Keep x backup files

app.config

<?xml version="1.0" encoding="utf-8"?>
<config>
    <general>
        <export-folder></export-folder>
        <files2keep>2</files2keep>
    </general>
</config>

Keep x backup files.go

/*
Copyright (c) 2018, Gheorghita Stanciu gheorghita(dot)stanciu(at)gmail(dot)com
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met: 
1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer. 
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution. 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies, 
either expressed or implied, of the FreeBSD Project.
*/

package main

import (
	"encoding/xml"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"sort"
	"time"
)

type configuration struct {
	XMLName xml.Name `xml:"config"`
	General configurationGeneral
}

type configurationGeneral struct {
	XMLName      xml.Name `xml:"general"`
	ExportFolder string   `xml:"export-folder"`
	Files2Keep   int      `xml:"files2keep"`
}

var (
	config = configuration{}
)

func main() {
	t := time.Now()
	sData := t.Format("20060102")

	logFile, err := os.OpenFile(fmt.Sprintf("logs/cleanbackups_%s.txt", sData), os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
	if err != nil {
		log.Println(err)
		return
	}
	defer logFile.Close()

	mw := io.MultiWriter(os.Stdout, logFile)

	log.SetOutput(mw)

	cfgFile := "./app.config"
	err = config.readFromFile(cfgFile)
	if err != nil {
		log.Println(err)
		return
	}

	directory := getAbsPath(config.General.ExportFolder)

	log.Printf("Cleaning old files from \"%s\"\n", directory)
	log.Printf("Will keep the last %d files.", config.General.Files2Keep)

	err = cleanDir(directory, "exp_svm_*.zip")
	if err != nil {
		log.Fatal(err)
		return
	}

	err = cleanDir(directory, "exp_svm_*.dmp")
	if err != nil {
		log.Fatal(err)
		return
	}

	err = cleanDir(directory, "exp_officenet_*.zip")
	if err != nil {
		log.Fatal(err)
		return
	}

	err = cleanDir(directory, "exp_officenet_*.dmp")
	if err != nil {
		log.Fatal(err)
		return
	}

	log.Println("Process finished.")
}

func getAbsPath(dir string) string {
	directory := dir

	if len(directory) == 0 {
		directory = "./"
	}

	directory, err := filepath.Abs(directory)
	if err != nil {
		log.Fatal(err)
		return "./"
	}

	if directory[len(directory)-1:] == "/" || directory[len(directory)-1:] == "\\" {
		directory = directory[0 : len(directory)-1]
	}

	return directory
}

func cleanDir(directory, pattern string) error {
	files, err := filepath.Glob(directory + "/" + pattern)
	if err != nil {
		return err
	}

	layout := "02.01.2006"

	sort.Slice(files, func(i, j int) bool {
		a := files[i]
		b := files[j]

		if len(a) >= 14 && len(b) >= 14 {
			sda := a[len(a)-14 : len(a)-4]
			sdb := b[len(b)-14 : len(b)-4]

			da, _ := time.Parse(layout, sda)
			db, _ := time.Parse(layout, sdb)

			return da.After(db)
		}

		return files[i] < files[j]
	})

	for i, f := range files {
		if i > config.General.Files2Keep-1 {
			log.Printf("deleting \"%s\"...\n", f)
			err = os.Remove(f)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

func (c *configuration) readFromFile(cfgFile string) error {
	if _, err := os.Stat(cfgFile); os.IsNotExist(err) {
		return err
	}

	file, err := os.Open(cfgFile)
	if err != nil {
		return err
	}
	defer file.Close()

	decoder := xml.NewDecoder(file)

	for {
		t, _ := decoder.Token()
		if t == nil {
			break
		}

		switch se := t.(type) {
		case xml.StartElement:
			if se.Name.Local == "config" {
				decoder.DecodeElement(c, &se)
				if err != nil {
					return err
				}
			}
		}
	}

	return nil
}