LXR busybox/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
  44int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  45int 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}
 142