diff --git a/Makefile b/Makefile
index 28120a7..de24c25 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,9 @@
 VERSION=0.0.7
-GITCOMMIT?=$(shell git describe --dirty --always)
-LDFLAGS=-ldflags "-w -s -X main.version=${VERSION} -X main.commit=${GITCOMMIT}"
+LDFLAGS=-ldflags "-w -s -X main.version=${VERSION}"
 
 all: check-diff
 
-.PHONY: check-diff
+.PHONY: check-diff lint check linux
 
 check-diff: *.go
 	go build $(LDFLAGS) -o check-diff
diff --git a/check.go b/check.go
new file mode 100644
index 0000000..45011e3
--- /dev/null
+++ b/check.go
@@ -0,0 +1,97 @@
+package main
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/user"
+	"path/filepath"
+	"strings"
+
+	"github.com/mackerelio/checkers"
+	"github.com/monitoring-forge/saferio"
+)
+
+func (opt *Opt) cmd(file *os.File) error {
+	cmd := exec.Command(opt.Command, opt.Args...)
+	var stderr bytes.Buffer
+	cmd.Stdout = file
+	cmd.Stderr = &stderr
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+	err := cmd.Wait()
+	if err != nil {
+		return fmt.Errorf("%w - %s", err, stderr.String())
+	}
+	return nil
+}
+
+func (opt *Opt) check() *checkers.Checker {
+
+	hasher := sha256.New()
+	fmt.Fprintf(hasher, "%s\x00%s\x00%s", opt.Identifier, opt.Command, strings.Join(opt.Args, "\x00"))
+
+	curUser, err := user.Current()
+	if err != nil {
+		return checkers.Critical(err.Error())
+	}
+
+	prevFileName := fmt.Sprintf("check-diff-%s-%x", curUser.Uid, hasher.Sum(nil))
+	newFile, err := os.CreateTemp(opt.Workdir, "check-diff-")
+	if err != nil {
+		return checkers.Critical(err.Error())
+	}
+
+	defer func() {
+		_ = newFile.Close()
+		_ = os.Remove(newFile.Name())
+	}()
+
+	err = opt.cmd(newFile)
+	if err != nil {
+		return checkers.Critical(err.Error())
+	}
+
+	err = newFile.Close()
+	if err != nil {
+		return checkers.Critical(err.Error())
+	}
+
+	if !saferio.FileExists(opt.Workdir, prevFileName) {
+		err = os.Rename(newFile.Name(), filepath.Join(opt.Workdir, prevFileName))
+		if err != nil {
+			return checkers.Critical(err.Error())
+		}
+		if len(opt.Args) > 0 {
+			return checkers.Ok(fmt.Sprintf("first time execution command: '%s %s'", opt.Command, strings.Join(opt.Args, " ")))
+		}
+		return checkers.Ok(fmt.Sprintf("first time execution command: '%s'", opt.Command))
+	}
+
+	diff, err := diff(filepath.Join(opt.Workdir, prevFileName), newFile.Name())
+	if err != nil {
+		return checkers.Critical(err.Error())
+	}
+
+	err = os.Rename(newFile.Name(), filepath.Join(opt.Workdir, prevFileName))
+	if err != nil {
+		return checkers.Critical(err.Error())
+	}
+
+	if diff == "" {
+		msg, err := buildNoDifferenceMsg(filepath.Join(opt.Workdir, prevFileName))
+		if err != nil {
+			return checkers.Critical(err.Error())
+		}
+		return checkers.Ok(msg)
+	}
+
+	diffMsg := buildDiffMsg(diff)
+	if opt.Warn {
+		return checkers.Warning(diffMsg)
+	}
+	return checkers.Critical(diffMsg)
+}
diff --git a/main_test.go b/check_test.go
similarity index 92%
rename from main_test.go
rename to check_test.go
index 220f1bb..86751c0 100644
--- a/main_test.go
+++ b/check_test.go
@@ -84,10 +84,10 @@ func createTempFile(t *testing.T, content string) (*os.File, func()) {
 	}
 }
 
