Go language file manipulation code summary

# Create and open files

// A new file can be created in the following two ways:

[

func Create(name string) (file *File, err Error)

]

Creates a new file based on the file name provided, returns 1 file object with default permissions of 0666, returns file objects that are read-write.

[

func NewFile(fd uintptr, name string) *File

]

Creates a file based on the file descriptor, returning 1 file object

// Open the file in the following two ways:

[

func Open(name string) (file *File, err Error)

]

This method opens a file named name, but it is read-only, and the internal implementation actually calls OpenFile.

[

func OpenFile(name string, flag int, perm uint32) (file *File, err Error)

]

Open the file named name, flag is the way to open, read only, read and write, perm is the permission

/ / write file

[

func (file *File) Write(b []byte) (n int, err Error)

]

Write information of type byte to a file

[

func (file *File) WriteAt(b []byte, off int64) (n int, err Error)

]

Starts writing byte type information at the specified location

[

func (file *File) WriteString(s string) (ret int, err Error)

]

Write the string information to a file

/ / read the file

[

func (file *File) Read(b []byte) (n int, err Error)

]

Read the data to b

[

func (file *File) ReadAt(b []byte, off int64) (n int, err Error)

]

Start reading data from off to b

// Delete files

[

func Remove(name string) Error

]

Call this function to delete the file named name

//// Close the file

[

func (file *File)Close()

]

Write files

// code_034_os_write_to_file project main.go
package main

import (
  "fmt"
  "os"
)

func main() {

  // The new file 
  fout, err := os.Create("./createfile.txt")
  if err != nil {
    fmt.Println(err)
    return
  }
  defer fout.Close()

  for i := 0; i < 5; i++ {
    // Remark: windows environment , At the end \r\n To wrap ,linux Under the \n You can 
    outstr := fmt.Sprintf("%s:%d\r\n", "Hello Go", i) //Sprintf Console output with a return value string
    //  Written to the file 
    fout.WriteString(outstr)             //string information 
    fout.Write([]byte("abcd\r\n"))          //byte type 
  }
}

Read the file

// code_035_os_read_from_file project main.go
package main

import (
  "fmt"
  "os"
)

func main() {
  fin, err := os.Open("./open_and_read1.txt")
  if err != nil {
    fmt.Println(err) // If the file does not exist: The system cannot find the file specified.
  }
  defer fin.Close()

  buf := make([]byte, 1024) // Create a slice
  for {
    n, _ := fin.Read(buf) // Read the file 
    if n == 0 {
      break
    }
    fmt.Println(string(buf))
  }

}

The terminal switches to the current directory and executes go run ES133en.go ES135en_ES136en_file_file.txt

// code_036_os_copy_file project main.go
package main

import (
  "fmt"
  "io"
  "os"
)

func main() {
  //  Use the command line to improve copy reuse 
  args := os.Args
  if args == nil || len(args) != 3 {
    fmt.Println("useage : go filename.go src File dstFile")
    return
  }

  srcPath := args[1]
  dstPath := args[2]
  fmt.Printf("srcPath = %s, dstPath = %s\r\n", srcPath, dstPath)

  if srcPath == dstPath {
    fmt.Println(" Source and destination files cannot have the same name ")
  }

  // copy 
  srcFile, err1 := os.Open(srcPath)
  if err1 != nil {
    fmt.Println(err1)
    return
  }
  dstFile, err2 := os.Create(dstPath)
  if err2 != nil {
    fmt.Println(err2)
    return
  }
  read_buf := make([]byte, 1024)
  for {
    // Read the file 
    n, err := srcFile.Read(read_buf) // The length of bytes per file read 
    if err != nil && err != io.EOF {
      fmt.Println(err)
      break
    }
    if n == 0 {
      fmt.Println(" File processing completed ")
      break
    }
    // Write to destination file 

    write_buf := read_buf[:n]
    dstFile.Write(write_buf)
  }
  //  Close the file 
  srcFile.Close()
  dstFile.Close()

}