/* * Copyright (c) 2014 * The President and Fellows of Harvard College. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Create a sparse file by writing one byte to the end of it. * * Should work on emufs (emu0:) once the basic system calls are done, * and should work on SFS when the file system assignment is * done. Sufficiently small files should work on SFS even before that * assignment. */ #include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <err.h> int main(int argc, char *argv[]) { const char *filename; int size; int fd; int r; char byte; if (argc != 3) { errx(1, "Usage: sparsefile <filename> <size>"); } filename = argv[1]; size = atoi(argv[2]); byte = '\n'; if (size == 0) { err(1, "Sparse files of length zero are not meaningful"); } printf("Creating a sparse file of size %d\n", size); fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC); if (fd < 0) { err(1, "%s: create", filename); } if (lseek(fd, size-1, SEEK_SET) == -1) { err(1, "%s: lseek", filename); } r = write(fd, &byte, 1); if (r < 0) { err(1, "%s: write", filename); } else if (r != 1) { errx(1, "%s: write: Unexpected result count %d", filename, r); } close(fd); return 0; }