diff --git a/include/fcntl.h b/include/fcntl.h
index d251f65..57fe5e0 100644
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -29,6 +29,12 @@ extern int creat(char const *__path, mode_t __mode);
 /* Open file and return a file descriptor, -1 on error. */
 extern int open(char const *__path, int __flags, ... /* mode_t __mode */);
 
+#define F_DUPFD        0
+#define F_GETFD        1
+#define F_SETFD        2
+
+extern int fcntl(int fd, int op, ...);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/sys/stat.h b/include/sys/stat.h
index fc2ca0a..2cbe226 100644
--- a/include/sys/stat.h
+++ b/include/sys/stat.h
@@ -77,6 +77,8 @@ extern int stat(char const * __restrict__ __pathname,
 
 extern int chmod(char const *__pathname, mode_t mode);
 
+extern int fstat(int __fd, struct stat *__buf);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/unistd.h b/include/unistd.h
index 886fa4f..6926615 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -45,6 +45,10 @@ extern char *getcwd(char *__buf, size_t __size);
 
 extern int chdir(char const *__path);
 
+extern int isatty(int __fd);
+
+extern int dup(int __fd);
+
 /* Exit immediately, bypassing exit handlers or signal handlers. */
 __attribute__((noreturn))
 extern void _exit(int __status);
@@ -52,8 +56,6 @@ extern void _exit(int __status);
 
 /* Kernel-style functions supported only by Vhex. */
 
-#ifdef __SUPPORT_VHEX_KERNEL
-
 //---
 // Process part
 ///---
@@ -86,8 +88,6 @@ extern int setpgid(pid_t __pid, pid_t __pgid);
 /* Get the value of the system variable NAME. */
 extern long int sysconf(int __name);
 
-#endif /*__SUPPORT_VHEX_KERNEL*/
-
 #ifdef __cplusplus
 }
 #endif