int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
size_t *num_bytes);
int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes);
+int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds);
int write_nonblock(int fd, const char *buf, size_t len,
size_t max_bytes_per_write);
int for_each_file_in_dir(const char *dirname,