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#if 0
33#ifndef lint
34static char const copyright[] =
35"@(#) Copyright (c) 1987, 1993, 1994\n\
36	The Regents of the University of California.  All rights reserved.\n";
37#endif /* not lint */
38
39#ifndef lint
40static char sccsid[] = "@(#)ln.c	8.2 (Berkeley) 3/31/94";
41#endif /* not lint */
42#endif
43#include <sys/cdefs.h>
44__FBSDID("$FreeBSD$");
45
46#include <sys/param.h>
47#include <sys/stat.h>
48
49#include <err.h>
50#include <errno.h>
51#include <fcntl.h>
52#include <libgen.h>
53#include <limits.h>
54#include <stdio.h>
55#include <stdlib.h>
56#include <string.h>
57#include <unistd.h>
58
59static int	fflag;			/* Unlink existing files. */
60static int	Fflag;			/* Remove empty directories also. */
61static int	hflag;			/* Check new name for symlink first. */
62static int	iflag;			/* Interactive mode. */
63static int	Pflag;			/* Create hard links to symlinks. */
64static int	sflag;			/* Symbolic, not hard, link. */
65static int	vflag;			/* Verbose output. */
66static int	wflag;			/* Warn if symlink target does not
67					 * exist, and -f is not enabled. */
68static char	linkch;
69
70static int	linkit(const char *, const char *, int);
71static void	usage(void);
72
73int
74main(int argc, char *argv[])
75{
76	struct stat sb;
77	char *p, *targetdir;
78	int ch, exitval;
79
80	/*
81	 * Test for the special case where the utility is called as
82	 * "link", for which the functionality provided is greatly
83	 * simplified.
84	 */
85	if ((p = strrchr(argv[0], '/')) == NULL)
86		p = argv[0];
87	else
88		++p;
89	if (strcmp(p, "link") == 0) {
90		while (getopt(argc, argv, "") != -1)
91			usage();
92		argc -= optind;
93		argv += optind;
94		if (argc != 2)
95			usage();
96		exit(linkit(argv[0], argv[1], 0));
97	}
98
99	while ((ch = getopt(argc, argv, "FLPfhinsvw")) != -1)
100		switch (ch) {
101		case 'F':
102			Fflag = 1;
103			break;
104		case 'L':
105			Pflag = 0;
106			break;
107		case 'P':
108			Pflag = 1;
109			break;
110		case 'f':
111			fflag = 1;
112			iflag = 0;
113			wflag = 0;
114			break;
115		case 'h':
116		case 'n':
117			hflag = 1;
118			break;
119		case 'i':
120			iflag = 1;
121			fflag = 0;
122			break;
123		case 's':
124			sflag = 1;
125			break;
126		case 'v':
127			vflag = 1;
128			break;
129		case 'w':
130			wflag = 1;
131			break;
132		case '?':
133		default:
134			usage();
135		}
136
137	argv += optind;
138	argc -= optind;
139
140	linkch = sflag ? '-' : '=';
141	if (sflag == 0)
142		Fflag = 0;
143	if (Fflag == 1 && iflag == 0) {
144		fflag = 1;
145		wflag = 0;		/* Implied when fflag != 0 */
146	}
147
148	switch(argc) {
149	case 0:
150		usage();
151		/* NOTREACHED */
152	case 1:				/* ln source */
153		exit(linkit(argv[0], ".", 1));
154	case 2:				/* ln source target */
155		exit(linkit(argv[0], argv[1], 0));
156	default:
157		;
158	}
159					/* ln source1 source2 directory */
160	targetdir = argv[argc - 1];
161	if (hflag && lstat(targetdir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
162		/*
163		 * We were asked not to follow symlinks, but found one at
164		 * the target--simulate "not a directory" error
165		 */
166		errno = ENOTDIR;
167		err(1, "%s", targetdir);
168	}
169	if (stat(targetdir, &sb))
170		err(1, "%s", targetdir);
171	if (!S_ISDIR(sb.st_mode))
172		usage();
173	for (exitval = 0; *argv != targetdir; ++argv)
174		exitval |= linkit(*argv, targetdir, 1);
175	exit(exitval);
176}
177
178/*
179 * Two pathnames refer to the same directory entry if the directories match
180 * and the final components' names match.
