coreutils/ln.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini ln implementation for busybox
   4  *
   5  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9
  10 /* BB_AUDIT SUSv3 compliant */
  11 /* BB_AUDIT GNU options missing: -d, -F, -i, and -v. */
  12 /* http://www.opengroup.org/onlinepubs/007904975/utilities/ln.html */
  13
  14 #include "libbb.h"
  15
  16 /* This is a NOEXEC applet. Be very careful! */
  17
  18
  19 #define LN_SYMLINK          1
  20 #define LN_FORCE            2
  21 #define LN_NODEREFERENCE    4
  22 #define LN_BACKUP           8
  23 #define LN_SUFFIX           16
  24
  25 int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  26 int ln_main(int argc, char **argv)
  27 {
  28         int status = EXIT_SUCCESS;
  29         int opts;
  30         char *last;
  31         char *src_name;
  32         char *src;
  33         char *suffix = (char*)"~";
  34         struct stat statbuf;
  35         int (*link_func)(const char *, const char *);
  36
  37         opt_complementary = "-1"; /* min one arg */
  38         opts = getopt32(argv, "sfnbS:", &suffix);
  39
  40         last = argv[argc - 1];
  41         argv += optind;
  42
  43         if (!argv[1]) {
  44                 /* "ln PATH/TO/FILE" -> "ln PATH/TO/FILE FILE" */
  45                 *--argv = last;
  46                 /* xstrdup is needed: "ln -s PATH/TO/FILE/" is equivalent to
  47                  * "ln -s PATH/TO/FILE/ FILE", not "ln -s PATH/TO/FILE FILE"
  48                  */
  49                 last = bb_get_last_path_component_strip(xstrdup(last));
  50         }
  51
  52         do {
  53                 src_name = NULL;
  54                 src = last;
  55
  56                 if (is_directory(src,
  57                                 (opts & LN_NODEREFERENCE) ^ LN_NODEREFERENCE,
  58                                 NULL)
  59                 ) {
  60                         src_name = xstrdup(*argv);
  61                         src = concat_path_file(src, bb_get_last_path_component_strip(src_name));
  62                         free(src_name);
  63                         src_name = src;
  64                 }
  65                 if (!(opts & LN_SYMLINK) && stat(*argv, &statbuf)) {
  66                         // coreutils: "ln dangling_symlink new_hardlink" works
  67                         if (lstat(*argv, &statbuf) || !S_ISLNK(statbuf.st_mode)) {
  68                                 bb_simple_perror_msg(*argv);
  69                                 status = EXIT_FAILURE;
  70                                 free(src_name);
  71                                 continue;
  72                         }
  73                 }
  74
  75                 if (opts & LN_BACKUP) {
  76                         char *backup;
  77                         backup = xasprintf("%s%s", src, suffix);
  78                         if (rename(src, backup) < 0 && errno != ENOENT) {
  79                                 bb_simple_perror_msg(src);
  80                                 status = EXIT_FAILURE;
  81                                 free(backup);
  82                                 continue;
  83                         }
  84                         free(backup);
  85                         /*
  86                          * When the source and dest are both hard links to the same
  87                          * inode, a rename may succeed even though nothing happened.
  88                          * Therefore, always unlink().
  89                          */
  90                         unlink(src);
  91                 } else if (opts & LN_FORCE) {
  92                         unlink(src);
  93                 }
  94
  95                 link_func = link;
  96                 if (opts & LN_SYMLINK) {
  97                         link_func = symlink;
  98                 }
  99
 100                 if (link_func(*argv, src) != 0) {
 101                         bb_simple_perror_msg(src);
 102                         status = EXIT_FAILURE;
 103                 }
 104
 105                 free(src_name);
 106
 107         } while ((++argv)[1]);
 108
 109         return status;
 110 }