-func TestRun(t *testing.T) {
+func TestCheck(t *testing.T) {
 	opt, file := getCmdOpt(t, "echo", []string{"Hello, World!"})
 	defer file.Close()
-	ckr := opt.run()
+	ckr := opt.check()
 	if ckr.Status != checkers.OK {
 		t.Errorf("Expected OK status, got %v", ckr.Status)
 	}
@@ -95,8 +95,8 @@ func TestRun(t *testing.T) {
 		t.Errorf("Expected first time execution message, got %q", ckr.Message)
 	}
 
-	// Run again to check for no difference
-	ckr = opt.run()
+	// Check again to check for no difference
+	ckr = opt.check()
 	if ckr.Status != checkers.OK {
 		t.Errorf("Expected OK status, got %v", ckr.Status)
 	}
@@ -105,16 +105,16 @@ func TestRun(t *testing.T) {
 	}
 }
 
-func TestRunWithDifference(t *testing.T) {
+func TestCheckWithDifference(t *testing.T) {
 	opt, file := getCmdOpt(t, "date", []string{})
 	defer file.Close()
-	// First run to create the initial state
-	opt.run()
+	// First check to create the initial state
+	opt.check()
 
 	// Change the command to produce a different output
 	time.Sleep(2 * time.Second) // Ensure the date command produces a different output
 	opt.Command = "date"
-	ckr := opt.run()
+	ckr := opt.check()
 	if ckr.Status != checkers.CRITICAL {
 		t.Errorf("Expected CRITICAL status, got %v", ckr.Status)
 	}
diff --git a/diff.go b/diff.go
index 0422ee9..14bdba6 100644
--- a/diff.go
+++ b/diff.go
@@ -2,15 +2,17 @@ package main
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io"
 	"strings"
 
 	"github.com/cubicdaiya/gonp"
+	"github.com/monitoring-forge/saferio"
 )
 
 func getLines(filename string) ([]string, error) {
-	file, err := openRD(filename)
+	file, err := saferio.OpenRD(filename)
 	if err != nil {
 		return nil, err
 	}
@@ -29,23 +31,23 @@ func getLines(filename string) ([]string, error) {
 }
 
 func diff(prev, current string) (string, error) {
-    prevLines, err := getLines(prev)
-    if err != nil {
-        return "", err
-    }
-    newLines, err := getLines(current)
-    if err != nil {
-        return "", err
-    }
+	prevLines, err := getLines(prev)
+	if err != nil {
+		return "", err
+	}
+	newLines, err := getLines(current)
+	if err != nil {
+		return "", err
+	}
 
-    d := gonp.New(prevLines, newLines)
-    d.Compose()
+	d := gonp.New(prevLines, newLines)
+	d.Compose()
 
-    return d.SprintUniHunks(d.UnifiedHunks()), nil
+	return d.SprintUniHunks(d.UnifiedHunks()), nil
 }
 
 func buildNoDifferenceMsg(filename string) (string, error) {
-	file, err := openRD(filename)
+	file, err := saferio.OpenRD(filename)
 	if err != nil {
 		return "", err
 	}
@@ -57,7 +59,7 @@ func buildNoDifferenceMsg(filename string) (string, error) {
 	}
 	b := make([]byte, 128)
 	count, err := file.Read(b)
-	if err != nil && err != io.EOF {
+	if err != nil && !errors.Is(err, io.EOF) {
 		return "", err
 	}
 	o := string(strings.TrimRight(string(b[0:count]), "\r\n"))
diff --git a/go.mod b/go.mod
index 4493079..fe51142 100644
--- a/go.mod
+++ b/go.mod
@@ -11,5 +11,7 @@ require github.com/cubicdaiya/gonp v1.0.4
 