181 */
182static int
183samedirent(const char *path1, const char *path2)
184{
185	const char *file1, *file2;
186	char pathbuf[PATH_MAX];
187	struct stat sb1, sb2;
188
189	if (strcmp(path1, path2) == 0)
190		return 1;
191	file1 = strrchr(path1, '/');
192	if (file1 != NULL)
193		file1++;
194	else
195		file1 = path1;
196	file2 = strrchr(path2, '/');
197	if (file2 != NULL)
198		file2++;
199	else
200		file2 = path2;
201	if (strcmp(file1, file2) != 0)
202		return 0;
203	if (file1 - path1 >= PATH_MAX || file2 - path2 >= PATH_MAX)
204		return 0;
205	if (file1 == path1)
206		memcpy(pathbuf, ".", 2);
207	else {
208		memcpy(pathbuf, path1, file1 - path1);
209		pathbuf[file1 - path1] = '\0';
210	}
211	if (stat(pathbuf, &sb1) != 0)
212		return 0;
213	if (file2 == path2)
214		memcpy(pathbuf, ".", 2);
215	else {
216		memcpy(pathbuf, path2, file2 - path2);
217		pathbuf[file2 - path2] = '\0';
218	}
219	if (stat(pathbuf, &sb2) != 0)
220		return 0;
221	return sb1.st_dev == sb2.st_dev && sb1.st_ino == sb2.st_ino;
222}
223
224static int
225linkit(const char *source, const char *target, int isdir)
226{
227	struct stat sb;
228	const char *p;
229	int ch, exists, first;
230	char path[PATH_MAX];
231	char wbuf[PATH_MAX];
232	char bbuf[PATH_MAX];
233
234	if (!sflag) {
235		/* If source doesn't exist, quit now. */
236		if ((Pflag ? lstat : stat)(source, &sb)) {
237			warn("%s", source);
238			return (1);
239		}
240		/* Only symbolic links to directories. */
241		if (S_ISDIR(sb.st_mode)) {
242			errno = EISDIR;
243			warn("%s", source);
244			return (1);
245		}
246	}
247
248	/*
249	 * If the target is a directory (and not a symlink if hflag),
250	 * append the source's name, unless Fflag is set.
251	 */
252	if (!Fflag && (isdir ||
253	    (lstat(target, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
254	    (!hflag && stat(target, &sb) == 0 && S_ISDIR(sb.st_mode)))) {
255		if (strlcpy(bbuf, source, sizeof(bbuf)) >= sizeof(bbuf) ||
256		    (p = basename(bbuf)) == NULL ||
257		    snprintf(path, sizeof(path), "%s/%s", target, p) >=
258		    (ssize_t)sizeof(path)) {
259			errno = ENAMETOOLONG;
260			warn("%s", source);
261			return (1);
262		}
263		target = path;
264	}
265
266	/*
267	 * If the link source doesn't exist, and a symbolic link was
268	 * requested, and -w was specified, give a warning.
269	 */
270	if (sflag && wflag) {
271		if (*source == '/') {
272			/* Absolute link source. */
273			if (stat(source, &sb) != 0)
274				 warn("warning: %s inaccessible", source);
275		} else {
276			/*
277			 * Relative symlink source.  Try to construct the
278			 * absolute path of the source, by appending `source'
279			 * to the parent directory of the target.
280			 */
281			strlcpy(bbuf, target, sizeof(bbuf));
282			p = dirname(bbuf);
283			if (p != NULL) {
284				(void)snprintf(wbuf, sizeof(wbuf), "%s/%s",
285						p, source);
286				if (stat(wbuf, &sb) != 0)
287					warn("warning: %s", source);
288			}
289		}
290	}
291
292	/*
293	 * If the file exists, first check it is not the same directory entry.
294	 */
295	exists = !lstat(target, &sb);
296	if (exists) {
297		if (!sflag && samedirent(source, target)) {
298			warnx("%s and %s are the same directory entry",
299			    source, target);
300			return (1);
301		}
302	}
303	/*
304	 * Then unlink it forcibly if -f was specified
305	 * and interactively if -i was specified.
306	 */
307	if (fflag && exists) {
308		if (Fflag && S_ISDIR(sb.st_mode)) {
309			if (rmdir(target)) {
310				warn("%s", target);
311				return (1);
312			}
313		} else if (unlink(target)) {
314			warn("%s", target);
315			return (1);
316		}
317	} else if (iflag && exists) {
318		fflush(stdout);
319		fprintf(stderr, "replace %s? ", target);
320
321		first = ch = getchar();
322		while(ch != '\n' && ch != EOF)
323			ch = getchar();
324		if (first != 'y' && first != 'Y') {
325			fprintf(stderr, "not replaced\n");
326			return (1);
327		}
328
329		if (Fflag && S_ISDIR(sb.st_mode)) {
330			if (rmdir(target)) {
331				warn("%s", target);
332				return (1);
333			}
334		} else if (unlink(target)) {
335			warn("%s", target);
336			return (1);
337		}
338	}
339
340	/* Attempt the link. */
341	if (sflag ? symlink(source, target) :
342	    linkat(AT_FDCWD, source, AT_FDCWD, target,
343	    Pflag ? 0 : AT_SYMLINK_FOLLOW)) {
344		warn("%s", target);
345		return (1);
346	}
347	if (vflag)
348		(void)printf("%s %c> %s\n", target, linkch, source);
349	return (0);
350}
351
352static void
353usage(void)
354{
355	(void)fprintf(stderr, "%s\n%s\n%s\n",
356	    "usage: ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file [target_file]",
357	    "       ln [-s [-F] | -L | -P] [-f | -i] [-hnv] source_file ... target_dir",
358	    "       link source_file target_file");
359	exit(1);
360}
361