Add df command

cmd/df/df.go

@@ -0,0 +1,167 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"syscall"
+	"text/tabwriter"
+)
+
+const (
+	pathfstab  string = "/etc/fstab"
+	pathmounts string = "/proc/mounts"
+)
+
+type filesystem struct {
+	Name        string
+	Total       int64
+	Used        int64
+	UsedPercent int
+	Available   int64
+	MountedOn   string
+}
+
+func load(path string) ([]string, error) {
+	file, err := os.Open(path)
+
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	var parsed []string
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+
+		line := scanner.Text()
+		if isCommentedLine(line) == false {
+			parsed = append(parsed, line)
+		}
+
+	}
+
+	if err = scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return parsed, nil
+}
+
+func isCommentedLine(line string) bool {
+	if line[:1] == "#" {
+		return true
+	}
+	return false
+}
+
+func findMountedFs(fstab []string, mounts []string) []*filesystem {
+	filesystems := []*filesystem{}
+	for _, fs := range fstab {
+
+		toFind := parseFstabMountPointAndType(fs)
+
+		for _, m := range mounts {
+
+			if parseMountPointAndType(m) == toFind {
+				d := new(filesystem)
+				d.Name = parseFsName(m)
+				d.MountedOn = parseMountOn(m)
+				filesystems = append(filesystems, d)
+				break
+			}
+
+		}
+
+	}
+
+	return filesystems
+}
+
+func parseFstabMountPointAndType(line string) string {
+	fields := strings.Fields(line)[1:3]
+	return strings.Join(fields, " ")
+
+}
+
+func parseMountPointAndType(line string) string {
+	fields := strings.Fields(line)[1:3]
+	return strings.Join(fields, " ")
+}
+
+func parseFsName(line string) string {
+	return strings.Fields(line)[0]
+}
+
+func parseMountOn(line string) string {
+	return strings.Fields(line)[1]
+}
+
+func calcFsUsage(filesystems []*filesystem) ([]*filesystem, error) {
+	scall := syscall.Statfs_t{}
+	for _, d := range filesystems {
+
+		err := syscall.Statfs(d.MountedOn, &scall)
+		if err != nil {
+			return nil, errors.New(fmt.Sprintf("error[%s] doing syscall to filesystem for mounted point[%s]", err, d.MountedOn))
+		}
+
+		d.Total = calcTotal(scall)
+		d.Available = calcFree(scall)
+		d.Used = calcUsed(d.Total, d.Available)
+		d.UsedPercent = calcUsedPercent(d.Total, d.Used)
+
+	}
+
+	return filesystems, nil
+}
+
+func calcTotal(scall syscall.Statfs_t) int64 {
+	return (scall.Frsize * int64(scall.Blocks)) / 1024
+}
+
+func calcFree(scall syscall.Statfs_t) int64 {
+	return (scall.Frsize * int64(scall.Bfree)) / 1024
+}
+
+func calcUsed(total int64, free int64) int64 {
+	return total - free
+}
+
+func calcUsedPercent(total int64, used int64) int {
+	return int((float64(used) * 100) / float64(total))
+}
+
+func printResultCommand(filesystems []*filesystem) {
+	w := tabwriter.NewWriter(os.Stdout, 0, 0, 3, ' ', tabwriter.TabIndent)
+	fmt.Fprintln(w, "Filesystem\tSize\tUsed\tAvail\tUse%\tMounted on\t")
+	for _, p := range filesystems {
+		fmt.Fprintln(w, fmt.Sprintf(
+			"%v\t%v\t%v\t%v\t%v\t%v\t",
+			p.Name, p.Total, p.Used, p.Available, p.UsedPercent, p.MountedOn,
+		))
+	}
+	w.Flush()
+}
+
+func main() {
+	fstab, err := load(pathfstab)
+	if err != nil {
+		errors.New(fmt.Sprintf("error loading '%v': %v", pathmounts, err.Error()))
+	}
+
+	mounts, err := load(pathmounts)
+	if err != nil {
+		errors.New(fmt.Sprintf("error loading '%v': %v", pathmounts, err.Error()))
+	}
+
+	filesystems := findMountedFs(fstab, mounts)
+	filesystems, err = calcFsUsage(filesystems)
+	if err != nil {
+		errors.New(fmt.Sprintf("error calculating paths usage: %v", err.Error()))
+	}
+
+	printResultCommand(filesystems)
+}