example of calculating quota of a directory, given a known maxiumum size

fs.go

package main

import (
	"fmt"
	"os"
	"path/filepath"
)

//
const (
	PartitionSize = 1024 * 1024 * 1024 * 2
	RootPath      = "/tmp/test/"
)

func min(a, b int64) int64 {
	if a > b {
		return b
	}
	return a
}

func calculate(usedSize, availSize, totalSize int64) int64 {
	return min(totalSize, availSize) - usedSize
}

func getDirUsage(root string) int64 {
	var size int64
	var err error
	err = filepath.Walk(root, func(path string, info os.FileInfo, e error) error {

		if e != nil {
			fmt.Printf("Error: %v\n", e)
			return e
		}

		/*
		   fmt.Printf("Path: %s\n", path)
		   fmt.Printf("\tName: %s\n", info.Name())
		   fmt.Printf("\tSize: %d\n", info.Size())
		   fmt.Printf("\tMode: %d\n", info.Mode())
		   fmt.Printf("\tModTime: %v\n", info.ModTime())
		   fmt.Printf("\tIsDir: %v\n", info.IsDir())
		   fmt.Printf("\tSys: %v\n\n", info.Sys())
		*/

		if info.Mode().IsRegular() {
			size = size + info.Size()
		}

		return nil
	})

	if err != nil {
		fmt.Printf("Error: %v\n", err)
	}

	return size
}

func main() {
	fmt.Printf("Calculating %s\n", RootPath)
	used := getDirUsage(RootPath)
	avail := PartitionSize - used
	quota := calculate(used, avail, PartitionSize)
	fmt.Printf("Size: %d, Used: %d, Available Size: %d, quota: %d\n", PartitionSize, used, avail, quota)
}