Simple File Writing

The simplest method for writing data to a file is to use one of the writeFile() methods. These methods write the full contents of a string or buffer to a file. The following is the syntax for writeFile() methods:

Click here to view code image

fs.writeFile(path, data, [options], callback)
fs.writeFileSync(path, data, [options])

The path parameter specifies the path to the file, which can be relative or absolute. The data parameter specifies the String or Buffer object that will be written to the file. The optional options parameter is an object that can contain encoding, mode, and flag properties that define the string encoding as well as the mode and flags used when opening the file. The asynchronous method also requires the callback parameter, which will be called when the file write has been completed.

The code in Listing 6.1 shows how to implement a simple asynchronous fileWrite() request to store a JSON string of a config object in a file. Figure 6.1 shows the output of the code in Listing 6.1.

Listing 6.1 file_write.js: Writing a JSON string to a file

Click here to view code image

01 var fs = require('fs'),
02 var config = {
03   maxFiles: 20,
04   maxConnections: 15,
05   rootPath: "/webroot"
06 };
07 var configTxt = JSON.stringify(config);
08 var options = {encoding:'utf8', flag:'w'};
09 fs.writeFile('../data/config.txt', configTxt, options, function(err){
10   if (err){
11     console.log("Config Write Failed.");
12   } else {
13     console.log("Config Saved.");
14   }
15 });

Figure 6.1 Output of file_write.js, writing to a configuration file.