diff --git a/cmd/autoupdate/npm.go b/cmd/autoupdate/npm.go
index 92499fa1..59c1f31e 100644
--- a/cmd/autoupdate/npm.go
+++ b/cmd/autoupdate/npm.go
@@ -3,8 +3,6 @@ package main
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
-	"net/http"
 	"os"
 	"path"
 	"sort"
@@ -92,7 +90,7 @@ func doUpdateNpm(ctx context.Context, pckg *packages.Package, versions []npm.Npm
 
 		util.Check(os.MkdirAll(pckgpath, os.ModePerm))
 
-		tarballDir := downloadTar(ctx, version.Tarball)
+		tarballDir := npm.DownloadTar(ctx, version.Tarball)
 		filesToCopy := pckg.NpmFilesFrom(tarballDir)
 
 		if len(filesToCopy) > 0 {
@@ -149,19 +147,3 @@ func npmVersionDiff(a []npm.NpmVersion, b []string) []npm.NpmVersion {
 
 	return diff
 }
-
-// Extract the tarball url in a temporary location
-func downloadTar(ctx context.Context, url string) string {
-	dest, err := ioutil.TempDir("", "npmtarball")
-	util.Check(err)
-
-	util.Debugf(ctx, "download %s in %s", url, dest)
-
-	resp, err := http.Get(url)
-	util.Check(err)
-
-	defer resp.Body.Close()
-
-	util.Check(npm.Untar(dest, resp.Body))
-	return dest
-}
diff --git a/cmd/checker/main.go b/cmd/checker/main.go
index d53b9ed0..69269f70 100644
--- a/cmd/checker/main.go
+++ b/cmd/checker/main.go
@@ -47,7 +47,29 @@ func main() {
 
 func showFiles(path string) {
 	ctx := util.ContextWithName(path)
-	err(ctx, "not implemented yet")
+	pckg, readerr := packages.ReadPackageJSON(ctx, path)
+	if readerr != nil {
+		err(ctx, readerr.Error())
+		return
+	}
+
+	npmVersions := npm.GetVersions(pckg.Autoupdate.Target)
+	if len(npmVersions) == 0 {
+		err(ctx, "no version found on npm")
+		return
+	}
+	lastNpmVersion := npmVersions[len(npmVersions)-1]
+	util.Printf(ctx, "%s:\n", lastNpmVersion)
+
+	tarballDir := npm.DownloadTar(ctx, lastNpmVersion.Tarball)
+	filesToCopy := pckg.NpmFilesFrom(tarballDir)
+
+	if len(filesToCopy) == 0 {
+		err(ctx, "no files to copy")
+		return
+	}
+
+	util.Printf(ctx, "%s\n", filesToCopy)
 }
 
 func lintPackage(path string) {
diff --git a/npm/tar.go b/npm/tar.go
index 90c0c9cc..1bf27847 100644
--- a/npm/tar.go
+++ b/npm/tar.go
@@ -3,10 +3,15 @@ package npm
 import (
 	"archive/tar"
 	"compress/gzip"
+	"context"
 	"io"
+	"io/ioutil"
+	"net/http"
 	"os"
 	"path"
 	"path/filepath"
+
+	"github.com/cdnjs/tools/util"
 )
 
 func removePackageDir(path string) string {
@@ -93,3 +98,19 @@ func Untar(dst string, r io.Reader) error {
 		}
 	}
 }
+
+// Extract the tarball url in a temporary location
+func DownloadTar(ctx context.Context, url string) string {
+	dest, err := ioutil.TempDir("", "npmtarball")
+	util.Check(err)
+
+	util.Debugf(ctx, "download %s in %s", url, dest)
+
+	resp, err := http.Get(url)
+	util.Check(err)
+
+	defer resp.Body.Close()
+
+	util.Check(Untar(dest, resp.Body))
+	return dest
+}
diff --git a/util/fileglob.go b/util/fileglob.go
index faf23650..8a2c391b 100644
--- a/util/fileglob.go
+++ b/util/fileglob.go
@@ -15,7 +15,7 @@ func ListFilesGlob(base string, pattern string) []string {
 		return []string{}
 	}
 
-	fmt.Println("match", pattern, "in", base)
+	// fmt.Println("match", pattern, "in", base)
 
 	cmd := exec.Command(path.Join(GetBotBasePath(), "glob", "index.js"), pattern)
 	var out bytes.Buffer