#include <sys/stat.h> and #include <sys/types.h>
int chmod(char *path, int pmode) - Change permission settings of a file.
int fstat(int handle, struct stat *buffer) - Get file status information.
int remove(char *path) - Delete a named file.
int rename(char *oldname, char *newname) - rename a file.
int stat(char *path, struct stat *buffer) - Get file status information of named file.
unsigned umask(unsigned pmode) - Set file permission mask.