diff --git a/src/natives/io_lib.cpp b/src/natives/io_lib.cpp
index d7f0c8e..834491a 100644
--- a/src/natives/io_lib.cpp
+++ b/src/natives/io_lib.cpp
@@ -178,8 +178,9 @@ var builtin_stat(context* ctx, gc* ngc) {
         return nas_err("io::stat", "\"filename\" must be string");
     }
     struct stat buffer;
-    if (stat(name.str().c_str(), &buffer)<0) {
-        return nas_err("io::stat", "failed to open file <" + name.str() + ">");
+    // if failed to stat, return nil
+    if (stat(name.str().c_str(), &buffer) < 0) {
+        return nil;
     }
     auto result = ngc->alloc(vm_type::vm_vec);
     result.vec().elems = {
diff --git a/std/io.nas b/std/io.nas
index bbc9e74..2ea34e5 100644
--- a/std/io.nas
+++ b/std/io.nas
@@ -76,6 +76,9 @@ var stderr = func() { return __stderr; }();
 # get file status. using data from stat
 var fstat = func(filename) {
     var s = stat(filename);
+    if (s == nil) {
+        return nil;
+    }
     return {
         st_dev: s[0],
         st_ino: s[1],
diff --git a/std/unix.nas b/std/unix.nas
index 714f46f..c9db58b 100644
--- a/std/unix.nas
+++ b/std/unix.nas
@@ -8,11 +8,19 @@ var _S_IFDIR = 0x4000;
 var _S_IFREG = 0x8000;
 
 var isdir = func(path) {
-    return !!bits.u32_and(io.stat(path)[2], _S_IFDIR);
+    var s = io.stat(path);
+    if (s == nil) {
+        return false;
+    }
+    return !!bits.u32_and(s[2], _S_IFDIR);
 }
 
 var isfile = func(path) {
-    return !!bits.u32_and(io.stat(path)[2], _S_IFREG);
+    var s = io.stat(path);
+    if (s == nil) {
+        return false;
+    }
+    return !!bits.u32_and(s[2], _S_IFREG);
 }
 
 var opendir = func(path) {
diff --git a/tools/find_clang.nas b/tools/find_clang.nas
new file mode 100644
index 0000000..fb00d76
--- /dev/null
+++ b/tools/find_clang.nas
@@ -0,0 +1,14 @@
+use std.unix;
+use std.file;
+
+var path_vec = split(":", unix.getenv("PATH"));
+foreach (var path; path_vec) {
+    var files = file.find_all_files(path);
+    foreach (var f; files) {
+        if (f == "clang") {
+            println(path ~ "/" ~ f);
+        } elsif (find("clang-", f) == 0 and isnum(substr(f, 5, size(f)))) {
+            println(path ~ "/" ~ f);
+        }
+    }
+}
\ No newline at end of file