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 //usage:#define ln_trivial_usage
  15 //usage:       "[OPTIONS] TARGET... LINK|DIR"
  16 //usage:#define ln_full_usage "\n\n"
  17 //usage:       "Create a link LINK or DIR/TARGET to the specified TARGET(s)\n"
  18 //usage:     "\n        -s      Make symlinks instead of hardlinks"
  19 //usage:     "\n        -f      Remove existing destinations"
  20 //usage:     "\n        -n      Don't dereference symlinks - treat like normal file"
  21 //usage:     "\n        -b      Make a backup of the target (if exists) before link operation"
  22 //usage:     "\n        -S suf  Use suffix instead of ~ when making backup files"
  23 //usage:
  24 //usage:#define ln_example_usage
  25 //usage:       "$ ln -s BusyBox /tmp/ls\n"
  26 //usage:       "$ ls -l /tmp/ls\n"
  27 //usage:       "lrwxrwxrwx    1 root     root            7 Apr 12 18:39 ls -> BusyBox*\n"
  28
  29 #include "libbb.h"
  30
  31 /* This is a NOEXEC applet. Be very careful! */
  32
  33
  34 #define LN_SYMLINK          1
  35 #define LN_FORCE            2
  36 #define LN_NODEREFERENCE    4
  37 #define LN_BACKUP           8
  38 #define LN_SUFFIX           16
  39
  40 int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  41 int ln_main(int argc, char **argv)
  42 {
  43         int status = EXIT_SUCCESS;
  44         int opts;
  45         char *last;
  46         char *src_name;
  47         char *src;
  48         char *suffix = (char*)"~";
  49         struct stat statbuf;
  50         int (*link_func)(const char *, const char *);
  51
  52         opt_complementary = "-1"; /* min one arg */
  53         opts = getopt32(argv, "sfnbS:", &suffix);
  54
  55         last = argv[argc - 1];
  56         argv += optind;
  57
  58         if (!argv[1]) {
  59                 /* "ln PATH/TO/FILE" -> "ln PATH/TO/FILE FILE" */
  60                 *--argv = last;
  61                 /* xstrdup is needed: "ln -s PATH/TO/FILE/" is equivalent to
  62                  * "ln -s PATH/TO/FILE/ FILE", not "ln -s PATH/TO/FILE FILE"
  63                  */
  64                 last = bb_get_last_path_component_strip(xstrdup(last));
  65         }
  66
  67         do {
  68                 src_name = NULL;
  69                 src = last;
  70
  71                 if (is_directory(src,
  72                                 (opts & LN_NODEREFERENCE) ^ LN_NODEREFERENCE,
  73                                 NULL)
  74                 ) {
  75                         src_name = xstrdup(*argv);
  76                         src = concat_path_file(src, bb_get_last_path_component_strip(src_name));
  77                         free(src_name);
  78                         src_name = src;
  79                 }
  80                 if (!(opts & LN_SYMLINK) && stat(*argv, &statbuf)) {
  81                         // coreutils: "ln dangling_symlink new_hardlink" works
  82                         if (lstat(*argv, &statbuf) || !S_ISLNK(statbuf.st_mode)) {
  83                                 bb_simple_perror_msg(*argv);
  84                                 status = EXIT_FAILURE;
  85                                 free(src_name);
  86                                 continue;
  87                         }
  88                 }
  89
  90                 if (opts & LN_BACKUP) {
  91                         char *backup;
  92                         backup = xasprintf("%s%s", src, suffix);
  93                         if (rename(src, backup) < 0 && errno != ENOENT) {
  94                                 bb_simple_perror_msg(src);
  95                                 status = EXIT_FAILURE;
  96                                 free(backup);
  97                                 continue;
  98                         }
  99                         free(backup);
 100                         /*
 101                          * When the source and dest are both hard links to the same
 102                          * inode, a rename may succeed even though nothing happened.
 103                          * Therefore, always unlink().
 104                          */
 105                         unlink(src);
 106                 } else if (opts & LN_FORCE) {
 107                         unlink(src);
 108                 }
 109
 110                 link_func = link;
 111                 if (opts & LN_SYMLINK) {
 112                         link_func = symlink;
 113                 }
 114
 115                 if (link_func(*argv, src) != 0) {
 116                         bb_simple_perror_msg(src);
 117                         status = EXIT_FAILURE;
 118                 }
 119
 120                 free(src_name);
 121
 122         } while ((++argv)[1]);
 123
 124         return status;
 125 }