coreutils/truncate.c

   1 /*
   2  * Mini truncate implementation for busybox
   3  *
   4  * Copyright (C) 2015 by Ari Sundholm <ari@tuxera.com>
   5  *
   6  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   7  */
   8 //config:config TRUNCATE
   9 //config:       bool "truncate (4.4 kb)"
  10 //config:       default y
  11 //config:       help
  12 //config:       truncate truncates files to a given size. If a file does
  13 //config:       not exist, it is created unless told otherwise.
  14
  15 //applet:IF_TRUNCATE(APPLET_NOFORK(truncate, truncate, BB_DIR_USR_BIN, BB_SUID_DROP, truncate))
  16
  17 //kbuild:lib-$(CONFIG_TRUNCATE) += truncate.o
  18
  19 //usage:#define truncate_trivial_usage
  20 //usage:       "[-c] -s SIZE FILE..."
  21 //usage:#define truncate_full_usage "\n\n"
  22 //usage:        "Truncate FILEs to SIZE\n"
  23 //usage:        "\n     -c      Do not create files"
  24 //usage:        "\n     -s SIZE"
  25 //usage:
  26 //usage:#define truncate_example_usage
  27 //usage:        "$ truncate -s 1G foo"
  28
  29 #include "libbb.h"
  30
  31 #if ENABLE_LFS
  32 # define XATOU_SFX xatoull_sfx
  33 #else
  34 # define XATOU_SFX xatoul_sfx
  35 #endif
  36
  37 /* This is a NOFORK applet. Be very careful! */
  38
  39 int truncate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  40 int truncate_main(int argc UNUSED_PARAM, char **argv)
  41 {
  42         unsigned opts;
  43         int flags = O_WRONLY | O_NONBLOCK;
  44         int ret = EXIT_SUCCESS;
  45         char *size_str;
  46         off_t size;
  47
  48         enum {
  49                 OPT_NOCREATE  = (1 << 0),
  50                 OPT_SIZE = (1 << 1),
  51         };
  52
  53         opts = getopt32(argv, "^" "cs:" "\0" "s:-1", &size_str);
  54
  55         if (!(opts & OPT_NOCREATE))
  56                 flags |= O_CREAT;
  57
  58         // TODO: coreutils 8.17 also support "m" (lowercase) suffix
  59         // with truncate, but not with dd!
  60         // We share kMG_suffixes[], so we can't make both tools
  61         // compatible at once...
  62         size = XATOU_SFX(size_str, kMG_suffixes);
  63
  64         argv += optind;
  65         while (*argv) {
  66                 int fd = open(*argv, flags, 0666);
  67                 if (fd < 0) {
  68                         if (errno != ENOENT || !(opts & OPT_NOCREATE)) {
  69                                 bb_perror_msg("%s: open", *argv);
  70                                 ret = EXIT_FAILURE;
  71                         }
  72                         /* else: ENOENT && OPT_NOCREATE:
  73                          * do not report error, exitcode is also 0.
  74                          */
  75                 } else {
  76                         if (ftruncate(fd, size) == -1) {
  77                                 bb_perror_msg("%s: truncate", *argv);
  78                                 ret = EXIT_FAILURE;
  79                         }
  80                         xclose(fd);
  81                 }
  82                 ++argv;
  83         }
  84
  85         return ret;
  86 }