diff --git a/internal/api/runner/judge.go b/internal/api/runner/judge.go
index fe33486..09242e4 100644
--- a/internal/api/runner/judge.go
+++ b/internal/api/runner/judge.go
@@ -7,6 +7,7 @@ import (
 	"git.0x7f.app/WOJ/woj-server/internal/e"
 	"git.0x7f.app/WOJ/woj-server/internal/model"
 	"git.0x7f.app/WOJ/woj-server/internal/service/runner"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"git.0x7f.app/WOJ/woj-server/pkg/utils"
 	"github.com/hibiken/asynq"
 	"go.uber.org/zap"
@@ -28,10 +29,10 @@ func (h *handler) Judge(_ context.Context, t *asynq.Task) error {
 
 		// 1. write user code
 		userCode := filepath.Join(runner.UserDir, user, fmt.Sprintf("%s.%s", user, p.Submission.Language))
-		if !utils.FileTouch(userCode) {
+		if !file.FileTouch(userCode) {
 			return e.InternalError, 0, systemError
 		}
-		err := utils.FileWrite(userCode, []byte(p.Submission.Code))
+		err := file.FileWrite(userCode, []byte(p.Submission.Code))
 		if err != nil {
 			return e.InternalError, 0, systemError
 		}
diff --git a/internal/misc/config/conf.go b/internal/misc/config/conf.go
index d213782..ca3adf2 100644
--- a/internal/misc/config/conf.go
+++ b/internal/misc/config/conf.go
@@ -2,7 +2,7 @@ package config
 
 import (
 	"git.0x7f.app/WOJ/woj-server/internal/model"
-	"git.0x7f.app/WOJ/woj-server/pkg/utils"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"github.com/samber/do"
 	"github.com/urfave/cli/v2"
 	"gopkg.in/yaml.v3"
@@ -19,7 +19,7 @@ type Service interface {
 func NewService(i *do.Injector) (Service, error) {
 	cliCtx := do.MustInvoke[*cli.Context](i)
 
-	data, err := utils.FileRead(cliCtx.String("config"))
+	data, err := file.FileRead(cliCtx.String("config"))
 	if err != nil {
 		log.Printf("Failed to setup config: %s\n", err.Error())
 		return nil, err
diff --git a/internal/service/runner/common.go b/internal/service/runner/common.go
index 138f537..b0de8c3 100644
--- a/internal/service/runner/common.go
+++ b/internal/service/runner/common.go
@@ -3,7 +3,7 @@ package runner
 import (
 	"fmt"
 	"git.0x7f.app/WOJ/woj-server/internal/e"
-	"git.0x7f.app/WOJ/woj-server/pkg/utils"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"go.uber.org/zap"
 	"os"
 	"os/exec"
@@ -69,10 +69,10 @@ func (s *service) checkAndExecute(version uint, user string, lang string, script
 
 func (s *service) ProblemExists(version uint) bool {
 	problemPath := filepath.Join(ProblemDir, fmt.Sprintf("%d", version))
-	return utils.FileExist(problemPath)
+	return file.FileExist(problemPath)
 }
 
-func (s *service) userExists(user string, file string) bool {
-	userPath := filepath.Join(UserDir, user, file)
-	return utils.FileExist(userPath)
+func (s *service) userExists(user string, name string) bool {
+	userPath := filepath.Join(UserDir, user, name)
+	return file.FileExist(userPath)
 }
diff --git a/internal/service/runner/compile.go b/internal/service/runner/compile.go
index bc129f3..ce2699b 100644
--- a/internal/service/runner/compile.go
+++ b/internal/service/runner/compile.go
@@ -3,6 +3,7 @@ package runner
 import (
 	"fmt"
 	"git.0x7f.app/WOJ/woj-server/internal/e"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"git.0x7f.app/WOJ/woj-server/pkg/utils"
 	"os"
 	"path/filepath"
@@ -15,11 +16,11 @@ func (s *service) Compile(version uint, user string, lang string) (JudgeStatus,
 	status := s.checkAndExecute(version, user, lang, "problem_compile.sh", e.RunnerUserCompileFailed)
 
 	log := filepath.Join(UserDir, user, fmt.Sprintf("%s.compile.log", user))
-	msg, err := utils.FileRead(log)
+	msg, err := file.FileRead(log)
 	msg = utils.If(err == nil, msg, nil)
 	msgText := string(msg)
 
