File Handling in Go: Read, Write, and Manage Files

In Go, file handling is straightforward and powerful. You can create, read, write, and manage files using standard packages like os, io, and ioutil (deprecated but still common). Understanding how to work with files is essential when building CLI tools, web servers, or any application that deals with local data.

In this article, you’ll learn:

How to create and write to a file
How to read a file
Appending data to files
Working with directories
Checking if a file exists
Best practices and error handling

Creating and Writing to a File

To create and write content to a file:

func main() {
    content := []byte("Hello, file!")

    err := os.WriteFile("example.txt", content, 0644)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("File written successfully")
}

os.WriteFile creates the file if it doesn't exist and replaces it if it does.

Reading a File

To read the entire content of a file:

func main() {
    data, err := os.ReadFile("example.txt")
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("File content:", string(data))
}

Appending to a File

If you want to add content to an existing file without overwriting it:

func main() {
    f, err := os.OpenFile("example.txt", os.O_APPEND|os.O_WRONLY, 0644)
    if err != nil {
        log.Fatal(err)
    }
    defer f.Close()

    if _, err := f.WriteString("\nThis is appended."); err != nil {
        log.Fatal(err)
    }

    fmt.Println("Appended successfully")
}

Working with Directories

Create a new folder:

err := os.Mkdir("myfolder", 0755)

Create nested folders:

err := os.MkdirAll("path/to/folder", 0755)

List files in a folder:

files, err := os.ReadDir(".")
for _, file := range files {
    fmt.Println(file.Name())
}

Check if a File Exists

func fileExists(filename string) bool {
    _, err := os.Stat(filename)
    return !os.IsNotExist(err)
}

Deleting a File or Folder

err := os.Remove("example.txt")              // delete file
err := os.RemoveAll("path/to/folder")        // delete folder and contents

Best Practices

Always handle file errors (file not found, permissions)
Use defer f.Close() after opening files
Use os.ReadFile and os.WriteFile for simple tasks
Use buffered I/O (like bufio) for large files

Conclusion

File handling in Go is clean and efficient. Whether you're reading logs, saving data, or managing folders, the standard library provides everything you need. Understanding how to work with files opens the door to building robust and real-world applications in Go.

Next, we’ll look into working with JSON in Go — another essential skill for building APIs and storing structured data.

Happy coding!

buanacoding