diff --git a/build-aux/build-lib.sh b/build-aux/build-lib.sh
index 22caf6e9..db102336 100755
--- a/build-aux/build-lib.sh
+++ b/build-aux/build-lib.sh
@@ -86,9 +86,11 @@ $libmes_SOURCES
 lib/mes/__assert_fail.c
 lib/mes/__mes_debug.c
 lib/posix/execv.c
+lib/posix/getcwd.c
 lib/posix/getenv.c
 lib/posix/isatty.c
 lib/posix/read.c
+lib/posix/open.c
 lib/posix/setenv.c
 lib/posix/wait.c
 lib/stdio/fgetc.c
@@ -122,10 +124,10 @@ lib/linux/dup2.c
 lib/linux/execve.c
 lib/linux/fork.c
 lib/linux/fsync.c
-lib/linux/getcwd.c
+lib/linux/_getcwd.c
 lib/linux/gettimeofday.c
 lib/linux/ioctl.c
-lib/linux/open.c
+lib/linux/_open3.c
 lib/linux/_read.c
 lib/linux/time.c
 lib/linux/unlink.c
diff --git a/include/mes/lib.h b/include/mes/lib.h
index 7145dab1..63d1eba9 100644
--- a/include/mes/lib.h
+++ b/include/mes/lib.h
@@ -41,6 +41,7 @@ char * fdgets (char *s, int count, int fd);
 int fdputc (int c, int fd);
 int fdputs (char const *s, int fd);
 int fdungetc (int c, int fd);
+char * _getcwd (char *buffer, size_t size);
 int isnumber (int c, int base);
 int mes_open (char const *file_name, int flags, int mask);
 int _open2 (char const *file_name, int flags);
diff --git a/lib/linux/_getcwd.c b/lib/linux/_getcwd.c
new file mode 100644
index 00000000..55db9a02
--- /dev/null
+++ b/lib/linux/_getcwd.c
@@ -0,0 +1,32 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mes/lib-mini.h>
+#include <linux/syscall.h>
+#include <syscall.h>
+
+char *
+_getcwd (char *buffer, size_t size)
+{
+  int r = _sys_call2 (SYS_getcwd, (long) buffer, (long) size);
+  if (r >= 0)
+    return buffer;
+  return 0;
+}
diff --git a/lib/linux/_open3.c b/lib/linux/_open3.c
new file mode 100644
index 00000000..e1bf1f7b
--- /dev/null
+++ b/lib/linux/_open3.c
@@ -0,0 +1,34 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/syscall.h>
+#include <syscall.h>
+#include <mes/lib.h>
+#include <fcntl.h>
+
+int
+_open3 (char const *file_name, int flags, int mask)
+{
+  int r = _sys_call3 (SYS_open, (long) file_name, (int) flags, (int) mask);
+  __ungetc_init ();
+  if (r > 2)
+    __ungetc_clear (r);
+  return r;
+}
diff --git a/lib/linux/getcwd.c b/lib/posix/getcwd.c
similarity index 83%
rename from lib/linux/getcwd.c
rename to lib/posix/getcwd.c
index fbb67282..39dd3bf9 100644
--- a/lib/linux/getcwd.c
+++ b/lib/posix/getcwd.c
@@ -18,20 +18,9 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <linux/syscall.h>
-#include <syscall.h>
 #include <limits.h>
 #include <sys/types.h>
 
-char *
-_getcwd (char *buffer, size_t size)
-{
-  int r = _sys_call2 (SYS_getcwd, (long) buffer, (long) size);
-  if (r >= 0)
-    return buffer;
-  return 0;
-}
-
 char *
 getcwd (char *buffer, size_t size)
 {
diff --git a/lib/linux/open.c b/lib/posix/open.c
similarity index 82%
rename from lib/linux/open.c
rename to lib/posix/open.c
index 28c65739..256f2f13 100644
--- a/lib/linux/open.c
+++ b/lib/posix/open.c
@@ -18,22 +18,10 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <linux/syscall.h>
-#include <syscall.h>
 #include <mes/lib.h>
 #include <fcntl.h>
 #include <stdarg.h>
 
-int
-_open3 (char const *file_name, int flags, int mask)
-{
-  int r = _sys_call3 (SYS_open, (long) file_name, (int) flags, (int) mask);
-  __ungetc_init ();
-  if (r > 2)
-    __ungetc_clear (r);
-  return r;
-}
-
 int
 _open2 (char const *file_name, int flags)
 {
diff --git a/simple.sh b/simple.sh
index f87d0977..4c096463 100755
--- a/simple.sh
+++ b/simple.sh
@@ -169,8 +169,10 @@ $CC -g -D HAVE_CONFIG_H=1 -I include -I include/$mes_kernel/$mes_cpu\
     lib/mes/__assert_fail.c\
     lib/mes/__mes_debug.c\
     lib/posix/execv.c\
+    lib/posix/getcwd.c\
     lib/posix/getenv.c\
     lib/posix/isatty.c\
+    lib/posix/open.c\
     lib/posix/setenv.c\
     lib/posix/wait.c\
     lib/stdio/fgetc.c\
@@ -201,10 +203,10 @@ $CC -g -D HAVE_CONFIG_H=1 -I include -I include/$mes_kernel/$mes_cpu\
     lib/linux/execve.c\
     lib/linux/fork.c\
     lib/linux/fsync.c\
-    lib/linux/getcwd.c\
+    lib/linux/_getcwd.c\
     lib/linux/gettimeofday.c\
     lib/linux/ioctl.c\
-    lib/linux/open.c\
+    lib/linux/_open3.c\
     lib/linux/read.c\
     lib/linux/time.c\
     lib/linux/unlink.c\