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:     "\n        -T      2nd arg must be a DIR"
  24 //usage:     "\n        -v      Verbose"
  25 //usage:
  26 //usage:#define ln_example_usage
  27 //usage:       "$ ln -s BusyBox /tmp/ls\n"
  28 //usage:       "$ ls -l /tmp/ls\n"
  29 //usage:       "lrwxrwxrwx    1 root     root            7 Apr 12 18:39 ls -> BusyBox*\n"
  30
  31 #include "libbb.h"
  32
  33 /* This is a NOEXEC applet. Be very careful! */
  34
  35
  36 #define LN_SYMLINK          (1 << 0)
  37 #define LN_FORCE            (1 << 1)
  38 #define LN_NODEREFERENCE    (1 << 2)
  39 #define LN_BACKUP           (1 << 3)
  40 #define LN_SUFFIX           (1 << 4)
  41 #define LN_VERBOSE          (1 << 5)
  42 #define LN_LINKFILE         (1 << 6)
  43
  44 int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  45 int ln_main(int argc, char **argv)
  46 {
  47         int status = EXIT_SUCCESS;
  48         int opts;
  49         char *last;
  50         char *src_name;
  51         char *src;
  52         char *suffix = (char*)"~";
  53         struct stat statbuf;
  54         int (*link_func)(const char *, const char *);
  55
  56         opt_complementary = "-1"; /* min one arg */
  57         opts = getopt32(argv, "sfnbS:vT", &suffix);
  58
  59         last = argv[argc - 1];
  60         argv += optind;
  61         argc -= optind;
  62
  63         if ((opts & LN_LINKFILE) && argc > 2) {
  64                 bb_error_msg_and_die("-T accepts 2 args max");
  65         }
  66
  67         if (!argv[1]) {
  68                 /* "ln PATH/TO/FILE" -> "ln PATH/TO/FILE FILE" */
  69                 *--argv = last;
  70                 /* xstrdup is needed: "ln -s PATH/TO/FILE/" is equivalent to
  71                  * "ln -s PATH/TO/FILE/ FILE", not "ln -s PATH/TO/FILE FILE"
  72                  */
  73                 last = bb_get_last_path_component_strip(xstrdup(last));
  74         }
  75
  76         do {
  77                 src_name = NULL;
  78                 src = last;
  79
  80                 if (is_directory(src,
  81                                 (opts & LN_NODEREFERENCE) ^ LN_NODEREFERENCE
  82                                 )
  83                 ) {
  84                         if (opts & LN_LINKFILE) {
  85                                 bb_error_msg_and_die("'%s' is a directory", src);
  86                         }
  87                         src_name = xstrdup(*argv);
  88                         src = concat_path_file(src, bb_get_last_path_component_strip(src_name));
  89                         free(src_name);
  90                         src_name = src;
  91                 }
  92                 if (!(opts & LN_SYMLINK) && stat(*argv, &statbuf)) {
  93                         // coreutils: "ln dangling_symlink new_hardlink" works
  94                         if (lstat(*argv, &statbuf) || !S_ISLNK(statbuf.st_mode)) {
  95                                 bb_simple_perror_msg(*argv);
  96                                 status = EXIT_FAILURE;
  97                                 free(src_name);
  98                                 continue;
  99                         }
 100                 }
 101
 102                 if (opts & LN_BACKUP) {
 103                         char *backup;
 104                         backup = xasprintf("%s%s", src, suffix);
 105                         if (rename(src, backup) < 0 && errno != ENOENT) {
 106                                 bb_simple_perror_msg(src);
 107                                 status = EXIT_FAILURE;
 108                                 free(backup);
 109                                 continue;
 110                         }
 111                         free(backup);
 112                         /*
 113                          * When the source and dest are both hard links to the same
 114                          * inode, a rename may succeed even though nothing happened.
 115                          * Therefore, always unlink().
 116                          */
 117                         unlink(src);
 118                 } else if (opts & LN_FORCE) {
 119                         unlink(src);
 120                 }
 121
 122                 link_func = link;
 123                 if (opts & LN_SYMLINK) {
 124                         link_func = symlink;
 125                 }
 126
 127                 if (opts & LN_VERBOSE) {
 128                         printf("'%s' -> '%s'\n", src, *argv);
 129                 }
 130
 131                 if (link_func(*argv, src) != 0) {
 132                         bb_simple_perror_msg(src);
 133                         status = EXIT_FAILURE;
 134                 }
 135
 136                 free(src_name);
 137
 138         } while ((++argv)[1]);
 139
 140         return status;
 141 }