Go语言中写文件有多种方式，这里进行如下几种方式的速度对比：
- 打开文件，写入内容，关闭文件。如此重复多次
- 打开文件，写入内容，defer 关闭文件。如此重复多次
- 打开文件，重复多次写入内容，defer 关闭文件
在VMWare下的Ubuntu 14.04下运行的结果表明：
- 方式1速度最慢，但是慢的很稳定
- 方式2比方式1略快，但是重复次数多了后会报错，应该是defer被压栈太多导致系统撑不了太多打开的文件
- 方式3速度约是前两者的2倍，因为减少了很多打开关闭文件的操作
测试代码如下：
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 : // open file and write, then close, repeat n times
for i := ; i < n; i++ {
file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, )
if err != nil {
fmt.Println(index, i, "open file failed.", err.Error())
break
} file.WriteString(v)
file.WriteString("\n")
file.Close()
}
case : // open file and write, defer close, repeat n times
for i := ; i < n; i++ {
file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, )
if err != nil {
fmt.Println(index, i, "open file failed.", err.Error())
break
}
defer file.Close() file.WriteString(v)
file.WriteString("\n")
}
case : // open file and write n times, then close file
file, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, )
if err != nil {
fmt.Println(index, "open file failed.", err.Error())
break
}
defer file.Close() for i := ; 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 = ,
d := [k]time.Duration{}
for i := ; i < k; i++ {
d[i] = benchmarkFileWrite("benchmarkFile.txt", n, i)
} for i := ; i < k-; i++ {
fmt.Printf("way %d cost time is %6.1f times of way %d\n", i, float32(d[i])/float32(d[k-]), k-)
}
}
当n=1000时，测试结果如下
time of way()=.719386ms
time of way()=.428677ms
time of way()=.930829ms
way cost time is 2.2 times of way
way cost time is 1.8 times of way
当n=5000时，测试结果如下（因为方式1报错，所以它的时间是错的）
time of way()=.003521ms
open file failed. open benchmarkFile.txt: too many open files
time of way()=.388994ms
time of way()=.777936ms
way cost time is 2.2 times of way
way cost time is 0.4 times of way