Understand the reading, writing and creation of files in go language

Catalog

1. Opening and closing of files

1.1 os.open

1.2 os.OpenFile() Open file in specified mode

2. File reading

2.1 Read the data in the file by opening the file

2.2 Use bufio Read the whole line of the file

3. Write file operation

3.1 file.Write And file.WriteString

3.2 bufio.NewWriter

3.3 ioUtil Tool class

1. Opening and closing of files 1.1 os.open

os.open Function can open a file call close() Method Close file

// Open file open, err := os.Open("./1.text")if err != nil {// Print exception information fmt.Println("open file err", err)}fmt.Println(" File acquisition completed ")// No exception occurred , Close file open.Close()

To prevent forgetting to close the file , Usually, the code to close the file is written in defer in

// Open file open, err := os.Open("./1.text")defer func() {if open != nil {// Close file open.Close()}}()if err != nil {// Print exception information fmt.Println("open file err", err)}fmt.Println(" File acquisition completed ")1.2 os.OpenFile() Open file in specified mode func OpenFile(name string, flag int, perm FileMode) (*File, error) { ...}

among ：

name： The name of the file to open flag： Open file mode . There are several modes ：

Pattern meaning

os.O_WRONLY	Just write
os.O_CREATE	create a file
os.O_RDONLY	read-only
os.O_RDWR	Reading and writing
os.O_TRUNC	Empty
os.O_APPEND	Additional

perm： File permissions , An octal number .r（ read ）04,w（ Write ）02,x（ perform ）01.

2. File reading 2.1 Read the data in the file by opening the file // First you need to open a file open, err := os.Open("./1.text")defer func() {e := recover()if e != nil {fmt.Println(" An exception occurred when opening the file ", e)}}()if err != nil {// If there is any abnormality There's no need to go down Throw out panic(err)}// If there is no abnormality // establish Byte slice bytes := make([]byte, 1024)defer func() {e := recover()if e != nil {fmt.Println(" An exception occurred while reading the file ", e)}}()for {// Circle reading _, err := open.Read(bytes)if err != nil {panic(err)}// Print the results fmt.Println(string(bytes))}2.2 Use bufio Read the whole line of the file

bufio Is in file It encapsulates a layer of API , Support more functions

// Similarly, first open a file file, err := os.Open("./1.text")defer recover()if err != nil {panic(" An exception occurred while opening the file ")}// Encapsulated in the bufioreader := bufio.NewReader(file)defer recover()for {// Read the specified string and change to another line line, _, err := reader.ReadLine()if err != nil {if err == io.EOF {fmt.Println(" The file is read and written ")break}panic(" File reading exception ")}fmt.Println(string(line))}fmt.Println(" End of program running ")func main() {file, err := os.OpenFile("xx.txt", os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0666)}3. Write file operation

Whether it is file reading or file writing You need to open the file first Do it again

3.1 file.Write And file.WriteString// So let's open the file O_RDWR read-write permission O_TRUNC Empty files 0 Start with octal 666 Express Current user Current group Other users Read and write permissions file, err := os.OpenFile("1.text", os.O_RDWR|os.O_TRUNC, 0666)if err != nil {fmt.Printf(" Exception in opening file %v", err)}defer file.Close()// return Bytes written write, err := file.Write([]byte(" Test file write \n"))file.WriteString(" Write the entire string at once ")if err != nil {fmt.Println(err)}fmt.Println(write)3.2 bufio.NewWriter// Based on cache operation file, err := os.OpenFile("2.text", os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0666)if err != nil {panic(err)}defer func() {file.Close()if e := recover(); e != nil {fmt.Printf(" abnormal : Exception in opening file %v", e)}}()// Use bufio Based on cache operation io flow // Need to One io Interface package Writer Interface implementation class and file It's time to Method writer := bufio.NewWriter(file)writer.WriteString(" Write cache string contents 2")// You need to refresh the data in the cache to the hard disk writer.Flush()

3.3 ioUtil Tool class // Use tool class Open file , Write the file at one go err := ioutil.WriteFile("3.text", []byte(" Tool class writes content "), 0666)if err != nil {fmt.Println(" The program runs abnormally ", err)}

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