 require (
 	github.com/mackerelio/golib v1.2.2
+	github.com/monitoring-forge/flagrun v0.0.7
+	github.com/monitoring-forge/saferio v0.0.2
 	golang.org/x/sys v0.47.0 // indirect
 )
diff --git a/go.sum b/go.sum
index 3ff45c5..e3872e2 100644
--- a/go.sum
+++ b/go.sum
@@ -6,5 +6,9 @@ github.com/mackerelio/checkers v0.2.1 h1:vRXzAT+CEyaLjSrHVxKUBjyWq1kfo8QcI8ZoSKZ
 github.com/mackerelio/checkers v0.2.1/go.mod h1:CW3k/5bvHhxDrfKgWvMvNH0R51zco141ZVxlI7o/KAc=
 github.com/mackerelio/golib v1.2.2 h1:fQfW1o2KvPyIsAH/7+M2J0gpf2jLu+NyYpDCN79zxW4=
 github.com/mackerelio/golib v1.2.2/go.mod h1:itcSOfrsT5XvkzflFPebT43RrliaKDz2T6YGYt3jclw=
+github.com/monitoring-forge/flagrun v0.0.7 h1:6UpM8waZzN0KiZJJ2xHP64TncdmMKHE6W2HBxJwhAZA=
+github.com/monitoring-forge/flagrun v0.0.7/go.mod h1:yAwxGIEx81wU4JOMp6hz7SdSYWgT/Hr4JXEdHlEn1mw=
+github.com/monitoring-forge/saferio v0.0.2 h1:DJ4D4e7tBuMze4Ez7N7l7pGPAJ/oFsC0mwh+dg5UkwE=
+github.com/monitoring-forge/saferio v0.0.2/go.mod h1:N2nfAMrgYrax2CdwKIIWIjy5tIrlQFtJJWzKess30KY=
 golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
 golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
diff --git a/main.go b/main.go
index d13fc97..a4dfe7c 100644
--- a/main.go
+++ b/main.go
@@ -1,30 +1,14 @@
 package main
 
 import (
-	"bytes"
-	"crypto/sha256"
-	"fmt"
 	"os"
-	"os/exec"
-	"os/user"
-	"path/filepath"
-	"runtime"
-	"strings"
 
-	"github.com/jessevdk/go-flags"
 	"github.com/mackerelio/checkers"
 	"github.com/mackerelio/golib/pluginutil"
+	"github.com/monitoring-forge/flagrun"
 )
 
 var version string
-var commit string
-
-const (
-	OK = iota
-	WARNING
-	CRITICAL
-	UNKNOWN
-)
 
 type Opt struct {
 	Args       []string
@@ -35,125 +19,7 @@ type Opt struct {
 	Version    bool   `short:"v" long:"version" description:"Show version"`
 }
 
