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 tarball for details.
   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 "busybox.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);
  26 int ln_main(int argc, char **argv)
  27 {
  28         int status = EXIT_SUCCESS;
  29         int flag;
  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         flag = getopt32(argc, argv, "sfnbS:", &suffix);
  38
  39         if (argc == optind) {
  40                 bb_show_usage();
  41         }
  42
  43         last = argv[argc - 1];
  44         argv += optind;
  45
  46         if (argc == optind + 1) {
  47                 *--argv = last;
  48                 last = bb_get_last_path_component(xstrdup(last));
  49         }
  50
  51         do {
  52                 src_name = NULL;
  53                 src = last;
  54
  55                 if (is_directory(src,
  56                                 (flag & LN_NODEREFERENCE) ^ LN_NODEREFERENCE,
  57                                 NULL)) {
  58                         src_name = xstrdup(*argv);
  59                         src = concat_path_file(src, bb_get_last_path_component(src_name));
  60                         free(src_name);
  61                         src_name = src;
  62                 }
  63                 if (!(flag & LN_SYMLINK) && stat(*argv, &statbuf)) {
  64                         // coreutils: "ln dangling_symlink new_hardlink" works
  65                         if (lstat(*argv, &statbuf) || !S_ISLNK(statbuf.st_mode)) {
  66                                 bb_perror_msg("%s", *argv);
  67                                 status = EXIT_FAILURE;
  68                                 free(src_name);
  69                                 continue;
  70                         }
  71                 }
  72
  73                 if (flag & LN_BACKUP) {
  74                         char *backup;
  75                         backup = xasprintf("%s%s", src, suffix);
  76                         if (rename(src, backup) < 0 && errno != ENOENT) {
  77                                 bb_perror_msg("%s", src);
  78                                 status = EXIT_FAILURE;
  79                                 free(backup);
  80                                 continue;
  81                         }
  82                         free(backup);
  83                         /*
  84                          * When the source and dest are both hard links to the same
  85                          * inode, a rename may succeed even though nothing happened.
  86                          * Therefore, always unlink().
  87                          */
  88                         unlink(src);
  89                 } else if (flag & LN_FORCE) {
  90                         unlink(src);
  91                 }
  92
  93                 link_func = link;
  94                 if (flag & LN_SYMLINK) {
  95                         link_func = symlink;
  96                 }
  97
  98                 if (link_func(*argv, src) != 0) {
  99                         bb_perror_msg("%s", src);
 100                         status = EXIT_FAILURE;
 101                 }
 102
 103                 free(src_name);
 104
 105         } while ((++argv)[1]);
 106
 107         return status;
 108 }