What is Golang ioutil?
ioutil is a Golang (Go) package that provides I/O utility functions. It is often used with the OS package to provide additional methods of handling I/O, like files.
Syntax
| Syntax | What it does |
|---|---|
func ReadFile(filename string) ([]byte, error) |
Reads the file named by filename and returns the contents. |
func ReadAll(r io.Reader) ([]byte, error) |
Reads from the io.Reader r until an error or EOF, then it returns the content. |
func ReadDir(dirname string) ([]os.FileInfo, error) |
Reads the directory named by dirname and returns a list of directory entries sorted by filename. |
func TempFile(dir, pattern string) (f *os.File, err error) |
Creates a new temporary file in the directory dir, opens the file for reading and writing, and returns the resulting *os.File. |
func TempDir(dir, pattern string) (name string, err error) |
Creates a new temporary directory in the directory dir. |
func WriteFile(filename string, data []byte, perm os.FileMode) error |
Writes data to a file named by filename. If the file does not exist, WriteFile creates it with permissions perm; otherwise, WriteFile truncates it before writing. |
Example
In the example below, we use ReadFile to read a file and print its content. We then use WriteFile to create and write to a new file. Finally, we read and print all the files in the current directory.
main.go
example.txt
package mainimport ("fmt""io/ioutil")// Helper function for logging errorsfunc check(err error) {if err != nil {panic(err)}}func main() {// Reading content from file.content, err := ioutil.ReadFile("example.txt")check(err)fmt.Printf("File contents: %s\n", content)// Writing to a new file newFile.txt.data := []byte("Hello, Educative!")err = ioutil.WriteFile("newFile.txt", data, 0644)check(err)// Printing all files in the current directory.// Notice a new newFile.txt file (that we created above).files, err := ioutil.ReadDir(".")check(err)fmt.Println("Files in the current directory:")for _, file := range files {fmt.Println(file.Name())}}
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