5.2.1.1.1. Open And Close System Calls
int open (
char *pathname,
int flags);
int open (
char *pathname,
int flags, mode_t mode);
int creat (
char *pathname,
mode_t mode);
int close (int fd);
O_RDONLY, O_WRONLY, O_RDWR
O_CREAT, O_EXCL, O_TRUNC, O_APPEND
O_NONBLOCK, O_SYNC