Home > Articles > Web Development

  • Print
  • + Share This
Like this article? We recommend

Using open()

The open() method opens a file by passing a file name to the method (or path string), along with how to open the file using a flag as the second parameter. The flags available for use with this method are the following:

Flag Description

r

Open for reading. An exception occurs if the file does not exist.

r+

Open for reading and writing. An exception occurs if the file does not exist.

rs

Open for reading in synchronous mode, which instructs the operating system to bypass the system cache. This is mostly used for opening files on NFS mounts; it does not make open() a synchronous method.

rs+

Open for reading and writing in synchronous mode.

w

Open for writing. If the file does not exist, it is created. If the file already exists, it is truncated.

wx

Similar to the w flag, but the file is opened in exclusive mode. Exclusive mode ensures that the files are newly created.

w+

Open for reading and writing. If the file does not exist, it is created. If the file already exists, it is truncated.

wx+

Similar to the w+ flag, but the file is opened in exclusive mode.

a

Open for appending. If the file does not exist, it is created.

ax

Similar to the a flag, but the file is opened in exclusive mode.

a+

Open for reading and appending. If the file does not exist, it is created.

ax+

Similar to the a+ flag, but the file is opened in exclusive mode.

The third argument to the open() method is the optional mode (defaults to 0666) argument, whereas the final argument is a callback function. The callback function takes the err object and file descriptor as arguments. An example appears below:

var fs = require("fs");
var path = "c:\\Temp\\Test.txt";

fs.open(path, "w+", function(error, fd) {
  if (error) {
    console.error("open error:  " + error.message);
  } else {
    console.log("Successfully opened " + path);
  }
});
  • + Share This
  • 🔖 Save To Your Account