add no-clobber flag

cmd/katana/main.go

@@ -176,6 +176,7 @@ pipelines offering both headless and non-headless crawling.`)
 		flagSet.StringVarP(&options.OutputFile, "output", "o", "", "file to write output to"),
 		flagSet.BoolVarP(&options.StoreResponse, "store-response", "sr", false, "store http requests/responses"),
 		flagSet.StringVarP(&options.StoreResponseDir, "store-response-dir", "srd", "", "store http requests/responses to custom directory"),
+		flagSet.BoolVarP(&options.NoClobber, "no-clobber", "ncb", false, "do not overwrite output file"),
 		flagSet.BoolVarP(&options.OmitRaw, "omit-raw", "or", false, "omit raw requests/responses from jsonl output"),
 		flagSet.BoolVarP(&options.OmitBody, "omit-body", "ob", false, "omit response body from jsonl output"),
 		flagSet.BoolVarP(&options.JSON, "jsonl", "j", false, "write output in jsonl format"),

pkg/output/options.go

@@ -12,6 +12,7 @@ type Options struct {
 	JSON                  bool
 	Verbose               bool
 	StoreResponse         bool
+	NoClobber             bool
 	OmitRaw               bool
 	OmitBody              bool
 	OutputFile            string

pkg/output/output.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"strconv"
 	"strings"
 	"sync"
 
@@ -16,6 +17,7 @@ import (
 	"github.com/projectdiscovery/gologger"
 	"github.com/projectdiscovery/katana/pkg/utils/extensions"
 	errorutil "github.com/projectdiscovery/utils/errors"
+	fileutil "github.com/projectdiscovery/utils/file"
 )
 
 const (
@@ -48,6 +50,7 @@ type StandardWriter struct {
 	outputMutex           *sync.Mutex
 	storeResponse         bool
 	storeResponseDir      string
+	noClobber             bool
 	omitRaw               bool
 	omitBody              bool
 	errorFile             *fileWriter
@@ -68,6 +71,7 @@ func New(options Options) (Writer, error) {
 		outputMutex:           &sync.Mutex{},
 		storeResponse:         options.StoreResponse,
 		storeResponseDir:      options.StoreResponseDir,
+		noClobber:             options.NoClobber,
 		omitRaw:               options.OmitRaw,
 		omitBody:              options.OmitBody,
 		matchRegex:            options.MatchRegex,
@@ -117,8 +121,13 @@ func New(options Options) (Writer, error) {
 		if options.StoreResponseDir != DefaultResponseDir && options.StoreResponseDir != "" {
 			writer.storeResponseDir = options.StoreResponseDir
 		}
-		_ = os.RemoveAll(writer.storeResponseDir)
-		_ = os.MkdirAll(writer.storeResponseDir, os.ModePerm)
+		if options.NoClobber {
+			writer.storeResponseDir = createDirNameNoClobber(writer.storeResponseDir)
+			_ = os.MkdirAll(writer.storeResponseDir, os.ModePerm)
+		} else {
+			removeDirsWithSuffix(writer.storeResponseDir)
+			_ = os.MkdirAll(writer.storeResponseDir, os.ModePerm)
+		}
 		// todo: the index file seems never used?
 		_, err := newFileOutputWriter(filepath.Join(writer.storeResponseDir, indexFile))
 		if err != nil {
@@ -252,6 +261,53 @@ func (w *StandardWriter) Close() error {
 	return nil
 }
 
+func createDirNameNoClobber(dir string) string {
+	if !fileutil.FolderExists(dir) {
+		return dir
+	}
+
+	parentDir, dirName := filepath.Dir(dir), filepath.Base(dir)
+	entries, err := os.ReadDir(parentDir)
+	if err != nil {
+		return dirName
+	}
+
+	highestNum := 0
+	regex := regexp.MustCompile(fmt.Sprintf("^%s(\\d+)$", regexp.QuoteMeta(dirName)))
+	for _, entry := range entries {
+		if entry.IsDir() {
+			name := entry.Name()
+			matches := regex.FindStringSubmatch(name)
+			if matches != nil {
+				if num, err := strconv.Atoi(matches[1]); err == nil && num > highestNum {
+					highestNum = num
+				}
+			}
+		}
+	}
+
+	newDirName := fmt.Sprintf("%s%d", dirName, highestNum+1)
+	newFullPath := filepath.Join(parentDir, newDirName)
+	return newFullPath
+}
+
+func removeDirsWithSuffix(dir string) {
+	parentDir, dirName := filepath.Dir(dir), filepath.Base(dir)
+	entries, _ := os.ReadDir(parentDir)
+
+	pattern := fmt.Sprintf("^%s(\\d*)$", regexp.QuoteMeta(dirName))
+	regex := regexp.MustCompile(pattern)
+	for _, entry := range entries {
+		if entry.IsDir() {
+			name := entry.Name()
+			if regex.MatchString(name) {
+				fullPath := filepath.Join(parentDir, name)
+				_ = os.RemoveAll(fullPath)
+			}
+		}
+	}
+}
+
 // matchOutput checks if the event matches the output regex
 func (w *StandardWriter) matchOutput(event *Result) bool {
 	if w.matchRegex == nil && w.outputMatchCondition == "" {

pkg/types/crawler_options.go

@@ -72,6 +72,7 @@ func NewCrawlerOptions(options *Options) (*CrawlerOptions, error) {
 		Fields:                options.Fields,
 		StoreFields:           options.StoreFields,
 		StoreResponseDir:      options.StoreResponseDir,
+		NoClobber:             options.NoClobber,
 		OmitRaw:               options.OmitRaw,
 		OmitBody:              options.OmitBody,
 		FieldConfig:           options.FieldConfig,

pkg/types/options.go

@@ -114,6 +114,8 @@ type Options struct {
 	StoreResponse bool
 	// StoreResponseDir specifies if katana should use a custom directory to store http requests/responses
 	StoreResponseDir string
+	// NoClobber specifies if katana should overwrite existing output files
+	NoClobber bool
 	// OmitRaw omits raw requests/responses from the output
 	OmitRaw bool
 	// OmitBody omits the response body from the output