1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1987, 1993, 1994
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <sys/param.h>
33#include <sys/stat.h>
34
35#include <err.h>
36#include <errno.h>
37#include <fcntl.h>
38#include <libgen.h>
39#include <limits.h>
40#include <stdbool.h>
41#include <stdio.h>
42#include <stdlib.h>
43#include <string.h>
44#include <unistd.h>
45
46static bool	fflag;			/* Unlink existing files. */
47static bool	Fflag;			/* Remove empty directories also. */
48static bool	hflag;			/* Check new name for symlink first. */
49static bool	iflag;			/* Interactive mode. */
50static bool	Pflag;			/* Create hard links to symlinks. */
51static bool	sflag;			/* Symbolic, not hard, link. */
52static bool	vflag;			/* Verbose output. */
53static bool	wflag;			/* Warn if symlink target does not
54					 * exist, and -f is not enabled. */
55static char	linkch;
56
57static int	linkit(const char *, const char *, bool);
58static void	link_usage(void) __dead2;
59static void	usage(void) __dead2;
60
61int
62main(int argc, char *argv[])
63{
64	struct stat sb;
65	char *targetdir;
66	int ch, exitval;
67
68	/*
69	 * Test for the special case where the utility is called as
70	 * "link", for which the functionality provided is greatly
71	 * simplified.
72	 */
73	if (strcmp(getprogname(), "link") == 0) {
74		while (getopt(argc, argv, "") != -1)
75			link_usage();
76		argc -= optind;
77		argv += optind;
78		if (argc != 2)
79			link_usage();
80		if (lstat(argv[1], &sb) == 0)
81			errc(1, EEXIST, "%s", argv[1]);
82		/*
83		 * We could simply call link(2) here, but linkit()
84		 * performs additional checks and gives better
85		 * diagnostics.
86		 */
87		exit(linkit(argv[0], argv[1], false));
88	}
89
90	while ((ch = getopt(argc, argv, "FLPfhinsvw")) != -1)
91		switch (ch) {
92		case 'F':
93			Fflag = true;
94			break;
95		case 'L':
96			Pflag = false;
97			break;
98		case 'P':
99			Pflag = true;
100			break;
101		case 'f':
102			fflag = true;
103			iflag = false;
104			wflag = false;
105			break;
106		case 'h':
107		case 'n':
108			hflag = true;
109			break;
110		case 'i':
111			iflag = true;
112			fflag = false;
113			break;
114		case 's':
115			sflag = true;
116			break;
117		case 'v':
118			vflag = true;
119			break;
120		case 'w':
121			wflag = true;
122			break;
123		case '?':
124		default:
125			usage();
126		}
127
128	argv += optind;
129	argc -= optind;
130
131	linkch = sflag ? '-' : '=';
132	if (!sflag)
133		Fflag = false;
134	if (Fflag && !iflag) {
135		fflag = true;
136		wflag = false;		/* Implied when fflag is true */
137	}
138
139	switch (argc) {
140	case 0:
141		usage();
142		/* NOTREACHED */
143	case 1:				/* ln source */
144		exit(linkit(argv[0], ".", true));
145	case 2:				/* ln source target */
146		exit(linkit(argv[0], argv[1], false));
147	default:
148		;
149	}
150					/* ln source1 source2 directory */
151	targetdir = argv[argc - 1];
152	if (hflag && lstat(targetdir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
153		/*
154		 * We were asked not to follow symlinks, but found one at
155		 * the target--simulate "not a directory" error
156		 */
157		errno = ENOTDIR;
158		err(1, "%s", targetdir);
159	}
160	if (stat(targetdir, &sb))
161		err(1, "%s", targetdir);
162	if (!S_ISDIR(sb.st_mode))
163		usage();
164	for (exitval = 0; *argv != targetdir; ++argv)
165		exitval |= linkit(*argv, targetdir, true);
166	exit(exitval);
167}
168
169/*
170 * Two pathnames refer to the same directory entry if the directories match
171 * and the final components' names match.
