Like this article? We recommend
Like this article? We recommend
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);
}
});