zfs: parse GUID

internal/zfs/zfs.go

@@ -1,9 +1,14 @@
 package zfs
 
 import (
+	"bufio"
 	"context"
 	"fmt"
+	"io"
+	"log"
 	"os/exec"
+	"strconv"
+	"strings"
 	"time"
 )
 
@@ -12,7 +17,7 @@ type Snapshot struct {
 	Name         string // Full dataset@snapname
 	Dataset      string
 	Creation     time.Time
-	GUID         int64
+	GUID         uint64
 }
 
 func Cmd(ctx context.Context, arg string, a ...any) ([]byte, error) {
@@ -29,3 +34,82 @@ func Cmd(ctx context.Context, arg string, a ...any) ([]byte, error) {
 	}
 	return out, err
 }
+
+func ParseSnapshots(reader io.Reader) ([]Snapshot, error) {
+	scanner := bufio.NewScanner(reader)
+
+	snaps := make([]Snapshot, 0)
+	for scanner.Scan() {
+		line := scanner.Text()
+		params := strings.Split(line, "\t") // "zroot@foo\tTIME" -> ["zroot@foo", "TIME"]
+		if len(params) != 3 {
+			continue
+		}
+		t, err := strconv.ParseInt(params[1], 10, 64)
+		if err != nil {
+			log.Fatalf("invalid time %s", params[1])
+		}
+
+		identifier := strings.Split(params[0], "@") // zroot@foo -> ["zroot", "foo"]
+
+		GUID, err := strconv.ParseUint(params[2], 10, 64)
+		if err != nil {
+			log.Fatalf("invalid GUID: %s - %s", params[2], err.Error())
+		}
+
+		snaps = append(
+			snaps,
+			Snapshot{
+				SnapshotName: identifier[1],
+				Dataset:      identifier[0],
+				Name:         params[0],
+				Creation:     time.Unix(t, 0),
+				GUID:         GUID,
+			},
+		)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("error parsing zfs-list output: %s", err.Error())
+	}
+
+	return snaps, nil
+}
+
+func Snapshots(ctx context.Context, target string) ([]Snapshot, error) {
+	cmd := exec.CommandContext(
+		ctx,
+		"zfs",
+		"list",
+		"-Hp",
+		"-o",
+		"name,creation,guid",
+		"-t",
+		"snapshot",
+		"-s",
+		"creation",
+		target,
+	)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+	defer stdout.Close()
+
+	err = cmd.Start()
+	if err != nil {
+		return nil, err
+	}
+
+	snaps, err := ParseSnapshots(stdout)
+	if err != nil {
+		return nil, err
+	}
+
+	err = cmd.Wait()
+	if err != nil {
+		return nil, err
+	}
+
+	return snaps, err
+}