172 */
173static int
174samedirent(const char *path1, const char *path2)
175{
176	const char *file1, *file2;
177	char pathbuf[PATH_MAX];
178	struct stat sb1, sb2;
179
180	if (strcmp(path1, path2) == 0)
181		return 1;
182	file1 = strrchr(path1, '/');
183	if (file1 != NULL)
184		file1++;
185	else
186		file1 = path1;
187	file2 = strrchr(path2, '/');
188	if (file2 != NULL)
189		file2++;
190	else
191		file2 = path2;
192	if (strcmp(file1, file2) != 0)
193		return 0;
194	if (file1 - path1 >= PATH_MAX || file2 - path2 >= PATH_MAX)
195		return 0;
196	if (file1 == path1)
197		memcpy(pathbuf, ".", 2);
198	else {
199		memcpy(pathbuf, path1, file1 - path1);
200		pathbuf[file1 - path1] = '\0';
201	}
202	if (stat(pathbuf, &sb1) != 0)
203		return 0;
204	if (file2 == path2)
205		memcpy(pathbuf, ".", 2);
206	else {
207		memcpy(pathbuf, path2, file2 - path2);
208		pathbuf[file2 - path2] = '\0';
209	}
210	if (stat(pathbuf, &sb2) != 0)
211		return 0;
212	return sb1.st_dev == sb2.st_dev && sb1.st_ino == sb2.st_ino;
213}
214
215static int
216linkit(const char *source, const char *target, bool isdir)
217{
218	char path[PATH_MAX];
219	char wbuf[PATH_MAX];
220	char bbuf[PATH_MAX];
221	struct stat sb;
222	const char *p;
223	int ch, first;
224	bool exists;
225
226	if (!sflag) {
227		/* If source doesn't exist, quit now. */
228		if ((Pflag ? lstat : stat)(source, &sb)) {
229			warn("%s", source);
230			return (1);
231		}
232		/* Only symbolic links to directories. */
233		if (S_ISDIR(sb.st_mode)) {
234			errno = EISDIR;
235			warn("%s", source);
236			return (1);
237		}
238	}
239
240	/*
241	 * If the target is a directory (and not a symlink if hflag),
242	 * append the source's name, unless Fflag is set.
243	 */
244	if (!Fflag && (isdir ||
245	    (lstat(target, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
246	    (!hflag && stat(target, &sb) == 0 && S_ISDIR(sb.st_mode)))) {
247		if (strlcpy(bbuf, source, sizeof(bbuf)) >= sizeof(bbuf) ||
248		    (p = basename(bbuf)) == NULL ||
249		    snprintf(path, sizeof(path), "%s/%s", target, p) >=
250		    (ssize_t)sizeof(path)) {
251			errno = ENAMETOOLONG;
252			warn("%s", source);
253			return (1);
254		}
255		target = path;
256	}
257
258	/*
259	 * If the link source doesn't exist, and a symbolic link was
260	 * requested, and -w was specified, give a warning.
261	 */
262	if (sflag && wflag) {
263		if (*source == '/') {
264			/* Absolute link source. */
265			if (stat(source, &sb) != 0)
266				 warn("warning: %s inaccessible", source);
267		} else {
268			/*
269			 * Relative symlink source.  Try to construct the
270			 * absolute path of the source, by appending `source'
271			 * to the parent directory of the target.
272			 */
273			strlcpy(bbuf, target, sizeof(bbuf));
274			p = dirname(bbuf);
275			if (p != NULL) {
276				(void)snprintf(wbuf, sizeof(wbuf), "%s/%s",
277						p, source);
278				if (stat(wbuf, &sb) != 0)
279					warn("warning: %s", source);
280			}
281		}
282	}
283
284	/*
285	 * If the file exists, first check it is not the same directory entry.
286	 */
287	exists = lstat(target, &sb) == 0;
288	if (exists) {
289		if (!sflag && samedirent(source, target)) {
290			warnx("%s and %s are the same directory entry",
291			    source, target);
292			return (1);
293		}
294	}
295	/*
296	 * Then unlink it forcibly if -f was specified
297	 * and interactively if -i was specified.
298	 */
299	if (fflag && exists) {
300		if (Fflag && S_ISDIR(sb.st_mode)) {
301			if (rmdir(target)) {
302				warn("%s", target);
303				return (1);
304			}
305		} else if (unlink(target)) {
306			warn("%s", target);
307			return (1);
308		}
309	} else if (iflag && exists) {
310		fflush(stdout);
311		fprintf(stderr, "replace %s? ", target);
312
313		first = ch = getchar();
314		while(ch != '\n' && ch != EOF)
315			ch = getchar();
316		if (first != 'y' && first != 'Y') {
317			fprintf(stderr, "not replaced\n");
318			return (1);
319		}
320
321		if (Fflag && S_ISDIR(sb.st_mode)) {
322			if (rmdir(target)) {
323				warn("%s", target);
324				return (1);
325			}
326		} else if (unlink(target)) {
327			warn("%s", target);
328			return (1);
329		}
330	}
331
332	/* Attempt the link. */
333	if (sflag ? symlink(source, target) :
334	    linkat(AT_FDCWD, source, AT_FDCWD, target,
335	    Pflag ? 0 : AT_SYMLINK_FOLLOW)) {
336		warn("%s", target);
337		return (1);
338	}
339	if (vflag)
340		(void)printf("%s %c> %s\n", target, linkch, source);
341	return (0);
342}
343
344static void
345link_usage(void)
346{
347	(void)fprintf(stderr, "usage: link source_file target_file\n");
348	exit(1);
349}
350
351static void
352usage(void)
353{
354	(void)fprintf(stderr, "%s\n%s\n",
355	    "usage: ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file [target_file]",
356	    "       ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file ... target_dir");
357	exit(1);
358}
359