How to Append Data to a File in Go?

Appending to Files in Go

In Go, reading from a local file is straightforward using ioutil.ReadFile. Similarly, writing to a file can be done using ioutil.WriteFile. However, when it comes to appending to an existing file, there is no built-in method that directly handles this.

Solution

To append to a file in Go, you can use the following steps:

1. Open the file using os.OpenFile, specifying the following flags:

   • os.O_APPEND: Enables appending to the file.
   • os.O_WRONLY: Opens the file for writing only.
   • os.O_CREATE: Creates the file if it does not exist.

f, err := os.OpenFile(filename, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
if err != nil {
    panic(err)
}

2. After opening the file, you can write to it using the WriteString method:

if _, err = f.WriteString(text); err != nil {
    panic(err)
}

3. Finally, remember to close the file to release the associated file descriptor:

defer f.Close()

By following these steps, you can effectively append data to an existing file in Go.

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