ssize_t pread(int fildes, void *buf, size_t nbyte, off_t offset);
ssize_t pwrite(int fildes, const void *buf, size_t nbyte,
off_t offset);
ssize_t pread(int fildes, void *buf, size_t nbyte, off_t offset);
ssize_t pwrite(int fildes, const void *buf, size_t nbyte,
off_t offset);