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//config:config LN
  10//config:       bool "ln (4.9 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
  53int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  54int 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}
 149