Append content to a file

The fs.open or File.open function is used to open a file and return a std.fs.File instance, with flag argument you can specify the file open mode.

• The fs.APPEND flag is used to open the file in append mode.
• The fs.CREATE flag is used to create a new file if the file does not exist.

Then use write_string method to write the string content to the file.

Navi Code

use std.fs;

fn main() throws {
    let f = try fs.open("output.txt", flag: fs.APPEND | fs.CREATE);
    defer {
        try! f.close();
    }
    try f.write_string("Hello, world!\n");
    try f.write_string("This is next line!\n");
}

The above code will append the content to the file output.txt. If the file does not exist, it will create a new file.

After running the above code, the content of the file output.txt will be:

Hello, World!
This is next line!