Code Examples

Golang Listing Directory Contents and Sorting by File Name 2020-06-09

Listing the contents of a directory in go and sorting by filename.

To get the list of file we will use the ReadDir function from the os package.

To sort the files we will use the sort package to arrange the filenames alphabetically ascending or descending.

package main

import (
	"fmt"
	"io/fs"
	"log"
	"os"
	"sort"
)

func checkErr(err error) {
	if err != nil {
		log.Fatal(err)
	}
}

// this is the default sort order of golang ReadDir
func SortFileNameAscend(files []fs.DirEntry) {
	sort.Slice(files, func(i, j int) bool {
		return files[i].Name() < files[j].Name()
	})
}

func SortFileNameDescend(files []fs.DirEntry) {
	sort.Slice(files, func(i, j int) bool {
		return files[i].Name() > files[j].Name()
	})
}

func printFiles(files []fs.DirEntry) {
	for _, file := range files {
		fileInfo, err := file.Info()
		checkErr(err)
		fmt.Println(file.Name(), fileInfo.Size(), fileInfo.ModTime())
	}
}

func main() {
	files, err := os.ReadDir(".")
	if err != nil {
		log.Fatal(err)
	}

	//SortFileNameAscend(files)
	printFiles(files)

	fmt.Println("\n-----------------------------------\n")

	SortFileNameDescend(files)

	printFiles(files)
}

Golang Listing Directory Contents and Sorting by File Size 2020-06-09

Listing the contents of a directory in go and sorting by file size.

To get the list of file we will use the ReadDir function from os package.

To sort the files we will use the sort package and compare the file sizes to arrange them in ascending or descending order.

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"sort"
)

func SortFileSizeAscend(files []os.FileInfo) {
	sort.Slice(files, func(i, j int) bool {
		return files[i].Size() < files[j].Size()
	})
}

func SortFileSizeDescend(files []os.FileInfo) {
	sort.Slice(files, func(i, j int) bool {
		return files[i].Size() > files[j].Size()
	})
}

func printFiles(files []os.FileInfo) {
	for _, file := range files {
		fmt.Println(file.Name(), file.Size(), file.ModTime())
	}
}

func main() {
	files, err := ioutil.ReadDir(".")
	if err != nil {
		log.Fatal(err)
	}

	SortFileSizeAscend(files)

	printFiles(files)

	fmt.Println("\n-----------------------------------\n")

	SortFileSizeDescend(files)

	printFiles(files)
}