Title: Tutorial on Node File System
1iFour Consultancy
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2Introduction
- Node.js gives the functionality of File I/O by
providing wrappers around the standard POSIX
functions. In Node.js, File I/O methods can be
performed in both synchronous as well as
asynchronous form depending upon the user
requirements. - The Node.js file system module allows you to work
with the file system on your computer. - To include the File System module, use the
require() method -
- var fs require('fs')
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3Use of File System
- Common use for the File System module
- Read files
- Write files
- Append files
- Delete files
- Rename files
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4Synchronous vs Asynchronous
- Every method in the fs module has synchronous as
well as asynchronous forms. Asynchronous methods
take the last parameter as the completion
function callback and the first parameter of the
callback function as error. It is better to use
an asynchronous method instead of a synchronous
method, as the former never blocks a program
during its execution, whereas the second one does.
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5Node.js Reading File
- Every method in fs module has synchronous and
asynchronous forms. - Asynchronous methods take a last parameter as
completion function callback. Asynchronous method
is preferred over synchronous method because it
never blocks the program execution where as the
synchronous method blocks. - Example
- Create File input.txt
- We are reading this file using node.js
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6Node.js Reading File
- Example Create File main.js
- For Asynchronous read
- var fs require("fs")
- // Asynchronous read
- fs.readFile('input.txt', function (err, data)
- if (err)
- return console.error(err)
-
- console.log("Asynchronous read "
data.toString())
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7Node.js Reading File
- Example Create File main.js
- For Synchronous read
- var data fs.readFileSync('input.html')
- console.log("Synchronous read "
data.toString()) - console.log("Program Ended")
- Open command prompt and run the main.js
- gt node main.js
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8Node.js Writing a file
- Node.js fs.writeFile() function writes data to a
file asynchronously with replacing the file in
case of already exists. This function can write
data from string or a buffer. - The encoding option is ignored if data is a
buffer. It defaults encoding is utf8, Default
file mode is 0666 and default flag is used w
means write mode. - 1. path is the filename with path.
- 2. data is the String or buffer to write
- 3. options can be an object which is like
encoding, mode, flag. - 4. callback function takes single parameter err
and used to return errors. - Syntax
- fs.writeFile(filename, data, options,
callback)
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9Node.js Writing a file
- There are two ways for writing a file in nodejs
- Example Create File main.js
- For Asynchronous Write
- var fs require('fs')
- var content "this is the content in the file"
- fs.writeFile('input.txt', content , (err) gt
- if (err)
- throw err
- console.log('It\'s saved!')
- )
-
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10Node.js Writing a file
- Example Create File main.js
- For Synchronous write
- var fs require('fs')
- var content "We are writing this file
synchronously using node.js" - fs.writeFileSync('input.txt', content)
- console.log("File Written Successfully")
- Open command prompt and run the main.js
- gt node main.js
-
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11Append a File using Nodejs
- To append data to file in Node.js, use Node FS
appendFile() function for asynchronous file
operation or Node FS appendFileSync() function
for synchronous file operation. - filepath is a String that specifies file path
- data is what you append to the file
- options to specify encoding/mode/flag
- Syntax
- fs.appendFile(filepath, data, options,
callback_function) - fs.appendFileSync(filepath, data, options)
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12Append a File using Nodejs
- There are two ways for Appending a file using
nodejs - Example Create File main.js
- For Asynchronous Append
- var fs require('fs')
- new_data "This data will be appended at the
end of the file." - fs.appendFile('input.txt', new_data , (err) gt
- if(err)
- throw err
- console.log('The new_content was appended
successfully') - )
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13Append a File using Nodejs
- Example Create File main.js
- For Synchronous Append
- var fs require('fs')
- var content "We are Appending this file
synchronously using node.js" - fs.appendFileSync('input.txt', content)
- console.log("File Appended Successfully")
- Open command prompt and run the main.js
- gt node main.js
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14Rename a File in Nodejs
- To rename file with Node FS, use
fs.rename(new_file_name, old_file_name,
callback_function) for asynchronous file rename
operation and use fs.renameSync(new_file_name,
old_file_name) for synchronous file rename
operation. - new_file_path The new file path you would
like to assign - old_file_path Path to the file whose name is
to be changed - callback_function When file renaming operation
is done, Callback Function is
called with an error object. - Syntax
- fs.rename(new_file_path, old_file_path,
callback_function) - fs.renameSync(new_file_path, old_file_path)
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15Rename a File in Nodejs
- There are two ways for Appending a file using
nodejs - Example Create File main.js
- For Asynchronous Rename
- var fs require('fs')
- fs.rename('input.txt', 'newinput.txt', (err) gt
- if (err)
- throw err
- console.log('File renamed successfully')
- )
- console.log("This method is Asynchronous")
-
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16Rename a File in Nodejs
- Example Create File main.js
- For Synchronous Rename
- var fs require('fs')
- fs.renameSync('input.txt', 'newinput.txt')
- console.log('File renamed successfully')
- console.log("This method is Synchronous")
- Open command prompt and run the main.js
- gt node main.js
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17Delete a File in Nodejs
- To delete a file in Node.js, Node FS unlink(path,
callback) can be used for asynchronous file
operation and unlinkSync(path) can be used for
synchronous file operation. - Syntax
- fs.unlink(filePath, callbackFunction)
- fs.unlinkSync(filePath)
-
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18Delete a File in Nodejs
- There are two ways for Appending a file using
nodejs - Example Create File main.js
- For Asynchronous Delete var fs
require('fs') - var filename 'input.txt'
- fs.unlink(filename, (err) gt
- if (err)
- throw err
- console.log('File deleted successfully')
- )
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19Delete a File in Nodejs
- Example Create File main.js
- For Synchronous Delete
- var fs require('fs')
- var filename 'input.txt'
- fs.unlinkSync(filename)
- console.log('File Deleted Successfully')
- Open command prompt and run the main.js
- gt node main.js
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