15      }
 16      the console.log (Data);
 . 17 
18 });

 Third, create a folder

. 1  var FS = the require ( 'FS' );
 2  
. 3 fs.mkdir ( 'Test-mkdir', (ERR) => {
 . 4  IF (ERR) {
 . 5      the console.log ( 'create the directory wrong, details' + ERR );
 . 6 } the else {
 . 7      the console.log ( 'create the directory success' );
 8  }
 9 });