[笔记]Go语言写文件几种方式性能对比

package main
import (
 "fmt"
 "os"
 "time"
)
func benchmarkFileWrite(filename string, n int, index int) (d time.Duration) {
 v := "ni shuo wo shi bu shi tai wu liao le a?"
 os.Remove(filename)
 t0 := time.Now()
 switch index {
 case 0: // open file and write, then close, repeat n times
 for i := 0; i < n; i++ {
 file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
 if err != nil {
 fmt.Println(index, i, "open file failed.", err.Error())
 break
 }
 file.WriteString(v)
 file.WriteString("\n")
 file.Close()
 }
 case 1: // open file and write, defer close, repeat n times
 for i := 0; i < n; i++ {
 file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
 if err != nil {
 fmt.Println(index, i, "open file failed.", err.Error())
 break
 }
 defer file.Close()
 file.WriteString(v)
 file.WriteString("\n")
 }
 case 2: // open file and write n times, then close file
 file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
 if err != nil {
 fmt.Println(index, "open file failed.", err.Error())
 break
 }
 defer file.Close()
 for i := 0; i < n; i++ {
 file.WriteString(v)
 file.WriteString("\n")
 }
 }
 t1 := time.Now()
 d = t1.Sub(t0)
 fmt.Printf("time of way(%d)=%v\n", index, d)
 return d
}
func main() {
 const k, n int = 3, 1000
 d := [k]time.Duration{}
 for i := 0; i < k; i++ {
 d[i] = benchmarkFileWrite("benchmarkFile.txt", n, i)
 }
 for i := 0; i < k-1; i++ {
 fmt.Printf("way %d cost time is %6.1f times of way %d\n", i, float32(d[i])/float32(d[k-1]), k-1)
 }
}

 time of way(0)=38.719386ms
 time of way(1)=31.428677ms
 time of way(2)=17.930829ms
 way 0 cost time is 2.2 times of way 2
 way 1 cost time is 1.8 times of way 2

 time of way(0)=170.003521ms
 1 1021 open file failed. open benchmarkFile.txt: too many open files
 time of way(1)=32.388994ms
 time of way(2)=77.777936ms
 way 0 cost time is 2.2 times of way 2
 way 1 cost time is 0.4 times of way 2

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