diff --git a/_demo/fcntl/fcntl.go b/_demo/fcntl/fcntl.go
index 11b7918c..b53686e5 100644
--- a/_demo/fcntl/fcntl.go
+++ b/_demo/fcntl/fcntl.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"github.com/goplus/llgo/c"
-	"github.com/goplus/llgo/c/fcntl"
 	"github.com/goplus/llgo/c/os"
 	"unsafe"
 )
@@ -10,12 +9,11 @@ import (
 func main() {
 
 	filename := c.Str("testfile.txt")
-	data := c.Str("Hello, fcntl!")
-
+	data := c.Str("Hello, os!")
 	var buffer [20]c.Char
 
 	// Open a file, O_CREAT|O_WRONLY|O_TRUNC means create, write only, or clear the file
-	fd := fcntl.Open(filename, fcntl.O_CREAT|fcntl.O_WRONLY|fcntl.O_TRUNC, 0644)
+	fd := os.Open(filename, os.O_CREAT|os.O_WRONLY|os.O_TRUNC, 0644)
 	if fd == -1 {
 		c.Printf(c.Str("open error\n"))
 		return
@@ -31,28 +29,30 @@ func main() {
 	c.Printf(c.Str("Written %ld bytes to %s\n"), bytesWritten, filename)
 
 	// Get file status flags
-	flags := fcntl.FcNtl(fd, fcntl.F_GETFL)
+	flags := os.Fcntl(fd, os.F_GETFL)
 	if flags == -1 {
-		c.Printf(c.Str("fcntl error\n"))
+		c.Printf(c.Str("os error\n"))
 		os.Close(fd)
 		return
 	}
 	c.Printf(c.Str("File flags: %d\n"), flags)
 
 	// Set the file status flag to non-blocking mode
-	if fcntl.FcNtl(fd, fcntl.F_SETFL, flags|fcntl.O_NONBLOCK) == -1 {
-		c.Printf(c.Str("fcntl error\n"))
+	if os.Fcntl(fd, os.F_SETFL, flags|os.O_NONBLOCK) == -1 {
+		c.Printf(c.Str("os error\n"))
 		os.Close(fd)
 		return
 	}
 	c.Printf(c.Str("set file status successfully\n"))
 
+
+
 	c.Printf(c.Str("111"))
 	// Close file
 	os.Close(fd)
 
 	// Reopen the file, O_RDONLY means read-only
-	fd = fcntl.Open(filename, fcntl.O_RDONLY)
+	fd = os.Open(filename, os.O_RDONLY)
 	if fd == -1 {
 		c.Printf(c.Str("open error\n"))
 		return
diff --git a/_demo/fcntl/testfile.txt b/_demo/fcntl/testfile.txt
deleted file mode 100644
index 48858db3..00000000
--- a/_demo/fcntl/testfile.txt
+++ /dev/null
@@ -1 +0,0 @@
-Hello, fcntl!
\ No newline at end of file
diff --git a/c/fcntl/fcntl.go b/c/fcntl/fcntl.go
deleted file mode 100644
index 2c31b8e1..00000000
--- a/c/fcntl/fcntl.go
+++ /dev/null
@@ -1,42 +0,0 @@
-package fcntl
-
-import (
-	_ "unsafe"
-
-	"github.com/goplus/llgo/c"
-)
-
-// #include <fdntl.h>
-
-const (
-	LLGoPackage = "decl"
-)
-
-const (
-	/* get file status flags */
-	F_GETFL = 3
-	/* set file status flags */
-	F_SETFL = 4
-
-	/* open for reading only */
-	O_RDONLY = 0x0000
-	/* open for writing only */
-	O_WRONLY = 0x0001
-	/* open for reading and writing */
-	O_RDWR = 0x0002
-	/* mask for above modes */
-	O_ACCMODE = 0x0003
-
-	/* no delay */
-	O_NONBLOCK = 0x00000004
-	/* create if nonexistant */
-	O_CREAT = 0x00000200
-	/* truncate to zero length */
-	O_TRUNC = 0x00000400
-)
-
-//go:linkname FcNtl C.fcntl
-func FcNtl(a c.Int, b c.Int, vars ...any) c.Int
-
-//go:linkname Open C.open
-func Open(path *c.Char, op c.Int, vars ...any) c.Int
diff --git a/c/os/os.go b/c/os/os.go
index 04ce435b..583cf631 100644
--- a/c/os/os.go
+++ b/c/os/os.go
@@ -35,6 +35,29 @@ const (
 	PATH_MAX = C.PATH_MAX
 )
 
+const (
+	/* get file status flags */
+	F_GETFL = 3
+	/* set file status flags */
+	F_SETFL = 4
+
+	/* open for reading only */
+	O_RDONLY = 0x0000
+	/* open for writing only */
+	O_WRONLY = 0x0001
+	/* open for reading and writing */
+	O_RDWR = 0x0002
+	/* mask for above modes */
+	O_ACCMODE = 0x0003
+
+	/* no delay */
+	O_NONBLOCK = 0x00000004
+	/* create if nonexistant */
+	O_CREAT = 0x00000200
+	/* truncate to zero length */
+	O_TRUNC = 0x00000400
+)
+
 type (
 	ModeT C.mode_t
 	UidT  C.uid_t
@@ -146,7 +169,7 @@ func Fstatat(dirfd c.Int, path *c.Char, buf *StatT, flags c.Int) c.Int
 // -----------------------------------------------------------------------------
 
 //go:linkname Open C.open
-func Open(path *c.Char, flags c.Int, mode ModeT) c.Int
+func Open(path *c.Char, flags c.Int, __llgo_va_list ...any) c.Int
 
 //go:linkname Openat C.openat
 func Openat(dirfd c.Int, path *c.Char, flags c.Int, mode ModeT) c.Int
@@ -154,6 +177,9 @@ func Openat(dirfd c.Int, path *c.Char, flags c.Int, mode ModeT) c.Int
 //go:linkname Creat C.creat
 func Creat(path *c.Char, mode ModeT) c.Int
 
+//go:linkname Fcntl C.fcntl
+func Fcntl(a c.Int, b c.Int, __llgo_va_list ...any) c.Int
+
 //go:linkname Dup C.dup
 func Dup(fd c.Int) c.Int