chmod is not working inside a Docker container

main_test.go

@@ -3,6 +3,7 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	"os"
 	"os/exec"
@@ -16,6 +17,42 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func isDocker() bool {
+	if _, err := os.Stat("/.dockerenv"); err == nil {
+		return true
+	}
+
+	paths := []string{"/proc/1/cgroup", "/proc/self/cgroup"}
+	for _, path := range paths {
+		file, err := os.Open(path)
+		if err != nil {
+			continue
+		}
+
+		scanner := bufio.NewScanner(file)
+		isDocker := false
+		for scanner.Scan() {
+			if strings.Contains(scanner.Text(), "docker") || strings.Contains(scanner.Text(), "kubepods") {
+				isDocker = true
+				break
+			}
+		}
+
+		if err := scanner.Err(); err != nil {
+			_ = file.Close()
+			return false
+		}
+
+		_ = file.Close()
+
+		if isDocker {
+			return true
+		}
+	}
+
+	return false
+}
+
 func TestMain(m *testing.M) {
 	os.Exit(testscript.RunMain(m, map[string]func() int{
 		"runme": root,
@@ -33,6 +70,17 @@ func TestRunme(t *testing.T) {
 	})
 }
 
+func TestRunmeFilePermissions(t *testing.T) {
+	if isDocker() {
+		return
+	}
+
+	testscript.Run(t, testscript.Params{
+		Dir:             "testdata/permissions",
+		ContinueOnError: true,
+	})
+}
+
 func TestRunmeFlags(t *testing.T) {
 	testscript.Run(t, testscript.Params{
 		Dir:             "testdata/flags",

testdata/script/permissions.txtar → testdata/permissions/basic.txtar

@@ -1,6 +1,6 @@
 exec chmod 000 secret
 exec chmod 000 CONTRIBUTING.md
-exec runme ls --ignore-pattern=secret
+exec runme ls
 cmp stdout output.txt
 ! stderr .