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 //config:config LN
  10 //config:       bool "ln (4.5 kb)"
  11 //config:       default y
  12 //config:       help
  13 //config:       ln is used to create hard or soft links between files.
  14
  15 //applet:IF_LN(APPLET_NOEXEC(ln, ln, BB_DIR_BIN, BB_SUID_DROP, ln))
  16
  17 //kbuild:lib-$(CONFIG_LN) += ln.o
  18
  19 /* BB_AUDIT SUSv3 compliant */
  20 /* BB_AUDIT GNU options missing: -d, -F, -i, and -v. */
  21 /* http://www.opengroup.org/onlinepubs/007904975/utilities/ln.html */
  22
  23 //usage:#define ln_trivial_usage
  24 //usage:       "[OPTIONS] TARGET... LINK|DIR"
  25 //usage:#define ln_full_usage "\n\n"
  26 //usage:       "Create a link LINK or DIR/TARGET to the specified TARGET(s)\n"
  27 //usage:     "\n        -s      Make symlinks instead of hardlinks"
  28 //usage:     "\n        -f      Remove existing destinations"
  29 //usage:     "\n        -n      Don't dereference symlinks - treat like normal file"
  30 //usage:     "\n        -b      Make a backup of the target (if exists) before link operation"
  31 //usage:     "\n        -S suf  Use suffix instead of ~ when making backup files"
  32 //usage:     "\n        -T      2nd arg must be a DIR"
  33 //usage:     "\n        -v      Verbose"
  34 //usage:
  35 //usage:#define ln_example_usage
  36 //usage:       "$ ln -s BusyBox /tmp/ls\n"
  37 //usage:       "$ ls -l /tmp/ls\n"
  38 //usage:       "lrwxrwxrwx    1 root     root            7 Apr 12 18:39 ls -> BusyBox*\n"
  39
  40 #include "libbb.h"
  41
  42 /* This is a NOEXEC applet. Be very careful! */
  43
  44
  45 #define LN_SYMLINK          (1 << 0)
  46 #define LN_FORCE            (1 << 1)
  47 #define LN_NODEREFERENCE    (1 << 2)
  48 #define LN_BACKUP           (1 << 3)
  49 #define LN_SUFFIX           (1 << 4)
  50 #define LN_VERBOSE          (1 << 5)
  51 #define LN_LINKFILE         (1 << 6)
  52
  53 int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  54 int ln_main(int argc, char **argv)
  55 {
  56         int status = EXIT_SUCCESS;
  57         int opts;
  58         char *last;
  59         char *src_name;
  60         char *src;
  61         char *suffix = (char*)"~";
  62         struct stat statbuf;
  63         int (*link_func)(const char *, const char *);
  64
  65         opts = getopt32(argv, "^" "sfnbS:vT" "\0" "-1", &suffix);
  66
  67         last = argv[argc - 1];
  68         argv += optind;
  69         argc -= optind;
  70
  71         if ((opts & LN_LINKFILE) && argc > 2) {
  72                 bb_error_msg_and_die("-T accepts 2 args max");
  73         }
  74
  75         if (!argv[1]) {
  76                 /* "ln PATH/TO/FILE" -> "ln PATH/TO/FILE FILE" */
  77                 *--argv = last;
  78                 /* xstrdup is needed: "ln -s PATH/TO/FILE/" is equivalent to
  79                  * "ln -s PATH/TO/FILE/ FILE", not "ln -s PATH/TO/FILE FILE"
  80                  */
  81                 last = bb_get_last_path_component_strip(xstrdup(last));
  82         }
  83
  84         do {
  85                 src_name = NULL;
  86                 src = last;
  87
  88                 if (is_directory(src,
  89                                 (opts & LN_NODEREFERENCE) ^ LN_NODEREFERENCE
  90                                 )
  91                 ) {
  92                         if (opts & LN_LINKFILE) {
  93                                 bb_error_msg_and_die("'%s' is a directory", src);
  94                         }
  95                         src_name = xstrdup(*argv);
  96                         src = concat_path_file(src, bb_get_last_path_component_strip(src_name));
  97                         free(src_name);
  98                         src_name = src;
  99                 }
 100                 if (!(opts & LN_SYMLINK) && stat(*argv, &statbuf)) {
 101                         // coreutils: "ln dangling_symlink new_hardlink" works
 102                         if (lstat(*argv, &statbuf) || !S_ISLNK(statbuf.st_mode)) {
 103                                 bb_simple_perror_msg(*argv);
 104                                 status = EXIT_FAILURE;
 105                                 free(src_name);
 106                                 continue;
 107                         }
 108                 }
 109
 110                 if (opts & LN_BACKUP) {
 111                         char *backup;
 112                         backup = xasprintf("%s%s", src, suffix);
 113                         if (rename(src, backup) < 0 && errno != ENOENT) {
 114                                 bb_simple_perror_msg(src);
 115                                 status = EXIT_FAILURE;
 116                                 free(backup);
 117                                 continue;
 118                         }
 119                         free(backup);
 120                         /*
 121                          * When the source and dest are both hard links to the same
 122                          * inode, a rename may succeed even though nothing happened.
 123                          * Therefore, always unlink().
 124                          */
 125                         unlink(src);
 126                 } else if (opts & LN_FORCE) {
 127                         unlink(src);
 128                 }
 129
 130                 link_func = link;
 131                 if (opts & LN_SYMLINK) {
 132                         link_func = symlink;
 133                 }
 134
 135                 if (opts & LN_VERBOSE) {
 136                         printf("'%s' -> '%s'\n", src, *argv);
 137                 }
 138
 139                 if (link_func(*argv, src) != 0) {
 140                         bb_simple_perror_msg(src);
 141                         status = EXIT_FAILURE;
 142                 }
 143
 144                 free(src_name);
 145         } while ((++argv)[1]);
 146
 147         return status;
 148 }