Skip to content

Latest commit

 

History

History
151 lines (103 loc) · 3.17 KB

07.5.md

File metadata and controls

151 lines (103 loc) · 3.17 KB

#7.5 Files File is must-have object in every single computer device, and web applications also have many usage with files. In this section, we're going to learn how to operate files in Go.

##Directories Most of functions of file operations is in package os, here are some functions about directories:

  • func Mkdir(name string, perm FileMode) error

    Create directory with name, perm is permission, like 0777.

  • func MkdirAll(path string, perm FileMode) error

    Create multiple directories according to path, like astaxie/test1/test2.

  • func Remove(name string) error

    Remove directory with name, it returns error if it's not directory or not empty.

  • func RemoveAll(path string) error

    Remove multiple directories according to path, it will not be deleted if path is a single path.

Code sample:

package main

import (
	"fmt"
	"os"
)

func main() {
	os.Mkdir("astaxie", 0777)
	os.MkdirAll("astaxie/test1/test2", 0777)
	err := os.Remove("astaxie")
	if err != nil {
		fmt.Println(err)
	}
	os.RemoveAll("astaxie")
}

##Files ###Create and open files Two functions to create files:

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

    Create file with name and return a file object with permission 0666 and read-writable.

  • func NewFile(fd uintptr, name string) *File

    Create file and return a file object.

Two functions to open files:

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

    Open file with name with read-only permission, it calls OpenFile underlying.

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

    Open file with name, flag is open mode like read-only, read-write, perm is permission.

###Write files Functions for writing files:

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

    Write byte type content to file.

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

    Write byte type content to certain position of file.

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

    Write string to file.

Code sample:

package main

import (
	"fmt"
	"os"
)

func main() {
	userFile := "astaxie.txt"
	fout, err := os.Create(userFile)		
	if err != nil {
		fmt.Println(userFile, err)
		return
	}
	defer fout.Close()
	for i := 0; i < 10; i++ {
		fout.WriteString("Just a test!\r\n")
		fout.Write([]byte("Just a test!\r\n"))
	}
}

###Read files Functions for reading files:

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

    Read data to b.

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

    Read data from position off to b.

Code sample:

package main

import (
	"fmt"
	"os"
)

func main() {
	userFile := "asatxie.txt"
	fl, err := os.Open(userFile)		
	if err != nil {
		fmt.Println(userFile, err)
		return
	}
	defer fl.Close()
	buf := make([]byte, 1024)
	for {
		n, _ := fl.Read(buf)
		if 0 == n {
			break
		}
		os.Stdout.Write(buf[:n])
	}
}

###Delete files Go uses same function for removing files and directories:

  • func Remove(name string) Error

    Remove file or directory with name.( name ends with / means directory )

##Links