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-$(CONFIG_LN) += ln.o
18
19 /* BB_AUDIT SUSv3 compliant */
20 /* BB_AUDIT GNU options missing: -d, -F, -i, and -v. */
21 /* http://www.opengroup.org/onlinepubs/007904975/utilities/ln.html */
22
23 //usage:#define ln_trivial_usage
24 //usage: "[-sfnbtv] [-S SUF] TARGET... LINK|DIR"
25 //usage:#define ln_full_usage "\n\n"
26 //usage: "Create a link LINK or DIR/TARGET to the specified TARGET(s)\n"
27 //usage: "\n -s Make symlinks instead of hardlinks"
28 //usage: "\n -f Remove existing destinations"
29 //usage: "\n -n Don't dereference symlinks - treat like normal file"
30 //usage: "\n -b Make a backup of the target (if exists) before link operation"
31 //usage: "\n -S SUF Use suffix instead of ~ when making backup files"
32 //usage: "\n -T Treat LINK as a file, not DIR"
33 //usage: "\n -v Verbose"
34 //usage:
35 //usage:#define ln_example_usage
36 //usage: "$ 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 #define LN_SYMLINK (1 << 0)
45 #define LN_FORCE (1 << 1)
46 #define LN_NODEREFERENCE (1 << 2)
47 #define LN_BACKUP (1 << 3)
48 #define LN_SUFFIX (1 << 4)
49 #define LN_VERBOSE (1 << 5)
50 #define LN_LINKFILE (1 << 6)
51
52 int ln_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
ln_main(int argc,char ** argv)53 int ln_main(int argc, char **argv)
54 {
55 int status = EXIT_SUCCESS;
56 int opts;
57 char *last;
58 char *src_name;
59 char *src;
60 char *suffix = (char*)"~";
61 struct stat statbuf;
62 int (*link_func)(const char *, const char *);
63
64 opts = getopt32(argv, "^" "sfnbS:vT" "\0" "-1", &suffix);
65 /*
66 -s, --symbolic make symbolic links instead of hard links
67 -f, --force remove existing destination files
68 -n, --no-dereference treat LINK_NAME as a normal file if it is a symbolic link to a directory
69 -b like --backup but does not accept an argument
70 --backup[=CONTROL] make a backup of each existing destination file
71 -S, --suffix=SUFFIX override the usual backup suffix
72 -v, --verbose
73 -T, --no-target-directory
74 -d, -F, --directory allow the superuser to attempt to hard link directories
75 -i, --interactive prompt whether to remove destinations
76 -L, --logical dereference TARGETs that are symbolic links
77 -P, --physical make hard links directly to symbolic links
78 -r, --relative create symbolic links relative to link location
79 -t, --target-directory=DIRECTORY specify the DIRECTORY in which to create the links
80 */
81 last = argv[argc - 1];
82 argv += optind;
83 argc -= optind;
84
85 if ((opts & LN_LINKFILE) && argc > 2) {
86 bb_simple_error_msg_and_die("-T accepts 2 args max");
87 }
88
89 if (!argv[1]) {
90 /* "ln PATH/TO/FILE" -> "ln PATH/TO/FILE FILE" */
91 *--argv = last;
92 /* xstrdup is needed: "ln -s PATH/TO/FILE/" is equivalent to
93 * "ln -s PATH/TO/FILE/ FILE", not "ln -s PATH/TO/FILE FILE"
94 */
95 last = bb_get_last_path_component_strip(xstrdup(last));
96 }
97
98 do {
99 src_name = NULL;
100 src = last;
101
102 if (is_directory(src,
103 /*followlinks:*/ !(opts & (LN_NODEREFERENCE|LN_LINKFILE))
104 /* Why LN_LINKFILE does not follow links:
105 * -T/--no-target-directory implies -n/--no-dereference
106 */
107 )
108 ) {
109 if (opts & LN_LINKFILE) {
110 bb_error_msg_and_die("'%s' is a directory", src);
111 }
112 src_name = xstrdup(*argv);
113 src = concat_path_file(src, bb_get_last_path_component_strip(src_name));
114 free(src_name);
115 src_name = src;
116 }
117 if (!(opts & LN_SYMLINK) && stat(*argv, &statbuf)) {
118 // coreutils: "ln dangling_symlink new_hardlink" works
119 if (lstat(*argv, &statbuf) || !S_ISLNK(statbuf.st_mode)) {
120 bb_simple_perror_msg(*argv);
121 status = EXIT_FAILURE;
122 free(src_name);
123 continue;
124 }
125 }
126
127 if (opts & LN_BACKUP) {
128 char *backup;
129 backup = xasprintf("%s%s", src, suffix);
130 if (rename(src, backup) < 0 && errno != ENOENT) {
131 bb_simple_perror_msg(src);
132 status = EXIT_FAILURE;
133 free(backup);
134 continue;
135 }
136 free(backup);
137 /*
138 * When the source and dest are both hard links to the same
139 * inode, a rename may succeed even though nothing happened.
140 * Therefore, always unlink().
141 */
142 unlink(src);
143 } else if (opts & LN_FORCE) {
144 unlink(src);
145 }
146
147 link_func = link;
148 if (opts & LN_SYMLINK) {
149 link_func = symlink;
150 }
151
152 if (opts & LN_VERBOSE) {
153 printf("'%s' -> '%s'\n", src, *argv);
154 }
155
156 if (link_func(*argv, src) != 0) {
157 bb_simple_perror_msg(src);
158 status = EXIT_FAILURE;
159 }
160
161 free(src_name);
162 } while ((++argv)[1]);
163
164 return status;
165 }
166