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 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) } }
当n=1000时，测试结果如下
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
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(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
