gistfile1.txt

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"time"
)

var allS1OutWriterMap = make(map[string]*bufio.Writer)
var allS1OutFileMap = make(map[string]*os.File)

func main() {
	now := time.Now()
	line := "abcdeabcdeabcdeabcde\n"

	for i := 0; i < 4200; i++ {
		for j := 0; j < 2500; j++ {
			filePath := "D:\\test\\s1out\\" + strconv.Itoa(i) + ".txt"
			writer := allS1OutWriterMap[filePath]
			if writer == nil {
				f, err := os.OpenFile(filePath, os.O_RDWR|os.O_CREATE, 0666)
				if err != nil {
					fmt.Println(err)
					return
				}
				allS1OutFileMap[filePath] = f
				writer = bufio.NewWriter(f)
				allS1OutWriterMap[filePath] = writer
			}
			writer.WriteString(line)
		}
	}
	fmt.Println("\nWrite over - ", time.Since(now))
	// Flush
	for key := range allS1OutWriterMap {
		err := allS1OutWriterMap[key].Flush()
		if err != nil {
			fmt.Println(err)
		}
	}
	fmt.Println("\nFlush over - ", time.Since(now))
	// Close
	for key := range allS1OutFileMap {
		err := allS1OutFileMap[key].Close()
		if err != nil {
			fmt.Println(err)
		}
	}
	fmt.Println("\nClose over - ", time.Since(now))
}