node.js: fs.writeFile(file, data[, options], callback): Write data to a file asynchronously

fs.writeFile(file, data[, options], callback)

This method writes data to a file asynchronously.

Below table summarizes the arguments of writeFile function.

Argument	Type	Description
file	string or Buffer or URL or integer	Specifies the filename or file descriptor.
data	string or Buffer or Unit8Array	Data to be written to the file
options	string or Object	Below table summarizes the options supported by writeFile method. Option Type Description encoding string Default value is utf8 mode integer Default value is 0o666 flag string Default value is w. 'a' - Open file for appending. The file is created if it does not exist. 'ax' - Like 'a' but fails if the path exists. 'a+' - Open file for reading and appending. The file is created if it does not exist. 'ax+' - Like 'a+' but fails if the path exists. 'as' - Open file for appending in synchronous mode. The file is created if it does not exist. 'as+' - Open file for reading and appending in synchronous mode. The file is created if it does not exist. 'r' - Open file for reading. An exception occurs if the file does not exist. 'r+' - Open file for reading and writing. An exception occurs if the file does not exist. 'rs+' - Open file for reading and writing in synchronous mode. Instructs the operating system to bypass the local file system cache. 'w' - Open file for writing. The file is created (if it does not exist) or truncated (if it exists). 'wx' - Like 'w' but fails if the path exists. 'w+' - Open file for reading and writing. The file is created (if it does not exist) or truncated (if it exists). 'wx+' - Like 'w+' but fails if the path exists.
callback	Function	Cal back function take an argument ‘err’. If any error occurs while writing to a file, then this variable is populated with error information.

                 

Below table summarizes the modes supported by node.js

Constant (mode)	Octal value	Description
fs.constants.S_IRUSR	0o400	read by owner
fs.constants.S_IWUSR	0o200	write by owner
fs.constants.S_IXUSR	0o100	execute/search by owner
fs.constants.S_IRGRP	0o40	read by group
fs.constants.S_IWGRP	0o20	write by group
fs.constants.S_IXGRP	0o10	execute/search by group
fs.constants.S_IROTH	0o4	read by others
fs.constants.S_IWOTH	0o2	write by others
fs.constants.S_IXOTH	0o1	execute/search by others

        

Find the below working application.

HelloWorld.js

var fs = require('fs');

var filePath = 'input.txt';

var data = 'I love you the more in that I believe you had liked me for my own sake and for nothing else.';

fs.writeFile(filePath, data, (err) => {
    if (err) {
        console.log('Error occured while writing data to a file.');
    } else {
        console.log("Content saved successfully.")
    }
});

Output

Content saved successfully.

                                             

Note

a.   The encoding option is ignored if data is a buffer.

Previous                                                 Next                                                 Home