-func (opt *Opt) cmd(file *os.File) error {
-	cmd := exec.Command(opt.Command, opt.Args...)
-	var stderr bytes.Buffer
-	cmd.Stdout = file
-	cmd.Stderr = &stderr
-	if err := cmd.Start(); err != nil {
-		return err
-	}
-	err := cmd.Wait()
-	if err != nil {
-		return fmt.Errorf("%w - %s", err, stderr.String())
-	}
-	return nil
-}
-
-func (opt *Opt) run() *checkers.Checker {
-
-	identifier := strings.Join([]string{
-		opt.Identifier,
-		opt.Command,
-		strings.Join(opt.Args, "-"),
-	}, "-")
-	hasher := sha256.New()
-	hasher.Write([]byte(identifier))
-
-	curUser, err := user.Current()
-	if err != nil {
-		return checkers.Critical(err.Error())
-	}
-
-	prevPath := filepath.Join(opt.Workdir, fmt.Sprintf("check-diff-%s-%x", curUser.Uid, hasher.Sum(nil)))
-	newFile, err := os.CreateTemp(opt.Workdir, "check-diff-")
-	if err != nil {
-		return checkers.Critical(err.Error())
-	}
-
-	err = opt.cmd(newFile)
-	if err != nil {
-		newFile.Close()
-		_ = os.Remove(newFile.Name())
-		return checkers.Critical(err.Error())
-	}
-
-	err = newFile.Close()
-	if err != nil {
-		return checkers.Critical(err.Error())
-	}
-
-	if !fileExists(prevPath) {
-		err = os.Rename(newFile.Name(), prevPath)
-		if err != nil {
-			return checkers.Critical(err.Error())
-		}
-		if len(opt.Args) > 0 {
-			return checkers.Ok(fmt.Sprintf("first time execution command: '%s %s'", opt.Command, strings.Join(opt.Args, " ")))
-		}
-		return checkers.Ok(fmt.Sprintf("first time execution command: '%s'", opt.Command))
-	}
-
-	diff, err := diff(prevPath, newFile.Name())
-	if err != nil {
-		return checkers.Critical(err.Error())
-	}
-
-	err = os.Rename(newFile.Name(), prevPath)
-	if err != nil {
-		return checkers.Critical(err.Error())
-	}
-
-	if diff == "" {
-		msg, err := buildNoDifferenceMsg(prevPath)
-		if err != nil {
-			return checkers.Critical(err.Error())
-		}
-		return checkers.Ok(msg)
-	}
-
-	diffMsg := buildDiffMsg(diff)
-	if opt.Warn {
-		return checkers.Warning(diffMsg)
-	}
-	return checkers.Critical(diffMsg)
-}
-
-func fileExists(filename string) bool {
-	_, err := os.Stat(filename)
-	return err == nil
-}
-
-func main() {
-	opt := &Opt{}
-	psr := flags.NewParser(opt, flags.HelpFlag|flags.PassDoubleDash)
-	psr.Usage = "[OPTIONS] -- command args1 args2"
-	args, err := psr.Parse()
-	if opt.Version {
-		if commit == "" {
-			commit = "dev"
-		}
-		fmt.Printf(
-			"%s-%s\n%s/%s, %s, %s\n",
-			filepath.Base(os.Args[0]),
-			version,
-			runtime.GOOS,
-			runtime.GOARCH,
-			runtime.Version(),
-			commit)
-		os.Exit(OK)
-	} else if flags.WroteHelp(err) {
-		fmt.Fprintf(os.Stdout, "%v\n", err)
-		os.Exit(OK)
-	} else if err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
-		os.Exit(UNKNOWN)
-	} else if len(args) == 0 {
-		fmt.Fprintf(os.Stderr, "command is required\n")
-		psr.WriteHelp(os.Stderr)
-		os.Exit(UNKNOWN)
-	}
-
+func (opt *Opt) Run(args []string) *checkers.Checker {
 	opt.Args = []string{}
 	opt.Command = args[0]
 	if len(args) > 1 {
@@ -164,7 +30,9 @@ func main() {
 		opt.Workdir = pluginutil.PluginWorkDir()
 	}
 
-	ckr := opt.run()
-	ckr.Name = "check-diff"
-	ckr.Exit()
+	return opt.check()
+}
+
+func main() {
+	os.Exit(flagrun.Check(&Opt{}, flagrun.Version(version), flagrun.ArgsRequired()))
 }
diff --git a/open_unix.go b/open_unix.go
deleted file mode 100644
index d4ff433..0000000
--- a/open_unix.go
+++ /dev/null
@@ -1,15 +0,0 @@
-//go:build !windows
-// +build !windows
-
-package main
-
-import (
-	"os"
-	"syscall"
-)
-
-// openRD opens a file for reading with O_NOFOLLOW flag to prevent symlink attacks.
-// This function is specific to Unix-like systems where syscall.O_NOFOLLOW is available.
-func openRD(filename string) (*os.File, error) {
-	return os.OpenFile(filename, os.O_RDONLY|syscall.O_NOFOLLOW, 0)
-}
diff --git a/open_windows.go b/open_windows.go
deleted file mode 100644
index 1f6d94d..0000000
--- a/open_windows.go
+++ /dev/null
@@ -1,12 +0,0 @@
-//go:build windows
-// +build windows
-
-package main
-
-import "os"
-
-// openRD opens a file for reading with appropriate flags for Windows.
-// Since Windows doesn't support O_NOFOLLOW, we simply open the file with O_RDONLY.
-func openRD(filename string) (*os.File, error) {
-	return os.OpenFile(filename, os.O_RDONLY, 0)
-}