#include <unistd.h> /* chamadas ao sistema: defs e decls essenciais */
#include <fcntl.h> /* O_RDONLY, O_WRONLY, O_CREAT, O_* */
int open(const char *path, int oflag [, mode]);
ssize_t read(int fildes, void *buf, size_t nbyte);
int close(int fildes);
ssize_t write(int fildes, const void *buf, size_t nbyte);