extern ssize_t
pread(int fd, void *buf, size_t count, off_t offset);
extern ssize_t
pwrite(int fd, const void *buf, size_t count, off_t offset);
extern ssize_t
pread(int fd, void *buf, size_t count, off_t offset);
extern ssize_t
pwrite(int fd, const void *buf, size_t count, off_t offset);