-	if !utils.FileExist(target) || utils.FileEmpty(target) {
+	if !file.FileExist(target) || file.FileEmpty(target) {
 		return JudgeStatus{
 				Message: "compile failed",
 				Tasks:   []TaskStatus{{Verdict: VerdictCompileError, Message: msgText}}},
diff --git a/internal/service/runner/deps.go b/internal/service/runner/deps.go
index d0f8d6e..d798b4c 100644
--- a/internal/service/runner/deps.go
+++ b/internal/service/runner/deps.go
@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"git.0x7f.app/WOJ/woj-server/internal/e"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"git.0x7f.app/WOJ/woj-server/pkg/utils"
 	"go.uber.org/zap"
 	"os"
@@ -20,7 +21,7 @@ func (s *service) loadImage(cfg *depConfig) e.Status {
 	err := utils.NewTryErr().
 		Try(func() error {
 			// import from tarball
-			if !utils.FileExist(cfg.tarball) {
+			if !file.FileExist(cfg.tarball) {
 				return errors.New("tarball not exists")
 			}
 			return s.execute("bash", "-c", fmt.Sprintf("gzip -d -c %s | podman load", cfg.tarball))
@@ -31,7 +32,7 @@ func (s *service) loadImage(cfg *depConfig) e.Status {
 		}).
 		Or(func() error {
 			// build from dockerfile
-			if !utils.FileExist(cfg.dockerfile) {
+			if !file.FileExist(cfg.dockerfile) {
 				return errors.New("dockerfile not exists")
 			}
 			return s.execute("podman", "build", "-f", cfg.dockerfile, "-t", cfg.image, ".")
@@ -52,7 +53,7 @@ func (s *service) EnsureDeps(force bool) e.Status {
 	// check mark
 	if force {
 		_ = os.Remove(mark)
-	} else if utils.FileExist(mark) {
+	} else if file.FileExist(mark) {
 		return e.Success
 	}
 
diff --git a/internal/service/runner/newProblem.go b/internal/service/runner/new_problem.go
similarity index 96%
rename from internal/service/runner/newProblem.go
rename to internal/service/runner/new_problem.go
index d723604..f4b025e 100644
--- a/internal/service/runner/newProblem.go
+++ b/internal/service/runner/new_problem.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"git.0x7f.app/WOJ/woj-server/internal/e"
 	"git.0x7f.app/WOJ/woj-server/pkg/down"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"git.0x7f.app/WOJ/woj-server/pkg/unzip"
 	"git.0x7f.app/WOJ/woj-server/pkg/utils"
 	"go.uber.org/zap"
@@ -38,7 +39,7 @@ func (s *service) prebuild(version uint, force bool) e.Status {
 	mark := filepath.Join(ProblemDir, fmt.Sprintf("%d", version), ".mark.prebuild")
 	if force {
 		_ = os.Remove(mark)
-	} else if utils.FileExist(mark) {
+	} else if file.FileExist(mark) {
 		return e.Success
 	}
 
diff --git a/internal/service/runner/status.go b/internal/service/runner/status.go
index cf0bdac..c751792 100644
--- a/internal/service/runner/status.go
+++ b/internal/service/runner/status.go
@@ -5,7 +5,7 @@ import (
 	"encoding/json"
 	"encoding/xml"
 	"fmt"
-	"git.0x7f.app/WOJ/woj-server/pkg/utils"
+	"git.0x7f.app/WOJ/woj-server/pkg/file"
 	"golang.org/x/text/encoding/charmap"
 	"io"
 	"path/filepath"
@@ -57,7 +57,7 @@ func (t *TaskStatus) getInfoText(infoFile string) *TaskStatus {
 	}
 
 	var err error
-	t.infoText, err = utils.FileRead(infoFile)
+	t.infoText, err = file.FileRead(infoFile)
 	if err != nil {
 		t.Verdict = VerdictSystemError
 		t.Message = "cannot read info file"
@@ -128,7 +128,7 @@ func (t *TaskStatus) getJudgeText(judgeFile string) *TaskStatus {
 		return t
 	}
 
-	j, err := utils.FileRead(judgeFile)
+	j, err := file.FileRead(judgeFile)
 	if err != nil {
 		t.Verdict = VerdictSystemError
 		t.Message = "cannot read judge file"
diff --git a/pkg/utils/file.go b/pkg/file/file.go
similarity index 80%
rename from pkg/utils/file.go
rename to pkg/file/file.go
index a96076d..d0ad4a6 100644
--- a/pkg/utils/file.go
+++ b/pkg/file/file.go
@@ -1,6 +1,7 @@
-package utils
+package file
 
 import (
+	"git.0x7f.app/WOJ/woj-server/pkg/utils"
 	"io"
 	"os"
 	"path/filepath"
@@ -20,7 +21,7 @@ func FileWrite(filePath string, content []byte) error {
 
 func FileExist(filePath string) bool {
 	_, err := os.Stat(filePath)
-	return If(err == nil || os.IsExist(err), true, false)
+	return utils.If(err == nil || os.IsExist(err), true, false)
 }
 
 func FileEmpty(filePath string) bool {
@@ -35,5 +36,5 @@ func FileTouch(filePath string) bool {
 	base := filepath.Dir(filePath)
 	_ = os.MkdirAll(base, 0755)
 	_, err := os.OpenFile(filePath, os.O_RDONLY|os.O_CREATE, 0644)
-	return If(err == nil, true, false)
+	return utils.If(err == nil, true, false)
 }
diff --git a/pkg/file/writer.go b/pkg/file/writer.go
new file mode 100644
index 0000000..797661a
--- /dev/null
+++ b/pkg/file/writer.go
@@ -0,0 +1,21 @@
+package file
+
+import (
+	"fmt"
+	"os"
+)
+
+type LimitedWriter struct {
+	File  *os.File
+	Limit int64
+	n     int64
+}
+
+func (lw *LimitedWriter) Write(p []byte) (n int, err error) {
+	if lw.n+int64(len(p)) > lw.Limit {
+		return 0, fmt.Errorf("output limit exceeded")
+	}
+	n, err = lw.File.Write(p)
+	lw.n += int64(n)
+	return
+}