diff --git a/src/private_at_functions.c b/src/private_at_functions.c
new file mode 100644
index 0000000..3eaea21
--- /dev/null
+++ b/src/private_at_functions.c
@@ -0,0 +1,131 @@
+
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <stdio.h>
+
+#include "private_at_functions.h"
+
+
+/**************************************************************************
+ *
+ * D E C L A R A T I O N   O F   T H E   P R I V A T E   F U N C T I O N S
+ *
+ **************************************************************************/
+
+
+/**
+ * Internal function getting the full path of a file or a directory from its
+ * path relative to a directory file descriptor.
+ *
+ *
+ * @warning The returned pointer has to be freed by the caller.
+ *
+ * @param directory_file_descriptor the file descriptor for the directory to which
+ * 									path_name is relative
+ * @param path_name the path name for the file or directory, relative to directory_file_descriptor
+ *
+ * @return a pointer to the full path
+ * @retvalue <full_path> if everything is ok
+ * @retvalue NULL if an error occurs
+ *
+ * ###Error values
+ * 		- OBIDMS_MEMORY_ERROR    : something wrong occurred during memory allocation.
+ * 		- OBIDMS_LONG_NAME_ERROR : the database name exceeds the limit.
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+static char* get_full_path(int directory_file_descriptor, const char* path_name);
+
+
+/************************************************************************
+ *
+ * D E F I N I T I O N   O F   T H E   P R I V A T E   F U N C T I O N S
+ *
+ ************************************************************************/
+
+
+static char* get_full_path(int directory_file_descriptor, const char* path_name)
+{
+	char full_path[MAX_PATH_LEN];
+
+	if (fcntl(directory_file_descriptor, F_GETPATH, full_path) < 0)
+		return NULL;
+
+	if (strlcat(full_path, "/", MAX_PATH_LEN) >= sizeof(full_path))
+		return NULL;
+
+	if (strlcat(full_path, path_name, MAX_PATH_LEN) >= sizeof(full_path))
+		return NULL;
+
+	return full_path;
+}
+
+
+/**********************************************************************
+ *
+ * D E F I N I T I O N   O F   T H E   P U B L I C   F U N C T I O N S
+ *
+ **********************************************************************/
+
+
+int private_openat(int directory_file_descriptor, const char* path_name, int flags)
+{
+	int file_descriptor;
+	char full_path[MAX_PATH_LEN];
+
+	full_path = get_full_path(directory_file_descriptor, path_name);
+	if (full_path == NULL)
+		return -1;
+
+	file_descriptor = open(full_path, flags);
+
+	return file_descriptor;
+}
+
+
+int private_mkdirat(int directory_file_descriptor, const char* path_name, mode_t mode)
+{
+	int file_descriptor;
+	char full_path[MAX_PATH_LEN];
+
+	full_path = get_full_path(directory_file_descriptor, path_name);
+	if (full_path == NULL)
+		return -1;
+
+	file_descriptor = mkdir(full_path, mode);
+
+	return file_descriptor;
+}
+
+
+int private_opendirat(int directory_file_descriptor, const char* path_name)
+{
+	int file_descriptor;
+	char full_path[MAX_PATH_LEN];
+
+	full_path = get_full_path(directory_file_descriptor, path_name);
+	if (full_path == NULL)
+		return -1;
+
+	file_descriptor = opendir(full_path);
+
+	return file_descriptor;
+}
+
+
+int private_closedirat(int directory_file_descriptor, const char* path_name)
+{
+	int file_descriptor;
+	char full_path[MAX_PATH_LEN];
+
+	full_path = get_full_path(directory_file_descriptor, path_name);
+	if (full_path == NULL)
+		return -1;
+
+	file_descriptor = closedir(full_path);
+
+	return file_descriptor;
+}
diff --git a/src/private_at_functions.h b/src/private_at_functions.h
new file mode 100644
index 0000000..98eb45f
--- /dev/null
+++ b/src/private_at_functions.h
@@ -0,0 +1,76 @@
+/**
+ * @file private_openat.h
+ * @author Celine Mercier
+ * @date 15 June 2015
+ * @brief Header file for a replacement function for openat.
+ */
+
+#ifndef PRIVATE_OPENAT_H_
+#define PRIVATE_OPENAT_H_
+
+
+#include <sys/stat.h>
+
+
+#define MAX_PATH_LEN 4096
+
+
+/**
+ * @brief Replacement function for openat() : open a file relative to a directory file descriptor.
+ *
+ * @param directory_file_descriptor the file descriptor for the directory in which the file should be opened
+ * @param path_name the path name for the file, relative to directory_file_descriptor
+ * @param flags the access modes
+ *
+ * @return the file descriptor of the opened file
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+int private_openat(int directory_file_descriptor, const char* path_name, int flags);
+
+
+/**
+ * @brief Replacement function for mkdirat() : create a directory relative to a directory file descriptor.
+ *
+ * @param directory_file_descriptor the file descriptor for the directory in which the directory should be created
+ * @param path_name the path name for the new directory, relative to directory_file_descriptor
+ * @param mode the access mode
+ *
+ * @return the file descriptor of the created directory
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+int private_mkdirat(int directory_file_descriptor, const char* path_name, mode_t mode);
+
+
+/**
+ * @brief Replacement function for opendirat() : open a directory relative to a directory file descriptor.
+ *
+ * @param directory_file_descriptor the file descriptor for the directory in which the directory should be opened
+ * @param path_name the path name for the directory to be opened, relative to directory_file_descriptor
+ *
+ * @return the file descriptor of the opened directory
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+int private_opendirat(int directory_file_descriptor, const char* path_name);
+
+
+/**
+ * @brief Replacement function for closedirat() : close a directory relative to a directory file descriptor.
+ *
+ * @param directory_file_descriptor the file descriptor for the directory in which the directory should be closed
+ * @param path_name the path name for the directory to be closed, relative to directory_file_descriptor
+ *
+ * @return 0 on success and -1 on error
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+int private_closedirat(int directory_file_descriptor, const char* path_name);
+
+
+#endif /* PRIVATEOPENAT_H_ */