Golang four ways to manipulate files

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Golang append content to end of file

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Golang read and write files, many tutorials on the web
But today there is a need to append the content to the end of the file
Google for a long time, did not find
Studied the file library for a while, finally let me find (blindfolded) the additional method
The main 2 functions are:

func (f *File) Seek(offset int64, whence int) (ret int64, err error)
func (f *File) WriteAt(b []byte, off int64) (n int, err error)

• Seek () to find the offset at the end of the file
• Writeat () starts writing from the offset

Here are the chestnuts:
// fileName:文件名字(带全路径)// content: 写入的内容func appendToFile(fileName string, content string) error { // 以只写的模式，打开文件 f, err := os.OpenFile(fileName, os.O_WRONLY, 0644) if err != nil { fmt.Println("cacheFileList.yml file create failed. err: " + err.Error()) } else { // 查找文件末尾的偏移量 n, _ := f.Seek(0, os.SEEK_END) // 从末尾的偏移量开始写入内容 _, err = f.WriteAt([]byte(content), n) } defer f.Close() return err}

Take it, don't hesitate:)
Feel that the current domestic Golang document blog is still a little lack of points,
I hope we usually have any experience in coding to share with each other,
Make Golang more and more useful!

2016/08/31 Record:
I am a fool, obviously the simplest way can be achieved:
f, err := os.OpenFile(fileName, os.O_WRONLY|os.O_APPEND, 0666)
Open the file in the form of write and append ...

There are four ways to manipulate files below

Package Main

Import (
"Bufio"//Cache IO
"FMT"
"Io/ioutil"//io Toolkit
"IO"
"OS"
)

Func Check (e error) {
If E! = Nil {
Panic (e)
}
}

/**
* Determine if a file exists return true does not exist return false
*/
Func checkfileisexist (filename string) (bool) {
var exist = true;
If _, Err: = OS. Stat (filename); Os. Isnotexist (Err) {
exist = false;
}
return exist;
}

/**
from:http://www.isharey.com/?p=143
*/

Func Main () {
var wiretestring = "Test n"
var filename = "./output1.txt";
var f *os. File
var err1 error;
/***************************** first way: Using IO. WriteString writing to File ***********************************************/
If checkfileisexist (filename) {//If the file exists
F, err1 = OS. OpenFile (filename, os. O_append, 0666)//Open File
Fmt. Println ("file exists");
}else {
F, err1 = OS. Create (filename)//File creation
Fmt. PRINTLN ("File does not exist");
}
Check (ERR1)
N, err1: = Io. WriteString (f, wiretestring)//write to file (string)
Check (ERR1)
Fmt. Printf ("write%d bytes n", n);

/***************************** second way: Use Ioutil. WriteFile writing to File ***********************************************/
var D1 = []byte (wiretestring);
ERR2: = Ioutil. WriteFile ("./output2.txt", D1, 0666)//write file (byte array)
Check (ERR2)

/***************************** Third Way: Write files using file (write,writestring) ********************************************* **/
F, ERR3: = OS. Create ("./output3.txt")//File creation
Check (ERR3)
Defer F.close ()
N2, Err3: = F.write (D1)//write to file (byte array)
Check (ERR3)
Fmt. Printf ("write%d bytes n", N2)
N3, Err3: = f.writestring ("WRITESN")//write to file (byte array)
Fmt. Printf ("write%d bytes n", N3)
F.sync ()

 /***************************** Fourth Way:   use Bufio. Newwriter Write file ***********************************************/
 w: = Bufio. Newwriter (f)  //creates a new Writer object
 n4, Err3: = w.writestring ("Bufferedn")
 fmt. Printf ("write%d bytes n", N4)
 w.flush ()
 f.close ()
}